WO2016197323A1 - 视频编解码方法和视频编解码器 - Google Patents

视频编解码方法和视频编解码器 Download PDF

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Publication number
WO2016197323A1
WO2016197323A1 PCT/CN2015/081066 CN2015081066W WO2016197323A1 WO 2016197323 A1 WO2016197323 A1 WO 2016197323A1 CN 2015081066 W CN2015081066 W CN 2015081066W WO 2016197323 A1 WO2016197323 A1 WO 2016197323A1
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image block
photoelectric conversion
image
electro
conversion function
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English (en)
French (fr)
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陈海
李蒙
郑萧桢
郑建铧
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Huawei Technologies Co Ltd
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Huawei Technologies Co Ltd
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Priority to PCT/CN2015/081066 priority Critical patent/WO2016197323A1/zh
Priority to CN201580077349.8A priority patent/CN107409223B/zh
Priority to JP2017564005A priority patent/JP2018524875A/ja
Priority to KR1020187000396A priority patent/KR20180015248A/ko
Priority to EP15894593.1A priority patent/EP3300368A4/en
Publication of WO2016197323A1 publication Critical patent/WO2016197323A1/zh
Priority to US15/835,771 priority patent/US20180103258A1/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/134—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or criterion affecting or controlling the adaptive coding
    • H04N19/136—Incoming video signal characteristics or properties
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/186—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being a colour or a chrominance component
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/124—Quantisation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/17—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object
    • H04N19/176—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being an image region, e.g. an object the region being a block, e.g. a macroblock
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/182—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being a pixel
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/189—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the adaptation method, adaptation tool or adaptation type used for the adaptive coding
    • H04N19/196—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the adaptation method, adaptation tool or adaptation type used for the adaptive coding being specially adapted for the computation of encoding parameters, e.g. by averaging previously computed encoding parameters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/46—Embedding additional information in the video signal during the compression process
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/90—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using coding techniques not provided for in groups H04N19/10-H04N19/85, e.g. fractals
    • H04N19/98—Adaptive-dynamic-range coding [ADRC]

Definitions

  • Embodiments of the present invention relate to the field of video coding and decoding, and more particularly, to a video codec method and a video codec.
  • the Dynamic Range is used to represent the ratio of the maximum and minimum values of a variable.
  • the dynamic range represents the ratio between the maximum and minimum brightness values within the range in which the image can be displayed.
  • the dynamic range of the brightness of the natural world is in the range of 10 -3 to 10 6 .
  • each channel of R, G, and B is stored by one byte (8 bits), that is, the brightness range of each channel is 0 to 255, where 0 to 255 are numbers.
  • the dynamic range of the image is 8 bits.
  • the dynamic range of nature is in the range of 10 -3 to 10 6 , which is much higher than the dynamic range of digital images, we can call the dynamic range of nature as High Dynamic Range (HDR).
  • the dynamic range of a normal digital image is Low Dynamic Range (LDR).
  • the imaging process of a digital camera is actually a mapping of the high dynamic range of nature to the low dynamic range of digital images. This is often a non-linear mapping process.
  • HDR Image is an image that can represent a high dynamic range change. Since the HDR image needs to represent the visible range of brightness of the human eye, each color channel of the HDR image requires more data bits than the conventional image. For example, pixels of an HDR image are often represented using 16-bit "half precision" or 32-bit floating point numbers.
  • the information stored in the HDR image is generally the real illumination information of nature, and the unit is cd/m 2 , but the maximum illumination supported by the display device is limited, and the true illumination of the natural world cannot be completely reflected. Since people need to browse images through a display device, it is necessary to convert the illumination information stored in the HDR image into an electrical signal that can be displayed by the display device by using an Optical-Electro Transfer Function (OETF).
  • OETF Optical-Electro Transfer Function
  • the photoelectric conversion function was originally applied to the traditional cathode ray tube (CRT) display device.
  • the photoelectric conversion function can well match the illumination information with the brightness value of the CRT display device.
  • the photoelectric conversion function here can be It is a general term from the light information to the electrical signal conversion function of the display device. Therefore, the conversion effect of the photoelectric conversion function directly determines the display effect of the HDR image on the display device.
  • the HDR video coding generally performs operations such as photoelectric conversion, color space conversion, quantization, and video encoding on the HDR image frames in the HDR video stream in units of HDR image frames. Specifically, first, the input HDR image frame is photoelectrically converted; then, the RGB information of the converted HDR image frame is converted into a YCbCr space; the data information of the image is quantized in the YCbCr space; and finally, the video encoding is performed based on the quantized data. .
  • the HDR video is decoded into the inverse process of the above process, that is, the code stream is first decoded to obtain decoded data, and then the decoded data is converted into [0, 1] floating point data through inverse quantization operation; YCbCr is converted by color space conversion. The spatial data is converted to the RGB color space; finally, the RGB color information is converted to a 16-bit or 32-bit floating point number by an Electro-Optical Transfer Function (EOTF) to represent real-world luminance information.
  • EOTF Electro-Optical Transfer Function
  • the ISO standard proposes a specific HDR coding scheme "ISO/IEC JTC1/SC29/WG11 MPEG2014/N15083".
  • the photoelectric conversion process at the encoding end and the specific form of the photoelectric conversion function PQ_TF used are as shown in the following formula (1):
  • a graph of the photoelectric conversion function PQ_TF is shown in FIG.
  • the electro-optic at the decoding end The conversion process and the specific form of the electro-optical conversion function inversePQ_FT (the inverse of PQ_TF) used are shown in the following formula (2):
  • the photoelectric conversion function in the above scheme is a global photoelectric conversion function, that is, the pixels of the entire HDR image frame are converted by the above photoelectric conversion function, but the luminance information of different image regions (for example, foreground and background regions) is different, and the entire frame image is Both use the same photoelectric conversion function without considering the spatial locality of the image, resulting in poor HDR video coding.
  • Embodiments of the present invention provide a video encoding and decoding method and a video codec to improve the effect of HDR video coding.
  • a video encoding method comprising: acquiring an HDR image frame to be encoded, wherein the HDR image frame includes a plurality of image blocks; according to brightness of each of the plurality of image blocks a statistic value, determining a photoelectric conversion function corresponding to each image block from a plurality of preset photoelectric conversion functions; performing photoelectric conversion on each image block according to a photoelectric conversion function corresponding to each image block; The plurality of image blocks after photoelectric conversion are encoded.
  • the determining, according to a statistical value of a brightness of each of the plurality of image blocks, from the preset plurality of photoelectric conversion functions a photoelectric conversion function corresponding to each image block comprising: statistics according to brightness of each image block a value, respectively determining a function value of the preset plurality of photoelectric conversion functions; selecting, from the function values of the plurality of photoelectric conversion functions, an objective function value having a smallest difference from the preset value; and corresponding to the target function value
  • the photoelectric conversion function is determined as a photoelectric conversion function corresponding to each of the image blocks.
  • the determining, according to a statistic value of a brightness of each of the plurality of image blocks, from a preset Determining a photoelectric conversion function corresponding to each image block in the plurality of photoelectric conversion functions comprising: determining a first numerical interval into which a statistical value of brightness of each image block falls, wherein the first numerical value The interval is one of a plurality of preset numerical intervals; and the photoelectric conversion function corresponding to the first numerical interval is determined as the one according to a one-to-one correspondence between the plurality of numerical intervals and the plurality of photoelectric conversion functions The luminance statistical value falls within a photoelectric conversion function corresponding to each image block in the first numerical interval.
  • the encoding, the photoelectrically converted plurality of image blocks including: in units of 8 bits And quantizing the plurality of image blocks after photoelectric conversion to obtain quantized data of the plurality of image blocks; and encoding according to the quantized data of the plurality of image blocks.
  • the method further includes: writing, to the code stream, the photoelectric conversion information of each image block, where The photoelectric conversion information is used by the decoding end to determine an electro-optical conversion function of the decoding block corresponding to each image block.
  • the photoelectric conversion information includes at least one of the following information of each image block: each of An index of the photoelectric conversion function corresponding to each of the image blocks; a statistical value of the brightness of each of the image blocks; and a parameter of the photoelectric conversion function corresponding to each of the image blocks.
  • the statistic value is a brightness average value, a luminance variance, and a maximum brightness value of the pixel points in each image block. Histogram statistics for minimum brightness values or brightness.
  • At least two of the plurality of image blocks correspond to the same photoelectric conversion function.
  • the determining, according to a statistic value of a brightness of each of the plurality of image blocks, from a preset Determining, in the plurality of photoelectric conversion functions, the photoelectric conversion function corresponding to each of the image blocks comprises: Determining, according to a statistical value of the brightness of any one of the plurality of image blocks, a photoelectric conversion function corresponding to the first image block; determining an image block remaining in addition to the first image block and the first Correlation of brightness between image blocks; determining, based on the determined brightness correlation, whether the remaining image blocks share the same photoelectric conversion function as the first image block; when determining the remaining image blocks and When the first image blocks share the same photoelectric conversion function, the photoelectric conversion function corresponding to the first image block is determined as a global photoelectric conversion function corresponding to the HDR image frame; when it is determined that the remaining image blocks exist When the image block of the same photoelectric conversion function cannot be shared with
  • a video decoding method comprising: decoding a code stream to reconstruct a high dynamic range HDR image frame, the HDR image frame comprising a plurality of image blocks; and obtaining each of the plurality of image blocks from the code stream Photoelectric conversion information of the image blocks, the photoelectric conversion information being determined by the encoding end based on a statistical value of the brightness of the coding block corresponding to each image block, and the photoelectric conversion information is used by the decoding end to determine each of the images And an electro-optical conversion function corresponding to the block; determining, according to the photoelectric conversion information of each image block, an electro-optical conversion function corresponding to each image block from a preset plurality of electro-optic conversion functions; corresponding to each image block And an electro-optical conversion function for performing electro-optical conversion on each of the image blocks.
  • the photoelectric conversion information includes index information for indicating an index of an electro-optical conversion function of each image block, wherein the index information is the
  • the encoding end determines, according to the index of the photoelectric conversion function corresponding to each image block, the image block is determined from a preset plurality of electro-optical conversion functions according to the photoelectric conversion information of each image block.
  • Corresponding electro-optical conversion function includes: determining an electro-optical conversion function corresponding to each image block from the preset plurality of electro-optical conversion functions according to an index of an electro-optical conversion function of each image block.
  • the photoelectric conversion information includes a statistical value of a brightness of the coding block corresponding to each image block, Determining, according to the photoelectric conversion information of each image block, an electro-optic conversion function corresponding to each image block from a preset plurality of electro-optical conversion functions, including: determining, according to the brightness of the coding block corresponding to each image block a statistical value, respectively determining a function value of the preset plurality of electro-optical conversion functions; selecting, from the function values of the plurality of electro-optical conversion functions, an objective function value having a smallest difference from the preset value; and the objective function value Corresponding electro-optic conversion function is determined as the electro-optic corresponding to each image block Conversion function.
  • the photoelectric conversion information includes a statistical value of a brightness of the coding block corresponding to each image block, Determining, according to the photoelectric conversion information of each image block, the electro-optical conversion function corresponding to each image block from the preset plurality of electro-optical conversion functions, including: determining a brightness of the coding block corresponding to each image block a first numerical interval in which the statistical value falls, wherein the first numerical interval is one of a plurality of preset numerical intervals; and the plurality of numerical intervals and the plurality of electro-optical conversion functions are one by one Corresponding relationship, determining an electro-optical conversion function corresponding to the first numerical interval as an electro-optical conversion function corresponding to each image block.
  • the photoelectric conversion information includes a statistical value of a brightness of the coding block corresponding to each image block, Determining, according to the photoelectric conversion information of each image block, the electro-optical conversion function corresponding to each image block from the preset plurality of electro-optical conversion functions, including: first, according to any one of the plurality of image blocks Determining, according to a statistical value of the brightness of the coding block corresponding to the image block, an electro-optical conversion function corresponding to the first image block; determining a coding block corresponding to the image block remaining except the first image block, and the first image block Corresponding to the brightness between the corresponding coded blocks; determining, based on the determined brightness correlation, whether the remaining image blocks share the same electro-optical transfer function with the first image block; when determining the remaining image blocks When sharing the same electro-optical conversion function with the first image block, determining an electro-optical conversion function
  • the photoelectric conversion information includes at least one of the following information of each image block: Index information of an index of an electro-optical conversion function corresponding to each image block; information for indicating parameters of an electro-optic conversion function corresponding to each image block; and brightness of a coding block corresponding to each image block Statistics.
  • the statistic value is a luminance mean value and a luminance variance of a pixel point in the coding block corresponding to each image block. Histogram statistics for maximum brightness value, minimum brightness value, or brightness.
  • a third aspect provides a video encoder, including: an acquiring unit, configured to acquire a to-be-encoded An HDR image frame, wherein the HDR image frame includes a plurality of image blocks; a determining unit configured to preset a plurality of photoelectric conversion functions according to a statistical value of brightness of each of the plurality of image blocks Determining a photoelectric conversion function corresponding to each image block; a photoelectric conversion unit, configured to perform photoelectric conversion on each image block according to a photoelectric conversion function corresponding to each image block; and an encoding unit configured to The plurality of image blocks after photoelectric conversion are encoded.
  • the determining unit is specifically configured to determine, according to a statistical value of the brightness of each image block, a function of the preset plurality of photoelectric conversion functions a value; an objective function value having a smallest difference from the preset value is selected from the function values of the plurality of photoelectric conversion functions; and a photoelectric conversion function corresponding to the target function value is determined as a photoelectric conversion function corresponding to each image block .
  • the determining unit is specifically configured to determine a statistic value of the brightness of each image block a numerical interval, wherein the first numerical interval is one of a plurality of preset numerical intervals; and the first is performed according to a one-to-one correspondence between the plurality of numerical intervals and the plurality of photoelectric conversion functions
  • the photoelectric conversion function corresponding to the numerical interval is determined as a photoelectric conversion function corresponding to each image block in which the luminance statistical value falls within the first numerical interval.
  • the coding unit is specifically configured to perform the photoelectrically converted multiple images in units of 8 bits
  • the block is quantized to obtain quantized data of the plurality of image blocks; and encoded according to the quantized data of the plurality of image blocks.
  • the video encoder further includes: a writing unit, configured to write the each into the code stream The photoelectric conversion information of the image block is used by the decoding end to determine an electro-optical conversion function of the decoding block corresponding to each image block.
  • the photoelectric conversion information includes at least one of the following information of each image block: An index of the photoelectric conversion function corresponding to each of the image blocks; a statistical value of the brightness of each of the image blocks; and a parameter of the photoelectric conversion function corresponding to each of the image blocks.
  • the statistical value is a brightness average value, a luminance variance, and a maximum brightness value of the pixel points in each image block. Histogram statistics for minimum brightness values or brightness.
  • At least two of the plurality of image blocks correspond to the same photoelectric conversion function.
  • the determining unit is specifically configured to use, according to the brightness of the first image block of any one of the plurality of image blocks a statistical value, determining a photoelectric conversion function corresponding to the first image block; determining a correlation of brightness between the image block remaining except the first image block and the first image block; a brightness correlation, determining whether the remaining image blocks share the same photoelectric conversion function as the first image block; when it is determined that the remaining image blocks share the same photoelectric conversion function as the first image block,
  • the photoelectric conversion function corresponding to the first image block is determined as a global photoelectric conversion function corresponding to the HDR image frame; when it is determined that there is an image in the remaining image block that cannot share the same photoelectric conversion function as the first image block
  • the photoelectric conversion function corresponding to each of the remaining image blocks is determined according to the statistical value of the brightness of the remaining images.
  • a video decoder comprising: a decoding unit, configured to decode a code stream to reconstruct a high dynamic range HDR image frame, the HDR image frame includes a plurality of image blocks; and an acquiring unit, configured to And acquiring, in the stream, photoelectric conversion information of each of the plurality of image blocks, the photoelectric conversion information being determined by the encoding end based on a statistical value of a brightness of the coding block corresponding to each of the image blocks, and the photoelectric conversion information Determining, by the decoding end, an electro-optical conversion function corresponding to each of the image blocks; determining unit, configured to determine each of the plurality of electro-optical conversion functions from the preset plurality of electro-optical conversion functions according to the photoelectric conversion information of each of the image blocks An electro-optic conversion function corresponding to the block, and an electro-optical conversion unit configured to perform electro-optical conversion on each of the image blocks according to an electro-optical conversion function corresponding to each of the image blocks
  • the photoelectric conversion information includes index information for indicating an index of an electro-optical conversion function of each image block, wherein the index information is the The encoding end is determined based on an index of the photoelectric conversion function corresponding to each image block, and the determining unit is specifically configured to convert from the preset plurality of electro-optical lights according to an index of an electro-optic conversion function of each image block.
  • An electro-optic conversion function corresponding to each image block is determined in the function.
  • the photoelectric conversion information includes a statistical value of a brightness of the coding block corresponding to each image block
  • the determining unit is configured to determine, according to a statistical value of the brightness of the coding block corresponding to each image block, a function value of the preset plurality of electro-optical conversion functions; and from a function value of the plurality of electro-optical conversion functions Selecting an objective function value that has the smallest difference from the preset value; corresponding to the target function value
  • An electro-optical conversion function is determined as an electro-optical conversion function corresponding to each of the image blocks.
  • the photoelectric conversion information includes a statistical value of a brightness of the coding block corresponding to each image block
  • the determining unit is specifically configured to determine a first value interval in which the statistical value of the brightness of the coding block corresponding to each image block falls, wherein the first value interval is one of a preset plurality of value intervals; And determining, according to the one-to-one correspondence between the plurality of numerical intervals and the plurality of electro-optic conversion functions, an electro-optic conversion function corresponding to the first numerical interval as an electro-optical conversion function corresponding to each image block.
  • the photoelectric conversion information includes a statistical value of a brightness of the coding block corresponding to each image block, Determining, by the determining unit, determining an electro-optical conversion function corresponding to the first image block according to a statistical value of a brightness of the coding block corresponding to any one of the plurality of image blocks; determining, in addition to the first image Correlating the brightness between the coded block corresponding to the remaining image block and the coded block corresponding to the first image block; determining, according to the determined brightness correlation, whether the remaining image block is related to the first An image block shares the same electro-optic conversion function; when it is determined that the remaining image block shares the same electro-optic conversion function with the first image block, determining an electro-optical conversion function corresponding to the first image block as the HDR a global electro-optic conversion function corresponding to the image frame; when it is determined that there is an image block in the remaining image block that
  • the photoelectric conversion information includes at least one of the following information of each image block: Index information of an index of an electro-optical conversion function corresponding to each image block; information for indicating parameters of an electro-optic conversion function corresponding to each image block; and brightness of a coding block corresponding to each image block Statistics.
  • the statistic value is a luminance mean value and a luminance variance of a pixel point in the coding block corresponding to each image block. Histogram statistics for maximum brightness value, minimum brightness value, or brightness.
  • the HDR image frame is divided into a plurality of image blocks, and then the photoelectric conversion function corresponding to each image block is selected from a preset plurality of photoelectric conversion functions according to the statistical value of the brightness of each image block.
  • the photoelectric conversion function of an image block is based on the local brightness of the image block itself.
  • the photoelectric conversion function of different image blocks may be the same or different, and the spatial locality of the image is fully considered compared with the method of using a global photoelectric conversion function in the entire frame image in the prior art. Improve the effect of HDR video encoding.
  • Fig. 1 is a graph of a conventional photoelectric conversion function.
  • FIG. 2 is a schematic flowchart of a video encoding method according to an embodiment of the present invention.
  • FIG. 3 is a graph of a plurality of preset photoelectric conversion functions of an embodiment of the present invention.
  • FIG. 4 is a schematic flowchart of a video decoding method according to an embodiment of the present invention.
  • FIG. 5 is a graph of a plurality of preset electro-optical conversion functions according to an embodiment of the present invention.
  • FIG. 6 is a schematic block diagram of a video encoder according to an embodiment of the present invention.
  • FIG. 7 is a schematic block diagram of a video decoder according to an embodiment of the present invention.
  • FIG. 8 is a schematic block diagram of a video encoder according to an embodiment of the present invention.
  • FIG. 9 is a schematic block diagram of a video decoder in accordance with an embodiment of the present invention.
  • FIG. 2 is a schematic flowchart of a video encoding method according to an embodiment of the present invention.
  • the method of Figure 2 can be performed by a video encoder.
  • the method of Figure 2 includes:
  • the HDR image frame described above may be any image frame acquired from an HDR video stream.
  • Each color component (or channel) of a pixel in the HDR image frame may be a 16-bit or 32-bit floating point number to represent real-world luminance information.
  • the pixels in the HDR image frame can be represented by RGB, and the unit can be cd/m 2 .
  • the above statistical value may be the brightness average of the pixel points in each image block, the luminance variance of the pixel points in each image block, the maximum brightness value of the pixel points in each image block, and the pixel points in each image block.
  • the luminance component of the HDR image is more important than the chrominance component, and the luminance component is more reflective of the local and overall illuminance characteristics of the scene.
  • the embodiment of the present invention may firstly apply to each image block of the HDR image frame. The brightness is statistically analyzed to obtain a statistical value of the brightness of each image block.
  • the preset plurality of photoelectric conversion functions in the embodiment of the present invention may be selected from the photoelectric conversion functions in the prior art, or may be obtained by adjusting the values of the parameters of a certain photoelectric conversion function in the prior art.
  • the value of the index m 2 in the formula (1) can be adjusted, and the values of 48.8, 78.8, 128.8, 168.8, 208.8, and 258.8 are respectively assigned to m 2 to obtain six photoelectric conversion functions as shown in FIG. The larger the m 2 value, the smoother the front of the curve.
  • the specific photoelectric conversion operation can be performed according to the prior art, such as establishing a look-up table, and performing photoelectric conversion by means of piecewise linear fitting, etc. Narration.
  • Step 240 may include: converting the photoelectrically converted plurality of image blocks from a current color space (such as RGB space or YUV space) to a YCbCr space; and in the YCbCr space, data of a plurality of image blocks in units of 8 bits or 10 bits The information is quantized and encoded using the quantized data.
  • a current color space such as RGB space or YUV space
  • YCbCr space data of a plurality of image blocks in units of 8 bits or 10 bits
  • the photoelectric conversion function corresponding to each image block is selected from a preset plurality of photoelectric conversion functions according to the statistical value of the brightness of each image block.
  • the photoelectric conversion function of an image block is determined based on the brightness of the image block itself, and the photoelectric conversion functions of different image blocks may be the same or different, and a global photoelectric conversion is used with the entire frame image in the prior art.
  • the spatial locality of the image is fully considered, and the effect of HDR video coding can be improved.
  • the existing video image coding framework generally performs the process of dividing the image into blocks.
  • a corresponding photoelectric conversion function is set for each image block, which can better match the existing video coding framework. adapt.
  • the step 220 may include: determining, according to a statistical value of the brightness of each image block, a function value of the preset plurality of photoelectric conversion functions; selecting a function value of the plurality of photoelectric conversion functions. The objective function value having the smallest difference from the preset value; the photoelectric conversion function corresponding to the objective function value is determined as the photoelectric conversion function corresponding to each image block.
  • the statistical value of the above brightness can be selected as the mean value of the brightness of each image block.
  • the brightness average value can be normalized first, and then the brightness average value is substituted into the six photoelectric conversion functions shown in Fig. 3 to obtain six function values.
  • the above preset value can be set to 0.8, that is, the photoelectric conversion function whose function value is closest to 0.8 can be regarded as the optimal photoelectric conversion function.
  • the optimal photoelectric conversion function can be selected as the photoelectric conversion function corresponding to each image block.
  • step 220 may include: determining a first value interval in which a statistical value of the brightness of each image block falls, wherein the first value interval is one of a preset plurality of numerical intervals And determining, according to the one-to-one correspondence between the plurality of numerical intervals and the plurality of photoelectric conversion functions, the photoelectric conversion function corresponding to the first numerical interval as the photoelectric conversion function corresponding to each image block in which the luminance statistical value falls within the first numerical interval; .
  • the photoelectric conversion function will have a data of [0-0.1] interval (corresponding to a luminance of 0-1000 cd/m 2 ). Mapped to the 0-0.7 interval, the data for the (0.1-1) interval can only be mapped to a cell between 0.7-1, which will result in a large amount of information loss, such as data with a brightness range of 2023-2050 cd/m2. It may be mapped to 0.8, and the details of the image in this luminance range are lost.
  • the HDR encoding method does not follow the existing frame in the form of 8-bit quantization, but will quantize The number of bits is extended to 10 bits, which reduces the loss of data to a certain extent, but increases the complexity of coding, resulting in waste of resources and incompatibility with existing coding frameworks.
  • the step 240 may include: quantizing the plurality of image blocks after photoelectric conversion in units of 8 bits to obtain quantized data of the plurality of image blocks; according to the plurality of image blocks The quantized data is encoded.
  • quantizing a plurality of image blocks after photoelectric conversion in units of 8 bits may mean that each color component of each pixel in the HDR image frame is quantized into data of 8-bit size.
  • the image block is used instead of the entire image frame for photoelectric conversion, the image is The brightness range of the block is smaller than the brightness range of the entire image frame.
  • the 8-bit quantization method can satisfy the requirement that no large amount of image information will be lost, so it can continue to be quantized in units of 8 bits. This makes it better compatible with existing coding frameworks.
  • the method of FIG. 2 may further include: writing photoelectric conversion information of each image block to the code stream, where the photoelectric conversion information is used by the decoding end to determine the electro-optic light of the decoding block corresponding to each image block. Conversion function.
  • the photoelectric conversion information may include at least one of the following information of each image block: an index of a photoelectric conversion function corresponding to each image block; a statistical value of brightness of each image block; And parameters of the photoelectric conversion function corresponding to each image block.
  • N photoelectric conversion functions are provided at the encoding end
  • N electro-optical conversion functions are provided at the decoding end
  • the N electro-optical conversion functions are inverse functions of N photoelectric conversion functions of the encoding end, respectively.
  • the N photoelectric conversion functions in the encoding end have an index
  • the N electro-optic conversion functions in the decoding end also have an index
  • the indices of the photoelectric conversion functions and the electro-optic conversion functions which are mutually inverse functions are the same.
  • the index of the photoelectric conversion function can be written into the code stream and transmitted to the decoding end.
  • the decoding end decodes the decoding block corresponding to the image block
  • the corresponding electro-optical conversion function can be found according to the index.
  • At least two of the plurality of image blocks correspond to the same photoelectric conversion function.
  • the step 220 may include: determining a photoelectric conversion function corresponding to the first image block according to a statistical value of the brightness of the first image block of any one of the plurality of image blocks; determining that the first image block is excluded Correlation of brightness between the remaining image blocks and the first image block; determining, based on the determined brightness correlation, whether the remaining image blocks share the same photoelectric conversion function as the first image block; when determining the remaining images
  • the photoelectric conversion function corresponding to the first image block is determined as a global photoelectric conversion function corresponding to the HDR image frame; when it is determined that the remaining image block exists and the first image block cannot exist
  • the photoelectric conversion functions corresponding to the respective remaining image blocks are determined based on the statistical values of the brightness of the remaining images.
  • determining the photoelectric conversion function corresponding to the first image block as the global photoelectric conversion function corresponding to the HDR image frame means that when the remaining image blocks have strong correlation with the first image block,
  • the image blocks specify a photoelectric conversion function, and it is only necessary to assign a global photoelectric conversion function to the entire HDR image frame as in the prior art, which can save the calculation amount of the encoding end and reduce the data amount of the code stream.
  • determining the photoelectric conversion function corresponding to each of the remaining image blocks according to the statistical value of the brightness of the remaining image means: when remaining When there are image blocks having weaker correlation with the first image block in the image block, each of the remaining image blocks determines their respective photoelectric conversion functions in the same manner as the first image block.
  • the embodiment of the present invention selects whether to use the global photoelectric conversion function or the respective photoelectric conversion function for each image block by judging the correlation between the image blocks, so that the encoding mode of the encoding end is more flexible.
  • the step 220 may include: determining a photoelectric conversion function corresponding to the first image block according to a statistical value of the brightness of the first image block of any one of the plurality of image blocks; determining that the first image block is excluded Correlation of brightness between the remaining image block and the first image block; determining a photoelectric conversion function of the target image block in the remaining image block as the first image according to the determined correlation of the brightness a photoelectric conversion function corresponding to the block, wherein a correlation between the target image block and the first image block is greater than a preset threshold.
  • the photoelectric conversion function of the image block having strong correlation with the first image block is conveniently obtained, and the computational complexity of the encoding end is reduced.
  • FIG. 2 a video encoding method according to an embodiment of the present invention is described in detail from the perspective of an encoding end.
  • a video decoding method according to an embodiment of the present invention will be described below from the perspective of a decoding end in conjunction with FIG.
  • the encoding end corresponds to the functions, operations, and characteristics of the decoding end, and the repeated description is omitted as appropriate for brevity.
  • FIG. 4 is a schematic flowchart of a video decoding method according to an embodiment of the present invention.
  • the method of Figure 4 can be performed by a decoder.
  • the method of Figure 4 includes:
  • the electro-optical conversion function corresponding to each image block needs to be determined by using the photoelectric conversion information transmitted from the encoding end, and the photoelectric conversion information may be part or all of the luminance statistical information obtained by the encoding end, or may be
  • the index of the electro-optic conversion function corresponding to each image block may also be a parameter of the electro-optic conversion function corresponding to each image block (requiring the encoding end to inversely solve the parameter of the electro-optical conversion function based on the photoelectric conversion function), or may be each image
  • the parameters of the photoelectric conversion function of the code block corresponding to the block (at this time, the decoding end needs to determine the parameter of the inverse function based on the parameters of the photoelectric conversion function).
  • the statistical information may also be a combination of the above information.
  • the photoelectric conversion information of a part of the image block is statistical information obtained by the encoding end
  • the photoelectric conversion information of the other partial image block is an index of the electro-optical conversion function corresponding to the image block.
  • the plurality of electro-optical conversion functions at the decoding end may be inverse functions of a plurality of photoelectric conversion functions at the encoding end. Taking the photoelectric conversion function of the encoding end as the six functions shown in FIG. 3 as an example, the electro-optical conversion function at the decoding end may be the six functions shown in FIG. 5.
  • the spatial locality of the image is fully considered, and the effect of HDR video coding can be improved.
  • the photoelectric conversion information includes index information for indicating an index of an electro-optical conversion function of each image block, wherein the index information is determined by an encoding end based on an index of a photoelectric conversion function corresponding to each image block.
  • the electro-optical conversion function corresponding to each image block is determined in a plurality of electro-optical conversion functions.
  • the foregoing photoelectric conversion information may include a statistical value of the brightness of the coding block corresponding to each image block
  • the step 430 may include: according to the statistical value of the brightness of the coding block corresponding to each image block, respectively Determining a function value of a plurality of preset electro-optic conversion functions; selecting an objective function value having a smallest difference from a preset value from function values of the plurality of electro-optical conversion functions; determining an electro-optical conversion function corresponding to the objective function value as each image block Corresponding electro-optic conversion function.
  • the foregoing photoelectric conversion information includes a statistical value of the brightness of the coding block corresponding to each image block
  • the step 430 may include: determining that the statistical value of the brightness of the coding block corresponding to each image block falls.
  • the first numerical interval wherein the first numerical interval is one of a plurality of preset numerical intervals; and the electro-optical conversion corresponding to the first numerical interval is performed according to a one-to-one correspondence between the plurality of numerical intervals and the plurality of electro-optical conversion functions
  • the function determines the electro-optic conversion function corresponding to each image block.
  • the method further includes: performing inverse quantization on the decoded data in units of 8 bits.
  • the foregoing decoding information includes at least one of the following information of each image block: index information indicating an index of an electro-optic conversion function corresponding to each image block; and indicating each image The information of the parameters of the electro-optical conversion function corresponding to the block; and the statistical value of the brightness of the coding block corresponding to each image block.
  • the statistical value is a brightness average value of the pixel points in each image block, a luminance variance of the pixel points in each image block, and a maximum brightness value of the pixel points in each image block, each image block.
  • the photoelectric conversion information includes a statistical value of the brightness of the coding block corresponding to each image block
  • the step 430 may include: coding the block corresponding to the first image block according to any one of the plurality of image blocks. a statistical value of the brightness, determining an electro-optical conversion function corresponding to the first image block; determining a correlation of a brightness between the coding block corresponding to the image block remaining except the first image block and the coding block corresponding to the first image block; Determining the brightness correlation, determining whether the remaining image blocks share the same electro-optic conversion function with the first image block; when determining that the remaining image blocks share the same electro-optical conversion function with the first image block, corresponding to the first image block
  • the electro-optic conversion function is determined as a global electro-optical conversion function corresponding to the HDR image frame; when it is determined that there are image blocks in the remaining image block that cannot share the same electro-optic conversion function with the first image block, the brightness of the coding block corresponding to
  • the photoelectric conversion information includes a statistical value of the brightness of the coding block corresponding to each image block
  • the step 430 may include: coding the block corresponding to the first image block according to any one of the plurality of image blocks. a statistical value of the brightness, determining an electro-optical conversion function corresponding to the first image block; determining a correlation of a brightness between the coding block corresponding to the image block remaining except the first image block and the coding block corresponding to the first image block; Determining the correlation of the brightness, determining a photoelectric conversion function of the target image block in the remaining image block as an electro-optical conversion function corresponding to the first image block, The correlation between the brightness of the coding block corresponding to the target image block and the brightness of the coding block corresponding to the first image block is greater than a preset threshold.
  • the final conversion value can be obtained by simple linear interpolation of O1 and O2 with the distance between the coordinates of the boundary pixel and the boundary as weights.
  • bilinear interpolation can be similarly used.
  • FIG. 6 is a schematic block diagram of a video encoder according to an embodiment of the present invention. It should be understood that the video encoder 600 of FIG. 6 can implement the various steps performed by the video encoder in FIG. 2, and to avoid repetition, it will not be described in detail herein. Video encoder 600 includes:
  • An acquiring unit 610 configured to acquire an HDR image frame to be encoded, where the HDR image frame includes multiple image blocks;
  • a determining unit 620 configured to determine a photoelectric conversion function corresponding to each image block from a preset plurality of photoelectric conversion functions according to a statistical value of brightness of each of the plurality of image blocks;
  • the photoelectric conversion unit 630 is configured to perform photoelectric conversion on each image block according to a photoelectric conversion function corresponding to each image block;
  • the encoding unit 640 is configured to encode the photoelectrically converted plurality of image blocks.
  • the HDR image frame is divided into a plurality of image blocks, and then the photoelectric conversion function corresponding to each image block is selected from a preset plurality of photoelectric conversion functions according to the statistical value of the brightness of each image block.
  • the photoelectric conversion function of an image block is determined based on the brightness of the image block itself, and the photoelectric conversion functions of different image blocks may be the same or different, and a global photoelectric conversion is used with the entire frame image in the prior art.
  • the spatial locality of the image is fully considered, and the effect of HDR video coding can be improved.
  • the determining unit 620 may be specifically configured according to each image block. a statistical value of the brightness, respectively determining a function value of the preset plurality of photoelectric conversion functions; selecting an objective function value having a smallest difference from the preset value from the function values of the plurality of photoelectric conversion functions; and photoelectrically converting the function corresponding to the target function value The photoelectric conversion function corresponding to each image block is determined.
  • the determining unit 620 may be specifically configured to determine a first value interval in which a statistical value of the brightness of each image block falls, wherein the first value interval is in a preset plurality of value intervals. According to the one-to-one correspondence between the plurality of numerical intervals and the plurality of photoelectric conversion functions, the photoelectric conversion function corresponding to the first numerical interval is determined as the photoelectric corresponding to each image block in which the luminance statistical value falls within the first numerical interval. Conversion function.
  • the encoding unit 640 may be specifically configured to quantize the photoelectrically converted plurality of image blocks in units of 8 bits to obtain quantized data of the plurality of image blocks; The quantized data is encoded.
  • the video encoder 600 may further include: a writing unit, configured to write photoelectric conversion information of each image block into the code stream, where the photoelectric conversion information is used by the decoding end to determine each image block.
  • the electro-optic conversion function of the corresponding decoded block may further include: a writing unit, configured to write photoelectric conversion information of each image block into the code stream, where the photoelectric conversion information is used by the decoding end to determine each image block. The electro-optic conversion function of the corresponding decoded block.
  • the photoelectric conversion information includes at least one of the following information of each image block: an index of a photoelectric conversion function corresponding to each image block; a statistical value of brightness of each image block; and each The parameters of the photoelectric conversion function corresponding to the image block.
  • the statistic value is a histogram statistic value of a luminance mean, a luminance variance, a maximum luminance value, a minimum luminance value, or a luminance of a pixel point in each image block.
  • At least two of the plurality of image blocks correspond to the same photoelectric conversion function.
  • the determining unit 620 is specifically configured to determine, according to a statistical value of the brightness of any one of the plurality of image blocks, a photoelectric conversion function corresponding to the first image block; and determine the first image Correlation of brightness between the remaining image blocks outside the block and the first image block; determining, based on the determined brightness correlation, whether the remaining image blocks share the same photoelectric conversion function as the first image block; when determining the remaining When the image block shares the same photoelectric conversion function as the first image block, the photoelectric conversion function corresponding to the first image block is determined as a global photoelectric conversion function corresponding to the HDR image frame; when it is determined that the remaining image block exists and the first image block When the image blocks of the same photoelectric conversion function cannot be shared, the photoelectric conversion functions corresponding to the respective remaining image blocks are determined based on the statistical values of the brightness of the remaining images.
  • FIG. 7 is a schematic block diagram of a video decoder according to an embodiment of the present invention. It should be understood that the Figure 7 Video decoder 700 is capable of implementing the various steps performed by the video decoder in FIG. 4, to avoid repetition, and will not be described in detail herein. Video decoder 700 includes:
  • a decoding unit 710 configured to decode a code stream to reconstruct an HDR image frame, where the HDR image frame includes multiple image blocks;
  • the obtaining unit 720 is configured to obtain photoelectric conversion information of each of the plurality of image blocks from the code stream, where the photoelectric conversion information is determined by the encoding end based on a statistical value of the brightness of the coding block corresponding to each image block, and the photoelectricity Converting information is used by the decoding end to determine an electro-optical conversion function corresponding to each image block;
  • a determining unit 730 configured to determine, according to the photoelectric conversion information of each image block, an electro-optical conversion function corresponding to each image block from a preset plurality of electro-optical conversion functions;
  • the electro-optical conversion unit 740 is configured to perform electro-optical conversion on each image block according to an electro-optical conversion function corresponding to each image block.
  • the spatial locality of the image is fully considered, and the effect of HDR video coding can be improved.
  • the photoelectric conversion information includes index information for indicating an index of an electro-optical conversion function of each image block, wherein the index information is determined by an encoding end based on an index of a photoelectric conversion function corresponding to each image block.
  • the determining unit 730 is specifically configured to determine an electro-optical conversion function corresponding to each image block from a preset plurality of electro-optical conversion functions according to an index of an electro-optical conversion function of each image block.
  • the photoelectric conversion information includes a statistical value of the brightness of the coding block corresponding to each image block
  • the determining unit 730 may be specifically configured to: according to the statistical value of the brightness of the coding block corresponding to each image block, respectively Determining a function value of a plurality of preset electro-optic conversion functions; selecting an objective function value having a smallest difference from a preset value from function values of the plurality of electro-optical conversion functions; determining an electro-optical conversion function corresponding to the objective function value as each image block Corresponding electro-optic conversion function.
  • the photoelectric conversion information includes a statistical value of the brightness of the coding block corresponding to each image block
  • the determining unit 730 may be specifically configured to determine a statistical value of the brightness of the coding block corresponding to each image block.
  • a first numerical interval wherein the first numerical interval is one of a plurality of preset numerical intervals; and the electro-optic corresponding to the first numerical interval is according to a one-to-one correspondence between the plurality of numerical intervals and the plurality of electro-optical conversion functions
  • the conversion function determines the electro-optic conversion function corresponding to each image block.
  • the video decoder 700 may further include an inverse quantization unit for performing inverse quantization on the decoded data in units of 8 bits.
  • the photoelectric conversion information includes a statistical value of the brightness of the coding block corresponding to each image block
  • the determining unit is specifically configured to use the coding block corresponding to the first image block according to any one of the plurality of image blocks.
  • a statistical value of the brightness determining an electro-optical conversion function corresponding to the first image block; determining a correlation of a brightness between the coding block corresponding to the image block remaining except the first image block and the coding block corresponding to the first image block; Determining the brightness correlation, determining whether the remaining image blocks share the same electro-optic conversion function with the first image block; when determining that the remaining image blocks share the same electro-optical conversion function with the first image block, corresponding to the first image block
  • the electro-optic conversion function is determined as a global electro-optical conversion function corresponding to the HDR image frame; when it is determined that there are image blocks in the remaining image block that cannot share the same electro-optic conversion function with the first image block, the brightness of the coding block corresponding to the remaining image is The statistical value determines the electro-optical conversion function corresponding to each of the remaining image blocks.
  • the photoelectric conversion information includes at least one of the following information of each image block: index information for indicating an index of the electro-optic conversion function corresponding to each image block; for indicating each image The information of the parameters of the electro-optical conversion function corresponding to the block; and the statistical value of the brightness of the coding block corresponding to each image block.
  • the statistic value is a histogram statistic value of a luminance mean value, a luminance variance, a maximum luminance value, a minimum luminance value, or a luminance of a pixel point in the coding block corresponding to each image block.
  • FIG. 8 is a schematic block diagram of a video encoder according to an embodiment of the present invention. It should be understood that the video encoder 800 of FIG. 8 is capable of implementing the various steps performed by the video encoder of FIG. 2, to avoid repetition, and will not be described in detail herein. Video encoder 800 includes:
  • a memory 810 configured to store a program
  • a processor 820 configured to execute a program, when the program is executed, the processor 820 is specifically configured to acquire an HDR image frame to be encoded, where the HDR image frame includes a plurality of image blocks; according to the plurality of image blocks a statistical value of the brightness of each image block, determining a photoelectric conversion function corresponding to each image block from a preset plurality of photoelectric conversion functions; photoelectricizing each image block according to a photoelectric conversion function corresponding to each image block Conversion; encoding a plurality of image blocks after photoelectric conversion.
  • the HDR image frame is divided into a plurality of image blocks, and then the photoelectric conversion function corresponding to each image block is selected from a preset plurality of photoelectric conversion functions according to the statistical value of the brightness of each image block.
  • the photoelectric conversion function of an image block is determined based on the brightness of the image block itself, and the photoelectric conversion functions of different image blocks may be the same or different, and a global photoelectric conversion is used with the entire frame image in the prior art.
  • the spatial locality of the image is fully considered, and the effect of HDR video coding can be improved.
  • the processor 820 may be specifically configured to determine, according to a statistical value of the brightness of each image block, a function value of the preset plurality of photoelectric conversion functions; a function value from the plurality of photoelectric conversion functions. The objective function value having the smallest difference from the preset value is selected; and the photoelectric conversion function corresponding to the target function value is determined as the photoelectric conversion function corresponding to each image block.
  • the processor 820 may be specifically configured to determine a first value interval in which a statistical value of the brightness of each image block falls, wherein the first value interval is a preset plurality of value intervals. And determining, according to a one-to-one correspondence between the plurality of numerical intervals and the plurality of photoelectric conversion functions, the photoelectric conversion function corresponding to the first numerical interval is determined as corresponding to each image block in which the luminance statistical value falls within the first numerical interval Photoelectric conversion function.
  • the processor 820 may be specifically configured to quantize the photoelectrically converted plurality of image blocks in units of 8 bits to obtain quantized data of the plurality of image blocks; The quantized data is encoded.
  • the processor 820 is further configured to write photoelectric conversion information of each image block into the code stream, where the photoelectric conversion information is used by the decoding end to determine an electro-optical conversion function of the decoding block corresponding to each image block. .
  • the photoelectric conversion information includes at least one of the following information of each image block: an index of a photoelectric conversion function corresponding to each image block; a statistical value of brightness of each image block; and each The parameters of the photoelectric conversion function corresponding to the image block.
  • the statistic value is a histogram statistic value of a luminance mean, a luminance variance, a maximum luminance value, a minimum luminance value, or a luminance of a pixel point in each image block.
  • At least two of the plurality of image blocks correspond to the same photoelectric conversion function.
  • the processor 820 is specifically configured to determine, according to a statistical value of the brightness of any one of the plurality of image blocks, a photoelectric conversion function corresponding to the first image block; and determine the first image Correlation of brightness between the remaining image blocks outside the block and the first image block; determining, based on the determined brightness correlation, whether the remaining image blocks share the same photoelectric conversion function as the first image block; when determining the remaining When the image block shares the same photoelectric conversion function as the first image block, the photoelectric conversion function corresponding to the first image block is determined as a global photoelectric conversion function corresponding to the HDR image frame; when it is determined that the remaining image block exists and the first image block When the image blocks of the same photoelectric conversion function cannot be shared, the photoelectric conversion functions corresponding to the respective remaining image blocks are determined based on the statistical values of the brightness of the remaining images.
  • Video decoder 900 includes:
  • a memory 910 configured to store a program
  • the processor 920 is configured to execute a program. When the program is executed, the processor 920 is specifically configured to decode a code stream to reconstruct a high dynamic range HDR image frame, where the HDR image frame includes multiple image blocks; Obtaining photoelectric conversion information of each of the plurality of image blocks in the stream, the photoelectric conversion information is determined by the encoding end based on a statistical value of the brightness of the coding block corresponding to each image block, and the photoelectric conversion information is used by the decoding end to determine each Corresponding electro-optical conversion function corresponding to each image block; determining an electro-optical conversion function corresponding to each image block from a preset plurality of electro-optical conversion functions according to photoelectric conversion information of each image block; and electro-optical conversion function corresponding to each image block , each image block is electro-optic converted.
  • the spatial locality of the image is fully considered, and the effect of HDR video coding can be improved.
  • the photoelectric conversion information includes index information for indicating an index of an electro-optical conversion function of each image block, wherein the index information is determined by an encoding end based on an index of a photoelectric conversion function corresponding to each image block.
  • the processor 920 is specifically configured to determine an electro-optical conversion function corresponding to each image block from a preset plurality of electro-optical conversion functions according to an index of an electro-optical conversion function of each image block.
  • the photoelectric conversion information includes a statistical value of the brightness of the coding block corresponding to each image block
  • the processor 920 may be specifically configured to: according to the statistical value of the brightness of the coding block corresponding to each image block, respectively Determining a function value of the plurality of electro-optical conversion functions; selecting an objective function value having a smallest difference from the preset value from the function values of the plurality of electro-optic conversion functions; determining an electro-optical conversion function corresponding to the objective function value as the electro-optic corresponding to each image block Conversion function.
  • the photoelectric conversion information includes a statistical value of the brightness of the coding block corresponding to each image block
  • the processor 920 may be specifically configured to determine a statistical value of the brightness of the coding block corresponding to each image block.
  • a first numerical interval wherein the first numerical interval is one of a plurality of preset numerical intervals; and the electro-optic corresponding to the first numerical interval is according to a one-to-one correspondence between the plurality of numerical intervals and the plurality of electro-optical conversion functions
  • the conversion function determines the electro-optic conversion function corresponding to each image block.
  • the processor 920 may be specifically configured to perform inverse quantization on data in the code stream in units of 8 bits to obtain inverse quantized data of the HDR image frame; According to the determination of the HDR image frame.
  • the photoelectric conversion information includes a statistical value of the brightness of the coding block corresponding to each image block
  • the processor 920 is specifically configured to use the coding block corresponding to the first image block according to any one of the plurality of image blocks.
  • a statistical value of the brightness determining an electro-optical conversion function corresponding to the first image block; determining a correlation of brightness between the coding block corresponding to the image block remaining except the first image block and the coding block corresponding to the first image block; Determining whether the remaining image blocks share the same electro-optic conversion function with the first image block according to the determined brightness correlation; when determining that the remaining image blocks share the same electro-optical conversion function with the first image block, the first image block is Corresponding electro-optical conversion function is determined as a global electro-optical conversion function corresponding to the HDR image frame; when it is determined that there are image blocks in the remaining image block that cannot share the same electro-optic conversion function with the first image block, according to the coding block corresponding to the remaining image The statistical value of the brightness determines the electro-optic conversion function corresponding to each of the remaining image blocks.
  • the photoelectric conversion information includes at least one of the following information of each image block: index information for indicating an index of the electro-optic conversion function corresponding to each image block; for indicating each image The information of the parameters of the electro-optical conversion function corresponding to the block; and the statistical value of the brightness of the coding block corresponding to each image block.
  • the statistic value is a histogram statistic value of a luminance mean value, a luminance variance, a maximum luminance value, a minimum luminance value, or a luminance of a pixel point in the coding block corresponding to each image block.
  • the disclosed systems, devices, and methods may be implemented in other manners.
  • the device embodiments described above are merely illustrative.
  • the division of the unit is only a logical function division.
  • there may be another division manner for example, multiple units or components may be combined or Can be integrated into another system, or some features can be ignored or not executed.
  • the mutual coupling or direct coupling or communication connection shown or discussed may be indirect coupling through some interface, device or unit.
  • a communication connection which may be in electrical, mechanical or other form.
  • the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, may be located in one place, or may be distributed to multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of the embodiment.
  • each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.
  • the functions may be stored in a computer readable storage medium if implemented in the form of a software functional unit and sold or used as a standalone product.
  • the technical solution of the present invention which is essential or contributes to the prior art, or a part of the technical solution, may be embodied in the form of a software product, which is stored in a storage medium, including
  • the instructions are used to cause a computer device (which may be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods described in various embodiments of the present invention.
  • the foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, and the like. .

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Abstract

本发明实施例提供一种视频编解码方法和视频编解码器，该方法包括：获取待编码的HDR图像帧，其中，HDR图像帧包括多个图像块；根据多个图像块中的每个图像块的亮度的统计值，从预设的多个光电转换函数中确定每个图像块对应的光电转换函数；根据每个图像块对应的光电转换函数，对每个图像块进行光电转换；对经光电转换后的多个图像块进行编码。本发明实施例为每个图像块设置一个对应的光电转换函数，可以提高视频编码的效果，并更好地与现有的视频编码框架相适应。

Description

视频编解码方法和视频编解码器 技术领域
本发明实施例涉及视频编解码领域，并且更具体地，涉及一种视频编解码方法和视频编解码器。
背景技术
在很多领域中，动态范围(Dynamic Range)用来表示某个变量最大值与最小值的比率。在数字图像领域中，动态范围表示了图像可显示的范围内的最大亮度值和最小亮度值之间的比率。自然界中的亮度的动态范围相当大，星空下的夜景亮度约为0.001cd/m2，太阳本身亮度高达1,000,000,000cd/m2，这样的动态范围达到1,000,000,000/0.001＝1013数量级。但是，在自然界的场景中，不会同时得到太阳的亮度和星光的亮度，因此，一般而言，自然界(或真实世界)的亮度的动态范围在10-3到106范围内。
在数字图像中，一般情况下，R、G、B各通道分别使用一个字节(8比特)来存储，也就是说，各通道的亮度表示范围是0～255，这里的0～255就是数字图像的动态范围。
由于自然界的动态范围在10-3到106内，远高于数字图像的动态范围，因此，我们可以称自然界的动态范围为高动态范围(High Dynamic Range，HDR)。相对地，普通的数字图像的动态范围为低动态范围(Low Dynamic Range，LDR)。数码相机的成像过程实际上就是自然界的高动态范围到数字图像的低动态范围的映射。这往往是一个非线性的映射过程。
高动态范围图像(HDR Image，HDRI)是一种可以表示高动态范围变化的图像。由于HDR图像需要表示人眼可见亮度范围，HDR图像的每个颜色通道需要比传统图像更多的数据位。例如，HDR图像的像素经常使用16位“half precision”或者32位浮点数表示。
在HDR图像中存储的信息一般为自然界的真实的光照信息，单位为cd/m2，但显示设备支持的最大照度有限，并不能完全反应自然界的真实的光照。既然人们需要通过显示设备来浏览图像，就需要利用光电转换函数(Optical-Electro Transfer Function，OETF)，将HDR图像中存储的光照信息转换成为显示设备可以显示的电信号。光电转换函数最初应用在传统的阴极 射线管(Cathode Ray Tube，CRT)显示设备上，通过光电转换函数可以很好的将光照信息和CRT显示设备的亮度值对应起来，我们这里的光电转换函数可以是从光照信息到显示设备电信号转换函数的一个统称。因此，光电转换函数转换效果的好坏，直接决定了HDR图像在显示设备上的显示效果的好坏。
HDR视频编码一般以HDR图像帧为单位，对HDR视频流中的HDR图像帧依次进行光电转换、色彩空间转换、量化和视频编码等操作。具体而言，首先对输入的HDR图像帧进行光电转换；然后，将转换后的HDR图像帧的RGB信息转换到YCbCr空间；在YCbCr空间对图像的数据信息进行量化；最后基于量化数据进行视频编码。HDR视频解码为上述过程的逆过程，即首先对码流进行解码，得到解码数据，然后将解码数据通过反量化操作，转化为[0,1]的浮点数据；再通过色彩空间转换将YCbCr空间的数据转化到RGB色彩空间；最后通过电光转换函数(Electro-Optical Transfer Function，EOTF)将RGB色彩信息转换到16位或者32位浮点数，以表示真实世界的亮度信息。
ISO标准提出了一种具体的HDR编码方案“ISO/IEC JTC1/SC29/WG11 MPEG2014/N15083”。在该方案中，编码端的光电转换过程，以及使用的光电转换函数PQ_TF的具体形式参见如下公式(1)：
Figure PCTCN2015081066-appb-000001
其中:
Figure PCTCN2015081066-appb-000002
Figure PCTCN2015081066-appb-000003
Figure PCTCN2015081066-appb-000004
Figure PCTCN2015081066-appb-000005
Figure PCTCN2015081066-appb-000006
Figure PCTCN2015081066-appb-000007
该光电转换函数PQ_TF的曲线图如图1所示。相应地，解码端的电光 转换过程，以及使用的电光转换函数inversePQ_FT(PQ_TF的反函数)的具体形式参见如下公式(2)：
Figure PCTCN2015081066-appb-000008
其中：
Figure PCTCN2015081066-appb-000009
Figure PCTCN2015081066-appb-000010
Figure PCTCN2015081066-appb-000011
Figure PCTCN2015081066-appb-000012
Figure PCTCN2015081066-appb-000013
Figure PCTCN2015081066-appb-000014
上述方案中的光电转换函数是一个全局的光电转换函数，即整个HDR图像帧的像素均通过上述光电转换函数进行转换，但不同图像区域(例如前景和背景区域)的亮度信息不同，整帧图像均使用同一光电转换函数未考虑图像的空间局部性，导致HDR视频编码的效果差。
发明内容
本发明实施例提供一种视频编解码方法和视频编解码器，以提高HDR视频编码的效果。
第一方面，提供一种视频编码方法，包括：获取待编码的HDR图像帧，其中，所述HDR图像帧包括多个图像块；根据所述多个图像块中的每个图像块的亮度的统计值，从预设的多个光电转换函数中确定所述每个图像块对应的光电转换函数；根据所述每个图像块对应的光电转换函数，对所述每个图像块进行光电转换；对经光电转换后的所述多个图像块进行编码。
结合第一方面，在第一方面的一种实现方式中，所述根据所述多个图像块中的每个图像块的亮度的统计值，从预设的多个光电转换函数中确定所述每个图像块对应的光电转换函数，包括：根据所述每个图像块的亮度的统计 值，分别确定所述预设的多个光电转换函数的函数值；从所述多个光电转换函数的函数值中选取与预设值差异最小的目标函数值；将所述目标函数值对应的光电转换函数确定为所述每个图像块对应的光电转换函数。
结合第一方面或其上述实现方式的任一种，在第一方面的另一种实现方式中，所述根据所述多个图像块中的每个图像块的亮度的统计值，从预设的多个光电转换函数中确定所述每个图像块对应的光电转换函数，包括：确定所述每个图像块的亮度的统计值所落入的第一数值区间，其中，所述第一数值区间为预设的多个数值区间中的一个；根据所述多个数值区间与所述多个光电转换函数的一一对应关系，将所述第一数值区间对应的光电转换函数确定为所述亮度统计值落入所述第一数值区间内的每个图像块对应的光电转换函数。
结合第一方面或其上述实现方式的任一种，在第一方面的另一种实现方式中，所述对经光电转换后的所述多个图像块进行编码，包括：以8比特为单位，对光电转换后的所述多个图像块进行量化，得到所述多个图像块的量化数据；根据所述多个图像块的量化数据进行编码。
结合第一方面或其上述实现方式的任一种，在第一方面的另一种实现方式中，所述方法还包括：向码流中写入所述每个图像块的光电转换信息，所述光电转换信息用于解码端确定所述每个图像块对应的解码块的电光转换函数。
结合第一方面或其上述实现方式的任一种，在第一方面的另一种实现方式中，所述光电转换信息包括所述每个图像块的以下信息中的至少一种：所述每个图像块对应的光电转换函数的索引；所述每个图像块的亮度的统计值；以及所述每个图像块对应的光电转换函数的参数。
结合第一方面或其上述实现方式的任一种，在第一方面的另一种实现方式中，所述统计值为所述每个图像块内像素点的亮度均值、亮度方差、最大亮度值、最小亮度值或亮度的直方图统计值。
结合第一方面或其上述实现方式的任一种，在第一方面的另一种实现方式中，所述的多个图像块中的至少两个图像块对应同一个光电转换函数。
结合第一方面或其上述实现方式的任一种，在第一方面的另一种实现方式中，所述根据所述多个图像块中的每个图像块的亮度的统计值，从预设的多个光电转换函数中确定所述每个图像块对应的光电转换函数包括：根据所 述多个图像块中的任意一个第一图像块的亮度的统计值，确定所述第一图像块对应的光电转换函数；确定除所述第一图像块之外剩余的图像块与所述第一图像块之间的亮度的相关性；根据所确定的亮度相关性，确定所述剩余的图像块是否与所述第一图像块共用相同的光电转换函数；当确定所述剩余的图像块与所述第一图像块共用相同的光电转换函数时，将所述第一图像块对应的光电转换函数确定为所述HDR图像帧对应的全局光电转换函数；当确定所述剩余的图像块中存在与所述第一图像块不能共用相同光电转换函数的图像块时，根据所述剩余的图像的亮度的统计值，确定所述剩余图像块各自对应的光电转换函数。
第二方面，提供一种视频解码方法，包括：解码码流以重建高动态范围HDR图像帧，所述HDR图像帧包括多个图像块；从所述码流中获取多个图像块中的每个图像块的光电转换信息，所述光电转换信息由编码端基于所述每个图像块对应的编码块的亮度的统计值确定，且所述光电转换信息用于解码端确定所述每个图像块对应的电光转换函数；根据所述每个图像块的光电转换信息，从预设的多个电光转换函数中确定所述每个图像块对应的电光转换函数；根据所述每个图像块对应的电光转换函数，对所述每个图像块进行电光转换。
结合第二方面，在第二方面的一种实现方式中，所述光电转换信息包括用于指示所述每个图像块的电光转换函数的索引的索引信息，其中，所述索引信息是所述编码端基于所述每个图像块对应的光电转换函数的索引确定的，所述根据所述每个图像块的光电转换信息，从预设的多个电光转换函数中确定所述每个图像块对应的电光转换函数，包括：根据所述每个图像块的电光转换函数的索引，从所述预设的多个电光转换函数中确定所述每个图像块对应的电光转换函数。
结合第二方面或其上述实现方式的任一种，在第二方面的另一种实现方式中，所述光电转换信息包括所述每个图像块对应的编码块的亮度的统计值，所述根据所述每个图像块的光电转换信息，从预设的多个电光转换函数中确定所述每个图像块对应的电光转换函数，包括：根据所述每个图像块对应的编码块的亮度的统计值，分别确定所述预设的多个电光转换函数的函数值；从所述多个电光转换函数的函数值中选取与预设值差异最小的目标函数值；将所述目标函数值对应的电光转换函数确定为所述每个图像块对应的电光 转换函数。
结合第二方面或其上述实现方式的任一种，在第二方面的另一种实现方式中，所述光电转换信息包括所述每个图像块对应的编码块的亮度的统计值，所述根据所述每个图像块的光电转换信息，从预设的多个电光转换函数中确定所述每个图像块对应的电光转换函数，包括：确定所述每个图像块对应的编码块的亮度的统计值所落入的第一数值区间，其中，所述第一数值区间为预设的多个数值区间中的一个；根据所述多个数值区间与所述多个电光转换函数的一一对应关系，将所述第一数值区间对应的电光转换函数确定为所述每个图像块对应的电光转换函数。
结合第二方面或其上述实现方式的任一种，在第二方面的另一种实现方式中，所述光电转换信息包括所述每个图像块对应的编码块的亮度的统计值，所述根据所述每个图像块的光电转换信息，从预设的多个电光转换函数中确定所述每个图像块对应的电光转换函数，包括：根据所述多个图像块中的任意一个第一图像块对应的编码块的亮度的统计值，确定所述第一图像块对应的电光转换函数；确定除所述第一图像块之外剩余的图像块对应的编码块与所述第一图像块对应的编码块之间的亮度的相关性；根据所确定的亮度相关性，确定所述剩余的图像块是否与所述第一图像块共用相同的电光转换函数；当确定所述剩余的图像块与所述第一图像块共用相同的电光转换函数时，将所述第一图像块对应的电光转换函数确定为所述HDR图像帧对应的全局电光转换函数；当确定所述剩余的图像块中存在与所述第一图像块不能共用相同电光转换函数的图像块时，根据所述剩余的图像对应的编码块的亮度的统计值，确定所述剩余图像块各自对应的电光转换函数。
结合第二方面或其上述实现方式的任一种，在第二方面的另一种实现方式中，所述光电转换信息包括所述每个图像块的以下信息中的至少一种：用于指示所述每个图像块对应的电光转换函数的索引的索引信息；用于指示所述每个图像块对应的电光转换函数的参数的信息；以及所述每个图像块对应的编码块的亮度的统计值。
结合第二方面或其上述实现方式的任一种，在第二方面的另一种实现方式中，所述统计值为所述每个图像块对应的编码块内像素点的亮度均值、亮度方差、最大亮度值、最小亮度值或亮度的直方图统计值。
第三方面，提供一种视频编码器，包括：获取单元，用于获取待编码的 HDR图像帧，其中，所述HDR图像帧包括多个图像块；确定单元，用于根据所述多个图像块中的每个图像块的亮度的统计值，从预设的多个光电转换函数中确定所述每个图像块对应的光电转换函数；光电转换单元，用于根据所述每个图像块对应的光电转换函数，对所述每个图像块进行光电转换；编码单元，用于对经光电转换后的所述多个图像块进行编码。
结合第三方面，在第三方面的一种实现方式中，所述确定单元具体用于根据所述每个图像块的亮度的统计值，分别确定所述预设的多个光电转换函数的函数值；从所述多个光电转换函数的函数值中选取与预设值差异最小的目标函数值；将所述目标函数值对应的光电转换函数确定为所述每个图像块对应的光电转换函数。
结合第三方面或其上述实现方式的任一种，在第三方面的另一种实现方式中，所述确定单元具体用于确定所述每个图像块的亮度的统计值所落入的第一数值区间，其中，所述第一数值区间为预设的多个数值区间中的一个；根据所述多个数值区间与所述多个光电转换函数的一一对应关系，将所述第一数值区间对应的光电转换函数确定为所述亮度统计值落入所述第一数值区间内的每个图像块对应的光电转换函数。
结合第三方面或其上述实现方式的任一种，在第三方面的另一种实现方式中，所述编码单元具体用于以8比特为单位，对经光电转换后的所述多个图像块进行量化，得到所述多个图像块的量化数据；根据所述多个图像块的量化数据进行编码。
结合第三方面或其上述实现方式的任一种，在第三方面的另一种实现方式中，所述视频编码器还包括：写入单元，用于向码流中写入所述每个图像块的光电转换信息，所述光电转换信息用于解码端确定所述每个图像块对应的解码块的电光转换函数。
结合第三方面或其上述实现方式的任一种，在第三方面的另一种实现方式中，所述光电转换信息包括所述每个图像块的以下信息中的至少一种：所述每个图像块对应的光电转换函数的索引；所述每个图像块的亮度的统计值；以及所述每个图像块对应的光电转换函数的参数。
结合第三方面或其上述实现方式的任一种，在第三方面的另一种实现方式中，所述统计值为所述每个图像块内像素点的亮度均值、亮度方差、最大亮度值、最小亮度值或亮度的直方图统计值。
结合第三方面或其上述实现方式的任一种，在第三方面的另一种实现方式中，所述的多个图像块中的至少两个图像块对应同一个光电转换函数。
结合第三方面或其上述实现方式的任一种，在第三方面的另一种实现方式中，所述确定单元具体用于根据所述多个图像块中的任意一个第一图像块的亮度的统计值，确定所述第一图像块对应的光电转换函数；确定除所述第一图像块之外剩余的图像块与所述第一图像块之间的亮度的相关性；根据所确定的亮度相关性，确定所述剩余的图像块是否与所述第一图像块共用相同的光电转换函数；当确定所述剩余的图像块与所述第一图像块共用相同的光电转换函数时，将所述第一图像块对应的光电转换函数确定为所述HDR图像帧对应的全局光电转换函数；当确定所述剩余的图像块中存在与所述第一图像块不能共用相同光电转换函数的图像块时，根据所述剩余的图像的亮度的统计值，确定所述剩余图像块各自对应的光电转换函数。
第四方面，提供一种视频解码器，包括：解码单元，用于解码码流以重建高动态范围HDR图像帧，所述HDR图像帧包括多个图像块；获取单元，用于从所述码流中获取多个图像块中的每个图像块的光电转换信息，所述光电转换信息由编码端基于所述每个图像块对应的编码块的亮度的统计值确定，且所述光电转换信息用于解码端确定所述每个图像块对应的电光转换函数；确定单元，用于根据所述每个图像块的光电转换信息，从预设的多个电光转换函数中确定所述每个图像块对应的电光转换函数；电光转换单元，用于根据所述每个图像块对应的电光转换函数，对所述每个图像块进行电光转换。
结合第四方面，在第四方面的一种实现方式中，所述光电转换信息包括用于指示所述每个图像块的电光转换函数的索引的索引信息，其中，所述索引信息是所述编码端基于所述每个图像块对应的光电转换函数的索引确定的，所述确定单元具体用于根据所述每个图像块的电光转换函数的索引，从所述预设的多个电光转换函数中确定所述每个图像块对应的电光转换函数。
结合第四方面或其上述实现方式的任一种，在第四方面的另一种实现方式中，所述光电转换信息包括所述每个图像块对应的编码块的亮度的统计值，所述确定单元具体用于根据所述每个图像块对应的编码块的亮度的统计值，分别确定所述预设的多个电光转换函数的函数值；从所述多个电光转换函数的函数值中选取与预设值差异最小的目标函数值；将所述目标函数值对应的 电光转换函数确定为所述每个图像块对应的电光转换函数。
结合第四方面或其上述实现方式的任一种，在第四方面的另一种实现方式中，所述光电转换信息包括所述每个图像块对应的编码块的亮度的统计值，所述确定单元具体用于确定所述每个图像块对应的编码块的亮度的统计值所落入的第一数值区间，其中，所述第一数值区间为预设的多个数值区间中的一个；根据所述多个数值区间与所述多个电光转换函数的一一对应关系，将所述第一数值区间对应的电光转换函数确定为所述每个图像块对应的电光转换函数。
结合第四方面或其上述实现方式的任一种，在第四方面的另一种实现方式中，所述光电转换信息包括所述每个图像块对应的编码块的亮度的统计值，所述确定单元具体用于根据所述多个图像块中的任意一个第一图像块对应的编码块的亮度的统计值，确定所述第一图像块对应的电光转换函数；确定除所述第一图像块之外剩余的图像块对应的编码块与所述第一图像块对应的编码块之间的亮度的相关性；根据所确定的亮度相关性，确定所述剩余的图像块是否与所述第一图像块共用相同的电光转换函数；当确定所述剩余的图像块与所述第一图像块共用相同的电光转换函数时，将所述第一图像块对应的电光转换函数确定为所述HDR图像帧对应的全局电光转换函数；当确定所述剩余的图像块中存在与所述第一图像块不能共用相同电光转换函数的图像块时，根据所述剩余的图像对应的编码块的亮度的统计值，确定所述剩余图像块各自对应的电光转换函数。
结合第四方面或其上述实现方式的任一种，在第四方面的另一种实现方式中，所述光电转换信息包括所述每个图像块的以下信息中的至少一种：用于指示所述每个图像块对应的电光转换函数的索引的索引信息；用于指示所述每个图像块对应的电光转换函数的参数的信息；以及所述每个图像块对应的编码块的亮度的统计值。
结合第四方面或其上述实现方式的任一种，在第四方面的另一种实现方式中，所述统计值为所述每个图像块对应的编码块内像素点的亮度均值、亮度方差、最大亮度值、最小亮度值或亮度的直方图统计值。
本发明实施例将HDR图像帧分为多个图像块，然后根据每个图像块的亮度的统计值从预设的多个光电转换函数中选取每个图像块对应的光电转换函数。这样，一个图像块的光电转换函数就是基于该图像块自身的局部亮 度情况而确定的，不同图像块的光电转换函数可以相同，也可以不同，与现有技术中的整帧图像使用一个全局光电转换函数的方式相比，充分考虑了图像的空间局部性，能够改善HDR视频编码的效果。
附图说明
为了更清楚地说明本发明实施例的技术方案，下面将对本发明实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1是现有的光电转换函数的曲线图。
图2是本发明实施例的视频编码方法的示意性流程图。
图3是本发明实施例的预设的多个光电转换函数的曲线图。
图4是本发明实施例的视频解码方法的示意性流程图。
图5是本发明实施例的预设的多个电光转换函数的曲线图。
图6是本发明实施例的一种视频编码器的示意性框图。
图7是本发明实施例的一种视频解码器的示意性框图。
图8是本发明实施例的一种视频编码器的示意性框图。
图9是本发明实施例的一种视频解码器的示意性框图。
具体实施方式
下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本发明的一部分实施例，而不是全部实施例。基于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动的前提下所获得的所有其他实施例，都应属于本发明保护的范围。
图2是本发明实施例的视频编码方法的示意性流程图。图2的方法可以由视频编码器执行。图2的方法包括：
210、获取待编码的HDR图像帧，其中，HDR图像帧包括多个图像块。
应理解，上述HDR图像帧可以是从HDR视频流中获取的任意图像帧。该HDR图像帧中的像素的每个颜色分量(或称通道)可以是16位或者32位的浮点数，以表示真实世界的亮度信息。HDR图像帧中的像素可以用RGB表示，单位可以是cd/m2。
220、根据多个图像块中的每个图像块的亮度的统计值，从预设的多个光电转换函数中确定每个图像块对应的光电转换函数。
应理解，上述统计值可以为每个图像块内像素点的亮度均值，每个图像块内像素点的亮度方差，每个图像块内像素点的最大亮度值，每个图像块内像素点的最小亮度值，或者每个图像块内像素点的亮度的直方图统计值。具体地，HDR图像的亮度分量比色度分量更为重要，亮度分量更能反映该场景局部以及整体的照度特性，在编码侧，本发明实施例可以首先对HDR图像帧的每个图像块的亮度进行统计分析，得到每个图像块的亮度的统计值。
应理解，现有技术中存在很多符合人眼特性的光电转换函数，例如上文中的公式(1)就是其中一个。本发明实施例中的预设的多个光电转换函数可以从现有技术中的光电转换函数中选取，也可以通过调节现有技术中的某个光电转换函数的参数的取值而获得。举例说明，可以调节公式(1)中的指数m2的取值，分别给m2赋值48.8，78.8，128.8，168.8，208.8，258.8，得到如图3所示的6个光电转换函数。m2取值越大，曲线的前部就越平缓。
230、根据每个图像块对应的光电转换函数，对每个图像块进行光电转换。
需要说明的是，选定光电转换函数后，具体的光电转换操作就可以按照现有技术的方式进行，如建立查找表，采用分段线性拟合等方式都可以完成光电转换，此处不再赘述。
240、对经光电转换后的多个图像块进行编码。
步骤240可包括：将光电转换后的多个图像块从当前颜色空间(如RGB空间或YUV空间)转换到YCbCr空间；在YCbCr空间，以8比特或10比特为单位对多个图像块的数据信息进行量化，使用量化后的数据进行编码。
本发明实施例中，根据每个图像块的亮度的统计值从预设的多个光电转换函数中选取每个图像块对应的光电转换函数。这样，一个图像块的光电转换函数就是基于该图像块自身的亮度情况而确定的，不同图像块的光电转换函数可以相同，也可以不同，与现有技术中的整帧图像使用一个全局光电转换函数的方式相比，充分考虑了图像的空间局部性，能够改善HDR视频编码的效果。此外，现有的视频图像编码框架一般都是将图像划分成块而进行的，本发明实施例为每个图像块设置一个对应的光电转换函数，可以更好地与现有的视频编码框架相适应。
可选地，作为一个实施例，步骤220可包括：根据每个图像块的亮度的统计值，分别确定预设的多个光电转换函数的函数值；从多个光电转换函数的函数值中选取与预设值差异最小的目标函数值；将目标函数值对应的光电转换函数确定为每个图像块对应的光电转换函数。
例如，由于人眼细节的感受与图像的亮度均值成正比，上述亮度的统计值可以选取每个图像块的亮度均值。以图3所示的6个光电转换函数为例，实际计算时，可以先将亮度均值进行归一化，然后将亮度均值代入图3所示的6个光电转换函数中，得到6个函数值。上述预设值可以设定为0.8，即函数值与0.8最接近的光电转换函数可视为最佳的光电转换函数。这样，通过比较6个函数值与0.8的大小关系，可以选出最佳的光电转换函数，作为每个图像块对应的光电转换函数。
可选地，作为一个实施例，步骤220可包括：确定每个图像块的亮度的统计值所落入的第一数值区间，其中，第一数值区间为预设的多个数值区间中的一个；根据多个数值区间与多个光电转换函数的一一对应关系，将第一数值区间对应的光电转换函数确定为亮度统计值落入第一数值区间内的每个图像块对应的光电转换函数。
参见图1，在ISO标准的HDR编码方案“ISO/IEC JTC1/SC29/WG11 MPEG2014/N15083”中，光电转换函数将[0-0.1]区间(相当于亮度在0-1000cd/m2)的数据映射到0-0.7区间，对于(0.1-1]区间的数据仅能映射至0.7-1这样一个小区间，这样会造成较大量的信息丢失，例如亮度范围在2023-2050cd/m2这样的数据均可能被映射至0.8，丢失了图像在这一亮度范围内的细节信息。为了弥补这一损失，该HDR编码方式并未沿用现有框架的以8比特为单位进行量化的方式，而是将量化的比特数扩充至10比特，这样做一定程度上缓解减少了数据的损失，但却增加了编码的复杂度，造成了资源的浪费，而且与现有的编码框架不兼容。
可选地，作为一个实施例，步骤240可包括：以8比特为单位，对经光电转换后的多个图像块进行量化，得到该多个图像块的量化数据；根据该多个图像块的量化数据进行编码。
应理解，以8比特为单位，对光电转换后的多个图像块进行量化可指：将HDR图像帧中的每个像素点的每个颜色分量量化为8比特大小的数据。
本发明实施例中，由于使用图像块而非整幅图像帧进行光电转换，而图 像块的亮度范围小于整幅图像帧的亮度范围，在这样一个小的亮度范围内，8比特的量化方式可以满足要求，即不会丢失大量图像信息，因此可以继续以8比特为单位进行量化，这样可以更好地与现有的编码框架兼容。
可选地，作为一个实施例，图2的方法还可包括：向码流中写入每个图像块的光电转换信息，光电转换信息用于解码端确定每个图像块对应的解码块的电光转换函数。
可选地，作为一个实施例，上述光电转换信息可包括每个图像块的以下信息中的至少一种：每个图像块对应的光电转换函数的索引；每个图像块的亮度的统计值；以及每个图像块对应的光电转换函数的参数。
例如，在编码端设置有N个光电转化函数，在解码端设置有N个电光转换函数，该N个电光转换函数分别为编码端的N个光电转换函数的逆函数。进一步地，编码端中的N个光电转换函数具有索引，解码端中的N个电光转换函数也具有索引，且互为逆函数的光电转换函数和电光转换函数的索引相同。实际编码时，当确定某个图像块对应的光电转换函数之后，就可以将该光电转换函数的索引写入码流，传到解码端。解码端解码到该图像块对应的解码块时，就可以根据该索引找到对应的电光转换函数。
可选地，作为一个实施例，上述多个图像块中的至少两个图像块对应同一个光电转换函数。
可选地，作为一个实施例，步骤220可包括：根据多个图像块中的任意一个第一图像块的亮度的统计值，确定第一图像块对应的光电转换函数；确定除第一图像块之外剩余的图像块与第一图像块之间的亮度的相关性；根据所确定的亮度相关性，确定剩余的图像块是否与第一图像块共用相同的光电转换函数；当确定剩余的图像块与第一图像块共用相同的光电转换函数时，将第一图像块对应的光电转换函数确定为HDR图像帧对应的全局光电转换函数；当确定剩余的图像块中存在与第一图像块不能共用相同光电转换函数的图像块时，根据剩余的图像的亮度的统计值，确定剩余图像块各自对应的光电转换函数。
应理解，上述确定除第一图像块之外剩余的图像块与第一图像块之间的亮度的相关性的方式可以有多种，例如，确定第一图像块与剩余图像块的亮度的统计值的差值，当该差值小于预设阈值时，判定它们相关性强，否则，判定它们相关性弱。上述当确定剩余的图像块与第一图像块共用相同的光电 转换函数时，将第一图像块对应的光电转换函数确定为HDR图像帧对应的全局光电转换函数是指：当剩余图像块均与第一图像块具有较强的相关性时，可以无需为每个图像块指定一个光电转换函数，仅需要像现有技术那样，为整个HDR图像帧指定一个全局光电转换函数即可，这样可以节省编码端的计算量，并降低码流的数据量。上述当确定剩余的图像块中存在与第一图像块不能共用相同光电转换函数的图像块时，根据剩余的图像的亮度的统计值，确定剩余图像块各自对应的光电转换函数是指：当剩余图像块中存在与第一图像块相关性较弱的图像块时，剩余的图像块中的每个图像块就按照与第一图像块相同的方式确定各自对应的光电转换函数。
应理解，相关性强的图像块对应的光电转换函数相同的可能性较高，相关性弱的图像块对应的光电转换函数相同的可能性较低。本发明实施例正是基于这一点，通过判断图像块之间的相关性来选择是使用全局光电转换函数，还是为每个图像块分配各自的光电转换函数，使得编码端的编码方式更加灵活。
可选地，作为一个实施例，步骤220可包括：根据多个图像块中的任意一个第一图像块的亮度的统计值，确定第一图像块对应的光电转换函数；确定除第一图像块之外剩余的图像块与第一图像块之间的亮度的相关性；根据确定出的亮度的相关性，将所述剩余图像块中的目标图像块的光电转换函数确定为所述第一图像块对应的光电转换函数，其中，所述目标图像块与所述第一图像块的相关性大于预设阈值。
本发明实施例中，方便地得到了与第一图像块相关性强的图像块的光电转换函数，降低了编码端的计算复杂度。
上文中结合图2，从编码端的角度详细描述了根据本发明实施例的视频编码方法，下面将结合图3，从解码端的角度描述根据本发明实施例的视频解码方法。
应理解，编码端与解码端的功能、操作以及特性相应，为了简洁，适当省略重复的描述。
图4是本发明实施例的视频解码方法的示意性流程图。图4的方法可以由解码器执行。图4的方法包括：
410、解码码流以重建HDR图像帧，HDR图像帧包括多个图像块。
420、从码流中获取多个图像块中的每个图像块的光电转换信息，光电 转换信息由编码端基于每个图像块对应的编码块的亮度的统计值确定，且光电转换信息用于解码端确定每个图像块对应的电光转换函数。
应理解，在解码端，需要利用编码端传来的光电转换信息确定每个图像块对应的电光转换函数，上述光电转换信息可以是编码端得到的亮度统计信息的部分或全部，也可以是每个图像块对应的电光转换函数的索引，还可以是每个图像块对应的电光转换函数的参数(需要编码端基于光电转换函数反解出该电光转换函数的参数)，还可以是每个图像块对应的编码块的光电转换函数的参数(此时解码端需要基于该光电转换函数的参数确定其逆函数的参数)。当然，统计信息还可以是以上信息的组合，例如，一部分图像块的光电转换信息为编码端得到的统计信息，另一部分图像块的光电转换信息为这些图像块对应的电光转换函数的索引。
430、根据每个图像块的光电转换信息，从预设的多个电光转换函数中确定每个图像块对应的电光转换函数。
应理解，解码端的多个电光转换函数可以是编码端的多个光电转换函数的逆函数。以编码端的光电转换函数为图3所示的6个函数为例，解码端的电光转换函数可以是图5所示的6个函数。
440、根据每个图像块对应的电光转换函数，对每个图像块进行电光转换。
本发明实例中，通过确定每个图像块对应的电光转换函数，充分考虑了图像的空间局部性，能够改善HDR视频编码的效果。
可选地，作为一个实施例，光电转换信息包括用于指示每个图像块的电光转换函数的索引的索引信息，其中，索引信息是编码端基于每个图像块对应的光电转换函数的索引确定的，根据每个图像块的光电转换信息，从预设的多个电光转换函数中确定每个图像块对应的电光转换函数，包括：根据每个图像块的电光转换函数的索引，从预设的多个电光转换函数中确定每个图像块对应的电光转换函数。
可选地，作为一个实施例，上述光电转换信息可包括每个图像块对应的编码块的亮度的统计值，步骤430可包括：根据每个图像块对应的编码块的亮度的统计值，分别确定预设的多个电光转换函数的函数值；从多个电光转换函数的函数值中选取与预设值差异最小的目标函数值；将目标函数值对应的电光转换函数确定为每个图像块对应的电光转换函数。
可选地，作为一个实施例，上述光电转换信息包括每个图像块对应的编码块的亮度的统计值，步骤430可包括：确定每个图像块对应的编码块的亮度的统计值所落入的第一数值区间，其中，第一数值区间为预设的多个数值区间中的一个；根据多个数值区间与多个电光转换函数的一一对应关系，将第一数值区间对应的电光转换函数确定为每个图像块对应的电光转换函数。
可选地，作为一个实施例，在步骤410之后还可包括：以8比特为单位，对解码数据进行反量化。
可选地，作为一个实施例，上述解码信息包括每个图像块的以下信息中的至少一种：用于指示每个图像块对应的电光转换函数的索引的索引信息；用于指示每个图像块对应的电光转换函数的参数的信息；以及每个图像块对应的编码块的亮度的统计值。
可选地，作为一个实施例，统计值为每个图像块内像素点的亮度均值，每个图像块内像素点的亮度方差，每个图像块内像素点的最大亮度值，每个图像块内像素点的最小亮度值，或者每个图像块内像素点的亮度的直方图统计值。
可选地，作为一个实施例，光电转换信息包括每个图像块对应的编码块的亮度的统计值，步骤430可包括：根据多个图像块中的任意一个第一图像块对应的编码块的亮度的统计值，确定第一图像块对应的电光转换函数；确定除第一图像块之外剩余的图像块对应的编码块与第一图像块对应的编码块之间的亮度的相关性；根据所确定的亮度相关性，确定剩余的图像块是否与第一图像块共用相同的电光转换函数；当确定剩余的图像块与第一图像块共用相同的电光转换函数时，将第一图像块对应的电光转换函数确定为HDR图像帧对应的全局电光转换函数；当确定剩余的图像块中存在与第一图像块不能共用相同电光转换函数的图像块时，根据剩余的图像对应的编码块的亮度的统计值，确定剩余图像块各自对应的电光转换函数。
可选地，作为一个实施例，光电转换信息包括每个图像块对应的编码块的亮度的统计值，步骤430可包括：根据多个图像块中的任意一个第一图像块对应的编码块的亮度的统计值，确定第一图像块对应的电光转换函数；确定除第一图像块之外剩余的图像块对应的编码块与第一图像块对应的编码块之间的亮度的相关性；根据确定出的亮度的相关性，将所述剩余图像块中目标图像块的光电转换函数确定为所述第一图像块对应的电光转换函数，其 中，所述目标图像块对应的编码块的亮度与所述第一图像块对应的编码块的亮度的相关性大于预设阈值。
对于绝大部分场景，直接的光电转换和电光转换都能很好的恢复HDR图像。然而，对于部分极端HDR场景，如动态范围非常大或者特殊测试场景，可能会由于相邻图像块采用不一样的转换函数而出现轻微的块效应。对于此类问题，有效的解决方法是对于块边界的像素(假设为4)采用混合处理：首先，用本图像块的转换函数以及相邻块的转换函数分别通过计算或者查找表的方式得到边界像素的转换值O1及O2。然后，为确保局部的方法在块边界像素不会出现块效应，可以以边界像素的坐标与边界的距离为权重对O1及O2进行简单线性插值得到最终的转换值。对于四角的边界像素，可以类似的采用双线性插值。解决图像块的块效应的方式很多，具体可以参照现有技术，此处不再详述。
上文中结合图1至图5，详细描述了根据本发明实施例的视频编码方法，下面将结合图6至图9，详细描述根据本发明实施例的视频编解码器。
图6是本发明实施例的一种视频编码器的示意性框图。应理解，图6的视频编码器600能够实现图2中的由视频编码器执行的各个步骤，为避免重复，此处不再详述。视频编码器600包括：
获取单元610，用于获取待编码的HDR图像帧，其中，HDR图像帧包括多个图像块；
确定单元620，用于根据多个图像块中的每个图像块的亮度的统计值，从预设的多个光电转换函数中确定每个图像块对应的光电转换函数；
光电转换单元630，用于根据每个图像块对应的光电转换函数，对每个图像块进行光电转换；
编码单元640，用于对经光电转换后的多个图像块进行编码。
本发明实施例将HDR图像帧分为多个图像块，然后根据每个图像块的亮度的统计值从预设的多个光电转换函数中选取每个图像块对应的光电转换函数。这样，一个图像块的光电转换函数就是基于该图像块自身的亮度情况而确定的，不同图像块的光电转换函数可以相同，也可以不同，与现有技术中的整帧图像使用一个全局光电转换函数的方式相比，充分考虑了图像的空间局部性，能够改善HDR视频编码的效果。
可选地，作为一个实施例，确定单元620可具体用于根据每个图像块的 亮度的统计值，分别确定预设的多个光电转换函数的函数值；从多个光电转换函数的函数值中选取与预设值差异最小的目标函数值；将目标函数值对应的光电转换函数确定为每个图像块对应的光电转换函数。
可选地，作为一个实施例，确定单元620可具体用于确定每个图像块的亮度的统计值所落入的第一数值区间，其中，第一数值区间为预设的多个数值区间中的一个；根据多个数值区间与多个光电转换函数的一一对应关系，将第一数值区间对应的光电转换函数确定为亮度统计值落入第一数值区间内的每个图像块对应的光电转换函数。
可选地，作为一个实施例，编码单元640可具体用于以8比特为单位，对经光电转换后的多个图像块进行量化，得到多个图像块的量化数据；根据多个图像块的量化数据进行编码。
可选地，作为一个实施例，视频编码器600还可包括：写入单元，用于向码流中写入每个图像块的光电转换信息，光电转换信息用于解码端确定每个图像块对应的解码块的电光转换函数。
可选地，作为一个实施例，光电转换信息包括每个图像块的以下信息中的至少一种：每个图像块对应的光电转换函数的索引；每个图像块的亮度的统计值；以及每个图像块对应的光电转换函数的参数。
可选地，作为一个实施例，统计值为每个图像块内像素点的亮度均值、亮度方差、最大亮度值、最小亮度值或亮度的直方图统计值。
可选地，作为一个实施例，多个图像块中的至少两个图像块对应同一个光电转换函数。
可选地，作为一个实施例，确定单元620具体用于根据多个图像块中的任意一个第一图像块的亮度的统计值，确定第一图像块对应的光电转换函数；确定除第一图像块之外剩余的图像块与第一图像块之间的亮度的相关性；根据所确定的亮度相关性，确定剩余的图像块是否与第一图像块共用相同的光电转换函数；当确定剩余的图像块与第一图像块共用相同的光电转换函数时，将第一图像块对应的光电转换函数确定为HDR图像帧对应的全局光电转换函数；当确定剩余的图像块中存在与第一图像块不能共用相同光电转换函数的图像块时，根据剩余的图像的亮度的统计值，确定剩余图像块各自对应的光电转换函数。
图7是本发明实施例的一种视频解码器的示意性框图。应理解，图7的 视频解码器700能够实现图4中由视频解码器执行的各个步骤，为避免重复，此处不再详述。视频解码器700包括：
解码单元710，用于解码码流以重建HDR图像帧，HDR图像帧包括多个图像块；
获取单元720，用于从码流中获取多个图像块中的每个图像块的光电转换信息，光电转换信息由编码端基于每个图像块对应的编码块的亮度的统计值确定，且光电转换信息用于解码端确定每个图像块对应的电光转换函数；
确定单元730，用于根据每个图像块的光电转换信息，从预设的多个电光转换函数中确定每个图像块对应的电光转换函数；
电光转换单元740，用于根据每个图像块对应的电光转换函数，对每个图像块进行电光转换。
本发明实例中，通过确定每个图像块对应的电光转换函数，充分考虑了图像的空间局部性，能够改善HDR视频编码的效果。
可选地，作为一个实施例，光电转换信息包括用于指示每个图像块的电光转换函数的索引的索引信息，其中，索引信息是编码端基于每个图像块对应的光电转换函数的索引确定的，确定单元730可具体用于根据每个图像块的电光转换函数的索引，从预设的多个电光转换函数中确定每个图像块对应的电光转换函数。
可选地，作为一个实施例，光电转换信息包括每个图像块对应的编码块的亮度的统计值，确定单元730可具体用于根据每个图像块对应的编码块的亮度的统计值，分别确定预设的多个电光转换函数的函数值；从多个电光转换函数的函数值中选取与预设值差异最小的目标函数值；将目标函数值对应的电光转换函数确定为每个图像块对应的电光转换函数。
可选地，作为一个实施例，光电转换信息包括每个图像块对应的编码块的亮度的统计值，确定单元730可具体用于确定每个图像块对应的编码块的亮度的统计值所落入的第一数值区间，其中，第一数值区间为预设的多个数值区间中的一个；根据多个数值区间与多个电光转换函数的一一对应关系，将第一数值区间对应的电光转换函数确定为每个图像块对应的电光转换函数。
可选地，作为一个实施例，视频解码器700还可包括反量化单元，用于以8比特为单位，对解码数据进行反量化。
可选地，作为一个实施例，光电转换信息包括每个图像块对应的编码块的亮度的统计值，确定单元具体用于根据多个图像块中的任意一个第一图像块对应的编码块的亮度的统计值，确定第一图像块对应的电光转换函数；确定除第一图像块之外剩余的图像块对应的编码块与第一图像块对应的编码块之间的亮度的相关性；根据所确定的亮度相关性，确定剩余的图像块是否与第一图像块共用相同的电光转换函数；当确定剩余的图像块与第一图像块共用相同的电光转换函数时，将第一图像块对应的电光转换函数确定为HDR图像帧对应的全局电光转换函数；当确定剩余的图像块中存在与第一图像块不能共用相同电光转换函数的图像块时，根据剩余的图像对应的编码块的亮度的统计值，确定剩余图像块各自对应的电光转换函数。
可选地，作为一个实施例，光电转换信息包括每个图像块的以下信息中的至少一种：用于指示每个图像块对应的电光转换函数的索引的索引信息；用于指示每个图像块对应的电光转换函数的参数的信息；以及每个图像块对应的编码块的亮度的统计值。
可选地，作为一个实施例，统计值为每个图像块对应的编码块内像素点的亮度均值、亮度方差、最大亮度值、最小亮度值或亮度的直方图统计值。
图8是本发明实施例的一种视频编码器的示意性框图。应理解，图8的视频编码器800能够实现图2中的由视频编码器执行的各个步骤，为避免重复，此处不再详述。视频编码器800包括：
存储器810，用于存储程序；
处理器820，用于执行程序，当所述程序被执行时，所述处理器820具体用于获取待编码的HDR图像帧，其中，HDR图像帧包括多个图像块；根据多个图像块中的每个图像块的亮度的统计值，从预设的多个光电转换函数中确定每个图像块对应的光电转换函数；根据每个图像块对应的光电转换函数，对每个图像块进行光电转换；对经光电转换后的多个图像块进行编码。
本发明实施例将HDR图像帧分为多个图像块，然后根据每个图像块的亮度的统计值从预设的多个光电转换函数中选取每个图像块对应的光电转换函数。这样，一个图像块的光电转换函数就是基于该图像块自身的亮度情况而确定的，不同图像块的光电转换函数可以相同，也可以不同，与现有技术中的整帧图像使用一个全局光电转换函数的方式相比，充分考虑了图像的空间局部性，能够改善HDR视频编码的效果。
可选地，作为一个实施例，处理器820可具体用于根据每个图像块的亮度的统计值，分别确定预设的多个光电转换函数的函数值；从多个光电转换函数的函数值中选取与预设值差异最小的目标函数值；将目标函数值对应的光电转换函数确定为每个图像块对应的光电转换函数。
可选地，作为一个实施例，处理器820可具体用于确定每个图像块的亮度的统计值所落入的第一数值区间，其中，第一数值区间为预设的多个数值区间中的一个；根据多个数值区间与多个光电转换函数的一一对应关系，将第一数值区间对应的光电转换函数确定为亮度统计值落入所述第一数值区间内的每个图像块对应的光电转换函数。
可选地，作为一个实施例，处理器820可具体用于以8比特为单位，对经光电转换后的多个图像块进行量化，得到多个图像块的量化数据；根据多个图像块的量化数据进行编码。
可选地，作为一个实施例，处理器820还用于向码流中写入每个图像块的光电转换信息，光电转换信息用于解码端确定每个图像块对应的解码块的电光转换函数。
可选地，作为一个实施例，光电转换信息包括每个图像块的以下信息中的至少一种：每个图像块对应的光电转换函数的索引；每个图像块的亮度的统计值；以及每个图像块对应的光电转换函数的参数。
可选地，作为一个实施例，统计值为每个图像块内像素点的亮度均值、亮度方差、最大亮度值、最小亮度值或亮度的直方图统计值。
可选地，作为一个实施例，多个图像块中的至少两个图像块对应同一个光电转换函数。
可选地，作为一个实施例，处理器820具体用于根据多个图像块中的任意一个第一图像块的亮度的统计值，确定第一图像块对应的光电转换函数；确定除第一图像块之外剩余的图像块与第一图像块之间的亮度的相关性；根据所确定的亮度相关性，确定剩余的图像块是否与第一图像块共用相同的光电转换函数；当确定剩余的图像块与第一图像块共用相同的光电转换函数时，将第一图像块对应的光电转换函数确定为HDR图像帧对应的全局光电转换函数；当确定剩余的图像块中存在与第一图像块不能共用相同光电转换函数的图像块时，根据剩余的图像的亮度的统计值，确定剩余图像块各自对应的光电转换函数。
图9是本发明实施例的一种视频解码器的示意性框图。应理解，图9的视频解码器900能够实现图4中由视频解码器执行的各个步骤，为避免重复，此处不再详述。视频解码器900包括：
存储器910，用于存储程序；
处理器920，用于执行程序，当所述程序被执行时，所述处理器920具体用于解码码流以重建高动态范围HDR图像帧，所述HDR图像帧包括多个图像块；从码流中获取多个图像块中的每个图像块的光电转换信息，光电转换信息由编码端基于每个图像块对应的编码块的亮度的统计值确定，且光电转换信息用于解码端确定每个图像块对应的电光转换函数；根据每个图像块的光电转换信息，从预设的多个电光转换函数中确定每个图像块对应的电光转换函数；根据每个图像块对应的电光转换函数，对每个图像块进行电光转换。
本发明实例中，通过确定每个图像块对应的电光转换函数，充分考虑了图像的空间局部性，能够改善HDR视频编码的效果。
可选地，作为一个实施例，光电转换信息包括用于指示每个图像块的电光转换函数的索引的索引信息，其中，索引信息是编码端基于每个图像块对应的光电转换函数的索引确定的，处理器920可具体用于根据每个图像块的电光转换函数的索引，从预设的多个电光转换函数中确定每个图像块对应的电光转换函数。
可选地，作为一个实施例，光电转换信息包括每个图像块对应的编码块的亮度的统计值，处理器920可具体用于根据每个图像块对应的编码块的亮度的统计值，分别确定多个电光转换函数的函数值；从多个电光转换函数的函数值中选取与预设值差异最小的目标函数值；将目标函数值对应的电光转换函数确定为每个图像块对应的电光转换函数。
可选地，作为一个实施例，光电转换信息包括每个图像块对应的编码块的亮度的统计值，处理器920可具体用于确定每个图像块对应的编码块的亮度的统计值所落入的第一数值区间，其中，第一数值区间为预设的多个数值区间中的一个；根据多个数值区间与多个电光转换函数的一一对应关系，将第一数值区间对应的电光转换函数确定为每个图像块对应的电光转换函数。
可选地，作为一个实施例，处理器920可具体用于以8比特为单位，对码流中的数据进行反量化，得到HDR图像帧的反量化数据；根据反量化数 据，确定HDR图像帧。
可选地，作为一个实施例，光电转换信息包括每个图像块对应的编码块的亮度的统计值，处理器920具体用于根据多个图像块中的任意一个第一图像块对应的编码块的亮度的统计值，确定第一图像块对应的电光转换函数；确定除第一图像块之外剩余的图像块对应的编码块与第一图像块对应的编码块之间的亮度的相关性；根据所确定的亮度相关性，确定剩余的图像块是否与第一图像块共用相同的电光转换函数；当确定剩余的图像块与第一图像块共用相同的电光转换函数时，将第一图像块对应的电光转换函数确定为HDR图像帧对应的全局电光转换函数；当确定剩余的图像块中存在与第一图像块不能共用相同电光转换函数的图像块时，根据剩余的图像对应的编码块的亮度的统计值，确定剩余图像块各自对应的电光转换函数。
可选地，作为一个实施例，光电转换信息包括每个图像块的以下信息中的至少一种：用于指示每个图像块对应的电光转换函数的索引的索引信息；用于指示每个图像块对应的电光转换函数的参数的信息；以及每个图像块对应的编码块的亮度的统计值。
可选地，作为一个实施例，统计值为每个图像块对应的编码块内像素点的亮度均值、亮度方差、最大亮度值、最小亮度值或亮度的直方图统计值。
本领域普通技术人员可以意识到，结合本文中所公开的实施例描述的各示例的单元及算法步骤，能够以电子硬件、或者计算机软件和电子硬件的结合来实现。这些功能究竟以硬件还是软件方式来执行，取决于技术方案的特定应用和设计约束条件。专业技术人员可以对每个特定的应用来使用不同方法来实现所描述的功能，但是这种实现不应认为超出本发明的范围。
所属领域的技术人员可以清楚地了解到，为描述的方便和简洁，上述描述的系统、装置和单元的具体工作过程，可以参考前述方法实施例中的对应过程，在此不再赘述。
在本申请所提供的几个实施例中，应该理解到，所揭露的系统、装置和方法，可以通过其它的方式实现。例如，以上所描述的装置实施例仅仅是示意性的，例如，所述单元的划分，仅仅为一种逻辑功能划分，实际实现时可以有另外的划分方式，例如多个单元或组件可以结合或者可以集成到另一个系统，或一些特征可以忽略，或不执行。另一点，所显示或讨论的相互之间的耦合或直接耦合或通信连接可以是通过一些接口，装置或单元的间接耦合 或通信连接，可以是电性，机械或其它的形式。
所述作为分离部件说明的单元可以是或者也可以不是物理上分开的，作为单元显示的部件可以是或者也可以不是物理单元，即可以位于一个地方，或者也可以分布到多个网络单元上。可以根据实际的需要选择其中的部分或者全部单元来实现本实施例方案的目的。
另外，在本发明各个实施例中的各功能单元可以集成在一个处理单元中，也可以是各个单元单独物理存在，也可以两个或两个以上单元集成在一个单元中。
所述功能如果以软件功能单元的形式实现并作为独立的产品销售或使用时，可以存储在一个计算机可读取存储介质中。基于这样的理解，本发明的技术方案本质上或者说对现有技术做出贡献的部分或者该技术方案的部分可以以软件产品的形式体现出来，该计算机软件产品存储在一个存储介质中，包括若干指令用以使得一台计算机设备(可以是个人计算机，服务器，或者网络设备等)执行本发明各个实施例所述方法的全部或部分步骤。而前述的存储介质包括：U盘、移动硬盘、只读存储器(ROM，Read-Only Memory)、随机存取存储器(RAM，Random Access Memory)、磁碟或者光盘等各种可以存储程序代码的介质。
以上所述，仅为本发明的具体实施方式，但本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本发明的保护范围之内。因此，本发明的保护范围应所述以权利要求的保护范围为准。

Claims (32)

  1. 一种视频编码方法，其特征在于，包括：
    获取待编码的高动态范围HDR图像帧，其中，所述HDR图像帧包括多个图像块；
    根据所述多个图像块中的每个图像块的亮度的统计值，从预设的多个光电转换函数中确定所述每个图像块对应的光电转换函数；
    根据所述每个图像块对应的光电转换函数，对所述每个图像块进行光电转换；
    对经光电转换后的所述多个图像块进行编码。
  2. 如权利要求1所述的方法，其特征在于，所述根据所述多个图像块中的每个图像块的亮度的统计值，从预设的多个光电转换函数中确定所述每个图像块对应的光电转换函数，包括：
    根据所述每个图像块的亮度的统计值，分别确定所述预设的多个光电转换函数的函数值；
    从所述多个光电转换函数的函数值中选取与预设值差异最小的目标函数值；
    将所述目标函数值对应的光电转换函数确定为所述每个图像块对应的光电转换函数。
  3. 如权利要求1所述的方法，其特征在于，所述根据所述多个图像块中的每个图像块的亮度的统计值，从预设的多个光电转换函数中确定所述每个图像块对应的光电转换函数，包括：
    确定所述每个图像块的亮度的统计值所落入的第一数值区间，其中，所述第一数值区间为预设的多个数值区间中的一个；
    根据所述多个数值区间与所述多个光电转换函数的一一对应关系，将所述第一数值区间对应的光电转换函数确定为所述亮度统计值落入所述第一数值区间内的每个图像块对应的光电转换函数。
  4. 如权利要求1-3中任一项所述的方法，其特征在于，所述对经光电转换后的所述多个图像块进行编码，包括：
    以8比特为单位，对经光电转换后的所述多个图像块进行量化，得到所述多个图像块的量化数据；
    根据所述多个图像块的量化数据进行编码。
  5. 如权利要求1-4中任一项所述的方法，其特征在于，所述方法还包括：
    向码流中写入所述每个图像块的光电转换信息，所述光电转换信息用于解码端确定所述每个图像块对应的解码块的电光转换函数。
  6. 如权利要求5所述的方法，其特征在于，所述光电转换信息包括所述每个图像块的以下信息中的至少一种：
    所述每个图像块对应的光电转换函数的索引；
    所述每个图像块的亮度的统计值；以及
    所述每个图像块对应的光电转换函数的参数。
  7. 如权利要求1-6中任一项所述的方法，其特征在于，所述统计值为所述每个图像块内像素点的亮度均值、亮度方差、最大亮度值、最小亮度值或亮度的直方图统计值。
  8. 如权利要求1-7中任一项所述的方法，其特征在于，所述的多个图像块中的至少两个图像块对应同一个光电转换函数。
  9. 如权利要求1-8中任一项所述的方法，其特征在于，所述根据所述多个图像块中的每个图像块的亮度的统计值，从预设的多个光电转换函数中确定所述每个图像块对应的光电转换函数包括：
    根据所述多个图像块中的任意一个第一图像块的亮度的统计值，确定所述第一图像块对应的光电转换函数；
    确定除所述第一图像块之外剩余的图像块与所述第一图像块之间的亮度的相关性；
    根据所确定的亮度相关性，确定所述剩余的图像块是否与所述第一图像块共用相同的光电转换函数；
    当确定所述剩余的图像块与所述第一图像块共用相同的光电转换函数时，将所述第一图像块对应的光电转换函数确定为所述HDR图像帧对应的全局光电转换函数；
    当确定所述剩余的图像块中存在与所述第一图像块不能共用相同光电转换函数的图像块时，根据所述剩余的图像的亮度的统计值，确定所述剩余图像块各自对应的光电转换函数。
  10. 一种视频解码方法，其特征在于，包括：
    解码码流以重建高动态范围HDR图像帧，所述HDR图像帧包括多个图 像块；
    从所述码流中获取多个图像块中的每个图像块的光电转换信息，所述光电转换信息用于解码端确定所述每个图像块对应的电光转换函数；
    根据所述每个图像块的光电转换信息，从预设的多个电光转换函数中确定所述每个图像块对应的电光转换函数；
    根据所述每个图像块对应的电光转换函数，对所述每个图像块进行电光转换。
  11. 如权利要求10所述的方法，其特征在于，所述光电转换信息包括用于指示所述每个图像块的电光转换函数的索引的索引信息，
    所述根据所述每个图像块的光电转换信息，从预设的多个电光转换函数中确定所述每个图像块对应的电光转换函数，包括：
    根据所述每个图像块的电光转换函数的索引，从所述预设的多个电光转换函数中确定所述每个图像块对应的电光转换函数。
  12. 如权利要求10所述的方法，其特征在于，所述光电转换信息包括所述每个图像块对应的编码块的亮度的统计值，
    所述根据所述每个图像块的光电转换信息，从预设的多个电光转换函数中确定所述每个图像块对应的电光转换函数，包括：
    根据所述每个图像块对应的编码块的亮度的统计值，分别确定所述预设的多个电光转换函数的函数值；
    从所述多个电光转换函数的函数值中选取与预设值差异最小的目标函数值；
    将所述目标函数值对应的电光转换函数确定为所述每个图像块对应的电光转换函数。
  13. 如权利要求10所述的方法，其特征在于，所述光电转换信息包括所述每个图像块对应的编码块的亮度的统计值，
    所述根据所述每个图像块的光电转换信息，从预设的多个电光转换函数中确定所述每个图像块对应的电光转换函数，包括：
    确定所述每个图像块对应的编码块的亮度的统计值所落入的第一数值区间，其中，所述第一数值区间为预设的多个数值区间中的一个；
    根据所述多个数值区间与所述多个电光转换函数的一一对应关系，将所述第一数值区间对应的电光转换函数确定为所述每个图像块对应的电光转 换函数。
  14. 如权利要求10-13中任一项所述的方法，其特征在于，所述光电转换信息包括所述每个图像块对应的编码块的亮度的统计值，
    所述根据所述每个图像块的光电转换信息，从预设的多个电光转换函数中确定所述每个图像块对应的电光转换函数，包括：
    根据所述多个图像块中的任意一个第一图像块对应的编码块的亮度的统计值，确定所述第一图像块对应的电光转换函数；
    确定除所述第一图像块之外剩余的图像块对应的编码块与所述第一图像块对应的编码块之间的亮度的相关性；
    根据所确定的亮度相关性，确定所述剩余的图像块是否与所述第一图像块共用相同的电光转换函数；
    当确定所述剩余的图像块与所述第一图像块共用相同的电光转换函数时，将所述第一图像块对应的电光转换函数确定为所述HDR图像帧对应的全局电光转换函数；
    当确定所述剩余的图像块中存在与所述第一图像块不能共用相同电光转换函数的图像块时，根据所述剩余的图像对应的编码块的亮度的统计值，确定所述剩余图像块各自对应的电光转换函数。
  15. 如权利要求10-14中任一项所述的方法，其特征在于，所述光电转换信息包括所述每个图像块的以下信息中的至少一种：
    用于指示所述每个图像块对应的电光转换函数的索引的索引信息；
    用于指示所述每个图像块对应的电光转换函数的参数的信息；以及
    所述每个图像块对应的编码块的亮度的统计值。
  16. 如权利要求10-15中任一项所述的方法，其特征在于，所述统计值为所述每个图像块对应的编码块内像素点的亮度均值、亮度方差、最大亮度值、最小亮度值或亮度的直方图统计值。
  17. 一种视频编码器，其特征在于，包括：
    获取单元，用于获取待编码的高动态范围HDR图像帧，其中，所述HDR图像帧包括多个图像块；
    确定单元，用于根据所述多个图像块中的每个图像块的亮度的统计值，从预设的多个光电转换函数中确定所述每个图像块对应的光电转换函数；
    光电转换单元，用于根据所述每个图像块对应的光电转换函数，对所述 每个图像块进行光电转换；
    编码单元，用于对经光电转换后的所述多个图像块进行编码。
  18. 如权利要求17所述的视频编码器，其特征在于，所述确定单元具体用于根据所述每个图像块的亮度的统计值，分别确定所述预设的多个光电转换函数的函数值；从所述多个光电转换函数的函数值中选取与预设值差异最小的目标函数值；将所述目标函数值对应的光电转换函数确定为所述每个图像块对应的光电转换函数。
  19. 如权利要求17所述的视频编码器，其特征在于，所述确定单元具体用于确定所述每个图像块的亮度的统计值所落入的第一数值区间，其中，所述第一数值区间为预设的多个数值区间中的一个；根据所述多个数值区间与所述多个光电转换函数的一一对应关系，将所述第一数值区间对应的光电转换函数确定为所述亮度统计值落入所述第一数值区间内的每个图像块对应的光电转换函数。
  20. 如权利要求17-19中任一项所述的视频编码器，其特征在于，所述编码单元具体用于以8比特为单位，对经光电转换后的所述多个图像块进行量化，得到所述多个图像块的量化数据；根据所述多个图像块的量化数据进行编码。
  21. 如权利要求17-20中任一项所述的视频编码器，其特征在于，所述视频编码器还包括：写入单元，用于向码流中写入所述每个图像块的光电转换信息，所述光电转换信息用于解码端确定所述每个图像块对应的解码块的电光转换函数。
  22. 如权利要求21所述的视频编码器，其特征在于，所述光电转换信息包括所述每个图像块的以下信息中的至少一种：
    所述每个图像块对应的光电转换函数的索引；
    所述每个图像块的亮度的统计值；以及
    所述每个图像块对应的光电转换函数的参数。
  23. 如权利要求17-22中任一项所述的视频编码器，其特征在于，所述统计值为所述每个图像块内像素点的亮度均值、亮度方差、最大亮度值、最小亮度值或亮度的直方图统计值。
  24. 如权利要求17-23中任一项所述的视频编码器，其特征在于，所述的多个图像块中的至少两个图像块对应同一个光电转换函数。
  25. 如权利要求17-24中任一项所述的视频编码器，其特征在于，所述确定单元具体用于根据所述多个图像块中的任意一个第一图像块的亮度的统计值，确定所述第一图像块对应的光电转换函数；确定除所述第一图像块之外剩余的图像块与所述第一图像块之间的亮度的相关性；根据所确定的亮度相关性，确定所述剩余的图像块是否与所述第一图像块共用相同的光电转换函数；当确定所述剩余的图像块与所述第一图像块共用相同的光电转换函数时，将所述第一图像块对应的光电转换函数确定为所述HDR图像帧对应的全局光电转换函数；当确定所述剩余的图像块中存在与所述第一图像块不能共用相同光电转换函数的图像块时，根据所述剩余的图像的亮度的统计值，确定所述剩余图像块各自对应的光电转换函数。
  26. 一种视频解码器，其特征在于，包括：
    解码单元，用于解码码流以重建高动态范围HDR图像帧，所述HDR图像帧包括多个图像块；
    获取单元，用于从所述码流中获取多个图像块中的每个图像块的光电转换信息，所述光电转换信息由编码端基于所述每个图像块对应的编码块的亮度的统计值确定，且所述光电转换信息用于解码端确定所述每个图像块对应的电光转换函数；
    确定单元，用于根据所述每个图像块的光电转换信息，从预设的多个电光转换函数中确定所述每个图像块对应的电光转换函数；
    电光转换单元，用于根据所述每个图像块对应的电光转换函数，对所述每个图像块进行电光转换。
  27. 如权利要求26所述的视频解码器，其特征在于，所述光电转换信息包括用于指示所述每个图像块的电光转换函数的索引的索引信息，其中，所述索引信息是所述编码端基于所述每个图像块对应的光电转换函数的索引确定的，所述确定单元具体用于根据所述每个图像块的电光转换函数的索引，从所述预设的多个电光转换函数中确定所述每个图像块对应的电光转换函数。
  28. 如权利要求26所述的视频解码器，其特征在于，所述光电转换信息包括所述每个图像块对应的编码块的亮度的统计值，所述确定单元具体用于根据所述每个图像块对应的编码块的亮度的统计值，分别确定所述预设的多个电光转换函数的函数值；从所述多个电光转换函数的函数值中选取与预 设值差异最小的目标函数值；将所述目标函数值对应的电光转换函数确定为所述每个图像块对应的电光转换函数。
  29. 如权利要求26所述的视频解码器，其特征在于，所述光电转换信息包括所述每个图像块对应的编码块的亮度的统计值，所述确定单元具体用于确定所述每个图像块对应的编码块的亮度的统计值所落入的第一数值区间，其中，所述第一数值区间为预设的多个数值区间中的一个；根据所述多个数值区间与所述多个电光转换函数的一一对应关系，将所述第一数值区间对应的电光转换函数确定为所述每个图像块对应的电光转换函数。
  30. 如权利要求26-29中任一项所述的视频解码器，其特征在于，所述光电转换信息包括所述每个图像块对应的编码块的亮度的统计值，所述确定单元具体用于根据所述多个图像块中的任意一个第一图像块对应的编码块的亮度的统计值，确定所述第一图像块对应的电光转换函数；确定除所述第一图像块之外剩余的图像块对应的编码块与所述第一图像块对应的编码块之间的亮度的相关性；根据所确定的亮度相关性，确定所述剩余的图像块是否与所述第一图像块共用相同的电光转换函数；当确定所述剩余的图像块与所述第一图像块共用相同的电光转换函数时，将所述第一图像块对应的电光转换函数确定为所述HDR图像帧对应的全局电光转换函数；当确定所述剩余的图像块中存在与所述第一图像块不能共用相同电光转换函数的图像块时，根据所述剩余的图像对应的编码块的亮度的统计值，确定所述剩余图像块各自对应的电光转换函数。
  31. 如权利要求26-30中任一项所述的视频解码器，其特征在于，所述光电转换信息包括所述每个图像块的以下信息中的至少一种：
    用于指示所述每个图像块对应的电光转换函数的索引的索引信息；
    用于指示所述每个图像块对应的电光转换函数的参数的信息；以及
    所述每个图像块对应的编码块的亮度的统计值。
  32. 如权利要求26-31中任一项所述的视频解码器，其特征在于，所述统计值为所述每个图像块对应的编码块内像素点的亮度均值、亮度方差、最大亮度值、最小亮度值或亮度的直方图统计值。
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