Classifications

• • 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
  • H04N19/60—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding
  • H04N19/63—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding using sub-band based transform, e.g. wavelets
• • 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
  • H04N19/157—Assigned coding mode, i.e. the coding mode being predefined or preselected to be further used for selection of another element or parameter
  • H04N19/159—Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction
• • 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
  • H04N19/134—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
  • H04N19/134—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
  • H04N19/146—Data rate or code amount at the encoder output
  • H04N19/147—Data rate or code amount at the encoder output according to rate distortion criteria
• • 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
  • H04N19/174—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 slice, e.g. a line of blocks or a group of blocks
• • 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
  • H04N19/189—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
  • H04N19/192—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 the adaptation method, adaptation tool or adaptation type being iterative or recursive
  • H04N19/194—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 the adaptation method, adaptation tool or adaptation type being iterative or recursive involving only two passes
• • 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
  • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
  • H04N19/593—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving spatial prediction techniques
• • 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
  • H04N19/60—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding
  • H04N19/61—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding in combination with predictive coding

Definitions

• the present invention relates to a dynamic quantization method for encoding data streams. It applies in particular to the compression of videos according to the H.264 standards (as defined by the ITU (International Telecommunication Union) otherwise designated by MPEG4-AVC by the International Organization for Standardization (ISO)) and H.265 . More generally, the present invention applies to encoders comprising a quantization step in which different quantization coefficients can be applied according to the types of image blocks to be encoded.
• H.264 standards as defined by the ITU (International Telecommunication Union) otherwise designated by MPEG4-AVC by the International Organization for Standardization (ISO)
• H.265 More generally, the present invention applies to encoders comprising a quantization step in which different quantization coefficients can be applied according to the types of image blocks to be encoded.
• Quantization is a well-known step in MPEG video coding which allows after transposition of image data in the transformed domain (also referred to as the "transform domain"), to sacrifice the higher order coefficients to decrease substantially the size of the data by only moderately affecting their visual rendering. Quantification is therefore an essential step in lossy compression. In general, it is also the one that introduces the most important artifacts into the encoded video, especially when the quantization coefficients are very high.
• FIG. 1 illustrates the place 101 occupied by the quantization step in a coding method according to the MPEG4-AVC standard.
• the coding complexity and the amount of information to keep to ensure an acceptable output quality varies over time, depending on the nature of the sequences contained in the stream.
• Known methods can encode an audio or video stream by controlling the rate (bitrate) of output data. Some of these methods rely on a double pass quantization in which the first pass makes it possible to generate flow requests to an allocator according to the complexity of the video sequence, the second pass coding the sequence at the bit rate allocated by the allocator.
• the quantization level applied in the second pass plays, in this context, the role of an adjustment variable making it possible to reach the desired flow rate.
• the quality of the video can fluctuate until it degrades at times below a visually acceptable level.
• One way to guarantee a minimum level of quality over the entire duration of the flow is then to increase the throughput, which proves to be expensive and sub-optimal in terms of the use of material resources.
• Variable rate streams can also be generated, the throughput increasing in relation to the complexity of the scene to be encoded.
• this type of flow does not always match the constraints imposed by transport infrastructures. Indeed, it is common that a fixed bandwidth is allocated on a transmission channel, thus forcing to allocate a bandwidth equal to the maximum flow encountered in the stream to avoid transmission anomalies.
• this technique produces a flow whose average flow is substantially higher, since the flow must be increased at least temporarily to preserve the quality of the most complex scenes.
• An object of the invention is to reduce the bandwidth occupied by a stream encoded according to a standard of the MPEG type, or to increase the quality perceived by the observer of this flow at equal flow elsewhere.
• the subject of the invention is a method of dynamically quantizing an image stream comprising blocks of different types transposed in the transformed domain, the method comprising a first step of quantizing several of said blocks with coefficients of initial quantization, the method being characterized in that it comprises a step of determination, for several types of blocks respectively, of the residual coding costs after said first quantization, and a second step of quantizing the transposed blocks of at least one type with quantization coefficients chosen according to the distribution of said residual costs between several types of blocks.
• the first quantization step can be considered as a pre-quantization performed in order to determine the distribution of the residual costs between different types of blocks, that is to say for example the ratio between the costs induced by a first type of block and the costs of a second type of block.
• This distribution is then used in the second quantification step to arbitrate the debit allocation between several types of blocks and / or between the components of the transformed domain of the same type of block.
• the initial quantization coefficients may be predetermined to perform a compromise according to a compromise defined in advance, for example as a function of the transformed image sequences that can be quantized.
• the coefficients used for the second quantification step are based on the distribution of residual costs and, for example, pre-defined psycho-visual criteria, in order to minimize the quality degradation due to quantification while limiting the use of bandwidth when transporting data.
• the quantization coefficients used by the method according to the invention to quantify the transformed macroblocks must not be confused with the quantization parameter, also called mb_qp_delta in the MPEG4-AVC standard, which parameter is transmitted for each macroblock. of the image and makes it possible to deduce the global scalar quantization to be applied to the set of frequency coefficients.
• the dynamic quantization method according to the invention can perform an adjustment at a finer level, since it is able to adjust the scalar coefficients for each of the frequency coefficients from the transform.
• a plurality of sets of coefficients are pre-calculated and, during the second quantization step, coefficients of a set chosen from said plurality are applied.
• coefficients can thus be calculated in advance, each configuration being associated with a set of quantization coefficients.
• the coefficients are grouped in matrices, thus forming quantization matrices.
• One set of dice among several is then chosen during the second quantization step.
• one indicator or several indicators of residual cost distribution between several types of blocks are calculated, the definition domain of said indicators is partitioned into a plurality of value domains, associates a set of pre-calculated coefficients with each of said domains, and one chooses the set of coefficients to be applied during the second quantization step among said sets as a function of the value of said indicators.
• the value domain can be reduced to a plurality of value ranges.
• the quantized blocks during the first quantization step comprise chrominance blocks and luminance blocks transposed in the transformed domain, and in which the quantization coefficients are chosen.
• applied in the second step at least in part according to the ratio of the residual costs due to the chrominance blocks to the residual costs due to the luminance blocks.
• the image blocks are decomposed into a plurality of colorimetric components which are transposed in blocks into the transformed domain and on which prequantization coefficients are applied, the distribution of the residual coding costs of the blocks of blocks is determined.
• the image between the different colorimetric components, the transposed blocks are quantified in the transformed domain with coefficients chosen according to said distribution.
• the quantization coefficients associated with the lower-order components of the chrominance blocks are reduced, in relation with the decrease in the residual costs due to to chrominance blocks versus residual costs due to luminance blocks.
• lower-order components we mean the low-valued components in the transformed domain, in other words the low frequency components in the frequency domain, for example the components corresponding to a frequency less than or equal to a predetermined value.
• the quantized blocks during the first quantization step comprise spatial predictive coding blocks and temporal predictive coding blocks transposed in the transformed domain, and in which one chooses the quantization coefficients applied during the second step at least in part based on the ratio of residual costs due to space-predictive coding blocks to residual costs due to time-predictive coded blocks.
• the residual coding costs at the end of the pre-quantization are determined separately, then a quantification is applied. with distinct coefficients for each block type and determined according to said relative coding costs.
• spatially predictive coding block and “temporal predictive coding block” may be understood to mean, respectively, “block whose coding is of spatial predictive type” and “block whose coding is of temporal predictive type”.
• block included in an image whose blocks are all spatially predictive coding and “block included in an image comprising blocks with temporal predictive coding”.
• the quantization coefficients associated with the spatially predictive coded blocks are decreased, and the quantization coefficients associated with the prediction-coded blocks are increased. temporal, in relation to the decrease in residual costs due to time-predictive coded blocks compared to residual costs due to spatial predictive coding blocks.
• the quantization coefficients applied during the second quantization step to a same type of block or to the same set of block types in a matrix of the same are grouped together and stored. quantification.
• the stream to be encoded may be MPEG standard (for example MPEG4, ie H.264), and a set of quantization matrices chosen dynamically according to the residual cost distribution may include:
• the subject of the invention is also a method for encoding an image flow forming a video, comprising a step of block transformation of the images in the transformed domain, in which a dynamic quantization method as described above is executed. on said blocks.
• the stream can be encoded according to an MPEG standard.
• the dynamic quantization method is applied cyclically over a reference period equal to one group of MPEG images.
• the invention also relates to a video encoder, for example MPEG, configured to execute the decoding method as described above.
• a video encoder for example MPEG
• the subject of the invention is also a method for decoding an image stream encoded by an MPEG encoder as described above, the decoder being configured to find, from said coded image stream, the quantization coefficients used. by the encoder to quantize the data blocks.
• the quantization matrices can be found in the stream if they have been inserted by the encoder, or found by an identifier inserted in the stream, the decoder then having a memory for recording the different quantization matrices that can be used.
• the invention also relates to an MPEG video decoder, configured to execute the coding method as described above.
• FIG. 1 a block diagram illustrating an encoding method according to the MGEG4-AVC standard in which the method according to the invention can be used, this figure having already been presented above;
• FIG. 2 a block diagram illustrating an exemplary dynamic quantization method according to the invention.
• the nonlimiting example developed subsequently is that of the quantization of an image stream to be encoded according to the H.264 / MPEG4-AVC standard.
• FIG. 2 presents a block diagram illustrating an exemplary dynamic quantization method according to the invention. This comprises a first quantization step 201, a step of determining the relative residual coding costs 202, a quantization coefficients selection step 203, and a second quantization step 204 using the previously chosen coefficients.
• the images to be encoded are cut into macroblocks.
• Each macroblock corresponds to an image portion and is decomposed into a plurality of components, according to a chosen colorimetric system.
• a macroblock of the H.264 standard can be defined as a combination of blocks including the luminance and chrominance information.
• the chrominance blocks are of different sizes.
• the macroblocks have a size of 16x16 pixels.
• These macroblocks consist of 8x8 or 4x4 pixel blocks including luminance and chrominance information.
• the blocks are transformed in the transformed domain by a DCT (Discrete Cosine Transform) for the purpose of visually acceptable compression by quantization.
• DCT Discrete Cosine Transform
• some are coded according to a spatial predictive coding mode (also termed "intra” to mean that the coding does not depend on an image other than that in which the block is located), others according to a predictive mode (also qualified by the term “inter” to denote blocks whose coding depends on at least one other image than that in which it is located).
• the blocks 210 resulting from the transformation step in the transformed domain are subject to a first quantization 201 in order to measure the residual coding costs. Residual values of transformed components are obtained at the end of this first quantization 201, so that for each quantized block, it is possible to determine the residual coding cost, in other words the number of bits necessary to code the residual values after quantization. At the end of this first quantization, therefore, residual coding costs are obtained for each type (or category) of block: chrominance block, luminance block, block coded in intra mode, coded block in inter mode, for example.
• the block types can be considered by crossing several categories among themselves: for example, an intra type block can be at the same time a chrominance type block; the residual coding costs for the "intra-chrominance" blocks can then be considered. It is thus possible to partition the space of the block types according to multiple possibilities, another example consisting in considering only two types of blocks: a first type, for example luminance blocks coded intra, and a second type grouping together all other possible categories of blocks.
• the classification of the blocks into different types may depend on the type of image to which this block belongs.
• MPEG images of type P (with temporal prediction) and B (with bidirectional prediction) mainly comprise blocks with temporal predictive coding.
• this may also include spatial predictive coding blocks.
• the type of block considered for the calculation of the residual costs as that of the type of the image to which this block belongs, so that a block with spatial predictive coding present in an image (B or P) whose coding is predominantly temporal predictive is considered to be involved in the residual costs of inter-type images, thus considered as "inter" type.
• the initial coefficients 21 1 chosen to quantize the data during this first quantization 201 are different according to the type of block.
• a quantization matrix by block type is used.
• eight different matrices can be defined:
• ⁇ six matrices for 4x4 pixel blocks one for Intra 4x4 Y (luminance) blocks, one for Intra 4x4 Chroma U blocks (Chrominance U), one for Intra 4x4 Chroma V blocks, one for Inter 4x4 Y blocks, one for Inter 4x4 Chroma U blocks, and one for Inter 4x4 blocks.
• the block types considered in the calculation of the residual coding costs can be decoupled from the types associated with the quantization matrices.
• the coefficients 21 1 chosen to quantize the data during this first quantization 201 can be predetermined in advance for correspond to an average compromise for all types of video sequences.
• eight series of residual costs are obtained, each series comprising the residual cost measures for each of the quantized blocks in the corresponding type.
• a first series of residual costs is obtained for intra 4x4 Y type blocks, a second for intra 4x4 U type blocks, and so on.
• Residual costs belonging to the same series may be summed over a reference period, for example a group of images, a group of images comprising a plurality of images, the first of which is generally spatially predictive coded, the other images of the group may include time predictive coded blocks based on the blocks comprised by one or more other images of said group, so that knowledge of only group images is sufficient to decode said group.
• a group of images may for example be a group of images in the sense of the standard H.264 (or MPEG), more commonly referred to in the H.264 standard by the acronym GOP for "Group Of Pictures".
• the first quantization step 201 may for example be performed on a set of images forming a GOP, so that an overall residual cost can be calculated for the whole GOP on each of the types of blocks. to quantify.
• eight cost values for the GOP are thus obtained, each value being equal to the sum of the residual costs obtained respectively in each block type on all the GOP images.
• These residual total costs are noted as follows: C
• Reference periods for the calculation of the total residual costs are possible, for example a period comprising several GOPs, or a period less than that of a GOP.
• the first quantization 201 is performed only on a sample of the transformed image blocks 210 input, the residual costs resulting in this case only from the quantification of blocks making up the sample.
• the residual costs determined during the first quantization step 201 are used to calculate indicators. These indicators may in particular be equal to residual cost ratios relating to different types.
• NT RA_4X4_V) i.e., 11 is equal to the ratio between the residual coding costs of the inter mode blocks and the intra mode blocks.
• This indicator 11 makes it possible to determine the relative weights of the spatial and temporal information in the coding of the images.
• CINTER_8 XS _Y in other words the ratio between the residual coding costs of the chrominance blocks and the luminance blocks.
• This indicator 12 makes it possible to determine the relative weights of the chrominance and luminance information in the coding of the images. Other indicators can thus be calculated to determine the information density of certain types of blocks compared to other types. The indicators therefore make it possible to know at least in part the distribution of the residual costs between the different types of blocks to be coded.
• the indicators determined in the previous step 202 are used to choose sets of coefficients to be used during the quantization of the data.
• the coefficients are chosen according to indicators and psycho-visual criteria to improve the visual rendering of the video.
• the sequence of images is complex from the point of view temporal.
• the scene represented by the sequence of images includes moving objects, the human eye of which would not be able to perceive the many texture details.
• the human visual system applies an integrating filter that ignores the many details in the moving masses, but is sensitive to the fluidity of movement.
• a more severe quantization is preferably applied to the information encoded in intra mode to leave sufficient flow available to the coded information in inter mode and thus better preserve the movement.
• the coefficients of the quantization matrices corresponding to the Intra types are increased and those corresponding to the Inter types are decreased.
• the coefficients of the matrices relating to the types of blocks Intra 4x4 Y, Intra 4x4 Chroma U, Intra 4x4 Chroma V, and Intra 8x8 Y are increased and those of matrices Inter 4x4 Y, Inter 4x4 Chroma U, Inter 4x4 Chroma V and Inter 8x8 Y are decreased.
• this ratio 11 is low - for example, if the image sequence to be encoded represents a scene in slight motion -, preservation of the intra data is to be preferred and the coefficients of the Intra type matrices are decreased. Inter type being increased, by compensation. In this way, the quality of the details is improved for the whole scene, because the better quality of the reference image encoded in Intra propagates to the temporal prediction images, which benefit from a simple temporal prediction in this type. sequences.
• several sets of quantization matrices are predetermined and selected according to the indicators, a set of matrices comprising, in the example, eight quantization matrices.
• the set of matrices chosen may depend jointly on the values of 11 and 12.
• the domain of the values of each indicator is partitioned in several intervals, so that the values of the matrix coefficients are different when the value of a indicator goes from one interval to another.
• a set of matrixes per pair of intervals can thus be prepared in advance, so that in the general case, the number of games available for the second quantization 204 is equal to the product of the number of intervals in each domain of values. indicators.
• the sets of matrices are not precalculated and the coefficients of the matrices are computed on the fly according to the values of the indicators.
• the quantization coefficients are chosen directly from the residual costs calculated from the first quantization 201; in other words, no intermediate indicator is calculated.
• a second quantization 204 is performed on the input data using the quantization coefficients determined in the previous step 203.
• the set of eight matrices corresponding to the indicator values obtained is used for the second quantization 204.
• the input data that was quantized during the first quantization 201 is delayed over a reference period - in the example, a GOP -, so as to quantize these same input data with the set of matrices chosen according to indicators and not with the predetermined matrix set used during the first quantization pass 201.
• only certain types of blocks, or even only one, are subject to dynamic quantization.
• this dynamic quantization depends on the distribution of residual costs between different block types, to assess their relative complexity levels, and to allocate more throughput for the least expensive components. more complex and critical from the point of view of the visual rendering.
• the output data rate can be regulated, for example, by a quantization step adjusted according to the bandwidth allocated to the output stream.
• the video stream 240 from the second quantization step 204 can then be entropically coded to complete the compression and produce an output MPEG stream.
• the "coefficient of quantification” is the factor of a coefficient used to quantify the data; this "quantization coefficient” can be multiplied by a scalar quantization step to adapt the output data rate.
• the dynamic quantization method according to the invention can be applied cyclically on a video stream to be encoded.
• the quantization matrices are updated according to a period equal to the reference period mentioned above, for example a GOP.
• the method cyclically applies a first quantization pass with a set of predefined and fixed matrices in order to determine residual coding costs for several types of blocks, and then applies on the same stream a second quantization pass.
• 204 with matrices with appropriately chosen coefficients.
• An MPEG encoder can thus be configured to execute a dynamic quantization method in place of a conventional quantization method, so as to preserve better visual rendering at equivalent compression level, or to obtain a better level of compression at equivalent quality.
• the encoder may comprise a memory recording the different sets of quantization coefficients that may be used, a calculation unit (programmable circuit for example) configured to calculate residual costs, relative cost indicators and to choose the set of coefficients the more adapted.
• the encoder can insert the quantization matrices in the output stream, so that a decoder receiving this stream can use these matrices to decode the blocks.
• the encoder comprises a memory recording the different sets of matrices available for quantization and inserts, in the output stream (resulting from the quantization), an identifier of the set of matrices used for quantification.
• An associated decoder stores equivalent matrices in a memory and uses the identifier present in the stream to find the set of matrices used for the quantization.
• the dynamic quantization method according to the invention makes it possible to modify the bandwidth assignments between the different types of data to be coded according to the relative importance of each of these data in the preservation of the quality of the video. It also makes it possible to modify the flow distribution for the same type of blocks by increasing or decreasing certain quantization coefficients according to the distribution of the residual costs due to different types of blocks.
• the dynamic quantization method according to the invention makes it possible to adapt the quantization levels applied to certain visual parameters (for example the chrominance) as a function of the relative evolution of other visual parameters (for example luminance).
• the dynamic quantization method according to the invention can for example be used in H.264 / MPEG4-AVC video stream encoders HD (high definition) or SD (standard definition), without however being limited to the standard H.264, the a method that can more generally be used when encoding streams comprising several types of data (inter or intra, luminance or chrominance, for example), whether these data are images, slices of images, or more generally sets of pixels that can take the form of blocks. Each of these data comprising information of different types can then be quantified optimized according to the relative residual costs between different types of data.
• the method according to the invention is also applicable to coded streams of other standards such as MPEG2.

Landscapes

• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Compression Or Coding Systems Of Tv Signals (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=47435999

Family Applications (1)

Country Status (4)

Families Citing this family (1)

Family Cites Families (5)

• 2012
  • 2012-01-17 FR FR1250480A patent/FR2985879A1/fr active Pending
  • 2012-12-21 EP EP12806496.1A patent/EP2805486A1/de not_active Withdrawn
  • 2012-12-21 WO PCT/EP2012/076626 patent/WO2013107600A1/fr not_active Ceased
  • 2012-12-21 US US14/372,927 patent/US20150010073A1/en not_active Abandoned

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events