WO2009071881A1 - Codage de données auxiliaires dans un cadre d'image - Google Patents

Codage de données auxiliaires dans un cadre d'image Download PDF

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Publication number
WO2009071881A1
WO2009071881A1 PCT/GB2008/003985 GB2008003985W WO2009071881A1 WO 2009071881 A1 WO2009071881 A1 WO 2009071881A1 GB 2008003985 W GB2008003985 W GB 2008003985W WO 2009071881 A1 WO2009071881 A1 WO 2009071881A1
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WO
WIPO (PCT)
Prior art keywords
block
window
auxiliary data
image frame
value
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/GB2008/003985
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English (en)
Inventor
Wilhelmus Hendrikus Alfonsus Bruls
Rudi Jozef Marie Wijnands
Rene Barto
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Ambx UK Ltd
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Ambx UK Ltd
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Filing date
Publication date
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Priority to GB1009202A priority Critical patent/GB2468981B/en
Publication of WO2009071881A1 publication Critical patent/WO2009071881A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/32—Circuits or arrangements for control or supervision between transmitter and receiver or between image input and image output device, e.g. between a still-image camera and its memory or between a still-image camera and a printer device
    • H04N1/32101—Display, printing, storage or transmission of additional information, e.g. ID code, date and time or title
    • H04N1/32144—Display, printing, storage or transmission of additional information, e.g. ID code, date and time or title embedded in the image data, i.e. enclosed or integrated in the image, e.g. watermark, super-imposed logo or stamp
    • H04N1/32149—Methods relating to embedding, encoding, decoding, detection or retrieval operations
    • H04N1/32154—Transform domain methods
    • H04N1/32165—Transform domain methods using cosine transforms
    • 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
    • H04N19/48—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using compressed domain processing techniques other than decoding, e.g. modification of transform coefficients, variable length coding [VLC] data or run-length data
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/32—Circuits or arrangements for control or supervision between transmitter and receiver or between image input and image output device, e.g. between a still-image camera and its memory or between a still-image camera and a printer device
    • H04N1/32101—Display, printing, storage or transmission of additional information, e.g. ID code, date and time or title
    • H04N1/32144—Display, printing, storage or transmission of additional information, e.g. ID code, date and time or title embedded in the image data, i.e. enclosed or integrated in the image, e.g. watermark, super-imposed logo or stamp
    • H04N1/32149—Methods relating to embedding, encoding, decoding, detection or retrieval operations
    • H04N1/3232—Robust embedding or watermarking
    • H04N1/32325—Robust embedding or watermarking the embedded data being visible
    • 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
    • H04N19/467—Embedding additional information in the video signal during the compression process characterised by the embedded information being invisible, e.g. watermarking
    • 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
    • H04N19/85—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using pre-processing or post-processing specially adapted for video compression
    • H04N19/89—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using pre-processing or post-processing specially adapted for video compression involving methods or arrangements for detection of transmission errors at the decoder

Definitions

  • This invention relates to a method and device for encoding auxiliary data in an image frame, and to a method and device for decoding the auxiliary data from an image frame, a signal comprising the image frame contained encoded auxiliary data and to a record carrier containing the signal.
  • the invention provides, in one embodiment, a very robust embedding method for embedding auxiliary data in MPEG video frames, using frequency modulation principles.
  • a signal is transferred which includes the video data (normally with audio data).
  • some form of additional data is also included in the signal.
  • the signal in a digital television system, it is common for the signal to include a data portion, which includes such things as an electronic program guide and interactive applications, which the end user receives and can access at the same time as watching the video component of the signal.
  • United States Patent US 5940134 discloses a method and arrangement for marking a video or audio signal to assign a classification to said signal, for example, to identify that the signal is authentic and may not be copied.
  • the signal comprises at least two components (Y, UV) according to a predetermined standard (MPEG, PAL, NTSC).
  • MPEG MPEG, PAL, NTSC
  • values are assigned to the components, which in combination can normally not occur. For example, in black picture portions where Y, U and V are all zero, U and/or V are now willfully made non-zero to constitute the watermark. Television receivers still display the black portion. The watermark is not lost when the signal is re-encoded and copied on a recordable disc.
  • This prior art patent describes the possibility of encoding user-data in black video portions. It describes the possibility to encrypt this user-data in the color information (chrominance) of a video frame without the consumer noticing this, while the intensity (luminance) of each of the pixels in this frame is set to zero, hi this way a black portion is shown to the user.
  • a significant problem with respect to showing these augmenting effects in concurrency with the playback of AV content is the fact that the augmenting script for a specific AV content has to be available at the rendering location. For example, if the user is watching DVD on a conventional DVD player, access to and execution of the augmenting scripts has to be arranged. Particularly in cases where no connection to the Internet is present, some method of assisting the distribution of the augmenting scripts is required. To achieve this, it is possible to distribute the user-data via some other distribution medium, which however requires the availability of this medium. Another option would be the inclusion of a particular user-data file on the disc. This however requires the adaptation of disc-formats, disc-player devices, and probably also the external interface of disc-player devices.
  • data can be included in the video stream directly, but all of the known systems require some amendment to the receiving device so that the data (such as the augmenting scripts) can be accessed and retrieved from the signal and/or some amendment is needed to the original device which is encoding the video data into a form to be carried by the ultimate signal and/or only a relatively small amount of data is included in the image.
  • a method of encoding auxiliary data in an image frame comprising dividing the image frame into one or more rectangular blocks, for at least one block within the image frame: transforming the block from the pixel to the frequency domain, defining a rectangular window within the transformed block, receiving auxiliary data, mapping a component of the auxiliary data to a position in the window, and inserting a luminance value in the mapped position.
  • a device for encoding auxiliary data in an image frame comprising a processor arranged to divide the image frame into one or more rectangular blocks, and for at least one block within the image frame is arranged to transform the block from the pixel to the frequency domain, to define a rectangular window within the transformed block, to receive auxiliary data, to map a component of the auxiliary data to a position in the window, and to insert a luminance value in the mapped position.
  • a method of decoding auxiliary data from an image frame comprising receiving an image frame, dividing the image frame into one or more rectangular blocks, for at least one block within the image frame: transforming the block from the pixel to the frequency domain, defining a rectangular window within the transformed block, detecting the highest peak in the window, mapping the position of the detected peak to a value according to a predefined scheme, and creating a component of auxiliary data from the value.
  • a device for decoding auxiliary data from an image frame comprising a receiver arranged to receive an image frame, and a processor arranged to divide the image frame into one or more rectangular blocks, and for at least one block within the image frame is arranged to transform the block from the pixel to the frequency domain, to define a rectangular window within the transformed block, to detect the highest peak in the window, to map the position of the detected peak to a value according to a predefined scheme, and to create a component of auxiliary data from the value.
  • auxiliary data in an image frame, in such a way that the data will survive the communication path of the image frame and will survive the conversion of the image frame into an analogue output.
  • auxiliary data By including a peak at a specific position in a transformed block, and encoding data by position, it is easier to detect the position of a peak in a block, rather than attempting to accurately determine the value of any peak.
  • the invention provides a solution for disc-based audio/video content delivery (for example DVD, Blu-ray Disc) where the content is afterwards transported via an analogue data-path.
  • the encoding method provides efficient (i.e. providing a very good ratio between net and gross information) and robust embedding of information.
  • this is achieved by making use of a clever way of amplitude modulation within a (pre-selected) window within a DCT block, completely filled with AC (DCT) coefficients.
  • DCT AC
  • the problem with this type of application is that the analogue path is very unpredictable, for example, with unknown processing in the receiving device such as DVD player, and cable reflections etc in the analogue output of the DVD player.
  • This re-sampling is not locked with respect to the original data in the digital domain, at least not in phase, which means the re- sampled data can be kind of interpolated.
  • the problems with the data path are magnified when lowering the visibility of the embedded auxiliary data and working with lower (darker) luminance values.
  • the method of encoding further comprises mapping a second component of the auxiliary data to a second position in the window, and inserting a luminance value in the mapped second position. It is possible to insert a second peak into a block and thereby carry more information in the image frame.
  • the block size is 8x8 pixels
  • the window size is 3x3 pixels
  • the step of defining a rectangular window within the block comprises defining a window in the top left hand corner of the block.
  • the low frequency components in an 8x8 macroblock are shifted towards the top left hand corner of the block following DCT conversion. These low frequency components are more robust in relation to the overall signal once broadcast, decoded and displayed. It is therefore advantageous to insert amplitude peaks in this part of the block (as defined by the window) to improve the robustness.
  • the method can further comprise inserting an average luminance value of the block in the top left hand corner of the block, wherein the or each inserted luminance value in a mapped position has a value that is relative to the average luminance value of the block.
  • the average luminance value of the block in the top left hand corner of the block (the DC coefficient in MPEG 2) can be set at, for example 20, and then the inserted luminance value could be +5 or -5 (giving a value of 25 or 15) which, when using the 3x3 window allows 4 bits to be used in the embedded data.
  • There are 8 positions available in the 3x3 window (one being used by the DC coefficient), giving 3 bits, and the sign of the inserted luminance value giving the 4 l bit. In this example in the encoding all of the luminance values in the block, except the inserted luminance values, are set to zero.
  • Fig. 1 is a schematic diagram of a method of encoding auxiliary data in an image frame
  • Fig. 2 is a schematic diagram of a device for encoding the auxiliary data in an image frame
  • Fig. 3 is a schematic diagram of a rectangular block of an image frame
  • Fig. 4 is a schematic diagram of various image frames
  • Fig. 5 is a schematic diagram of a device for decoding the auxiliary data from an image frame
  • Fig. 6 is a schematic diagram of an image frame
  • Figs. 7 and 8 are schematic diagrams of image frames, showing the use of error correction
  • Fig. 9 is a schematic diagram of image frame and error correction frames.
  • Fig. 1 shows schematically the process of embedding auxiliary data 10.
  • This data 10 first passes to a compression stage 12, where one or more compression algorithms reduce the amount of data present, which is then passed to the embedding stage 14, where the embedding of the compressed auxiliary data 10 takes place.
  • the output of the embedding stage 14 is a bitstream 16.
  • the preferred embodiment of the invention is to utilize the video encoding scheme MPEG2 to create image frames that look predominately black to the user when they are displayed, but actually contain embedded auxiliary data 10, embedded according to the process described below.
  • the auxiliary data 10 is not in addition to the normal image in a frame (as in watermarking techniques) but one or more blocks in the frame (which may make up the entire frame) are utilized to embed the auxiliary data 10.
  • Fig. 2 shows an encoder 18, which is a device for embedding the auxiliary data 10, and ultimately creating a bitstream 16.
  • the encoder 10 comprises a video buffer 19 which is arranged to receive conventional video data 21 being frames making up a video sequence.
  • the video data 21 may be in the form of pixel data that still needs to be encoded into an MPEG stream, or may already be MPEG data that is to be combined with the auxiliary data 10 once that is encoded.
  • the device 18 also comprises a compression device 20 that is arranged to receive and compress the auxiliary data 10, as per the process of Fig. 1.
  • the auxiliary data 10 takes the form of one or more XML files which define scripts for use in the augmentation of an entertainment experience (such as a film) and take the form of one or more files with synchronization tables.
  • the data 10 is to be encoded by the device 18 into MPEG image frames.
  • a processor 22 in the encoder 18 is arranged to embed the auxiliary data 10 according to a defined scheme (discussed in more detail below with reference to Fig. 3) and thereby encoding the auxiliary data 10 as one or more image frames 24, each frame 24 substantially consisting of the embedded auxiliary data 10.
  • the processor 22 turns the auxiliary data 10 from its stored form (a bitstream representing an XML file) into a set of MPEG image frames 24.
  • These frames 24, when handled by, for example, a conventional MPEG decoder will look exactly like a valid MPEG stream, although if that I- frame is displayed by a suitable display device, it would simply be noise.
  • the frame 24 is shown in Fig. 2 as a group of blocks of white, gray and black, but this is for illustrative purposes only.
  • the embedding method discussed below will produce an image frame 24, that when displayed by a suitable display device will be predominantly black.
  • the frames 24 and the video data 21 are passed to a transmitter 23, which is arranged to combine the video data 21 and the image frames 24 into the bitstream 16.
  • the encoder 10 can output the bitstream 16 to a record carrier 25 (such as a conventional DVD), which stores the bitstream 16.
  • the compression block 20 is used because, while it is known that video codecs can remove redundancy from image files, they are not very efficient in removing the type of redundancy present in auxiliary data defining amBX (XML-like) data files, because video codecs are optimized on the basis that they are receiving real image files.
  • the compression is best done with algorithms such as ZIP, or RAR etc. This saves a factor of around four, and makes it much easier to realize a robust system, as shown in Fig. 1.).
  • the method of encoding the auxiliary data 10 in an image frame 24, carried out by the processor 22 is illustrated by Fig. 3.
  • the process of encoding comprises dividing the image frame 24 into one or more rectangular blocks 26, and, for at least one block 26 within the image frame 24, transforming the block 26 from the pixel to the frequency domain, using a transform such as discrete cosine transform DCT, defining a rectangular window 28 within the transformed block 26, receiving the auxiliary data 10, mapping a component of the auxiliary data 10 to a position 30 in the window 28, and inserting a luminance value ⁇ Ll in the mapped position.
  • a transform such as discrete cosine transform DCT
  • x-1 bits can be mapped to one AC coefficient in one of 2 ⁇ (x-l) positions in a DCT block, while all other AC coefficients are set to 0, as shown in Fig. 3.
  • Y2 is inserted an AC value with level Ll.
  • the sign of this AC value it is possible to encode one extra bit, so the total bits encoded in the block 26 is x bits per DCT block 26. Since low frequencies in the DCT are more robust than high frequencies, it makes sense to limit the locations within the DCT, for example, by a rectangular window of size X2 by Y2, giving a 3x3 window in the top left hand corner.
  • modulation is provided on low DC levels with small variations.
  • DC level (luminance) of 20 AC levels (Ll) of +/- 5 are sufficient. This will produce an image frame, that when displayed is predominately black.
  • the process of encoding the auxiliary data comprises applying on the data 10, firstly a ZIP, ARC, RAR, 7-Zip (LZMA) compression, and then the mapping of x number of aux bits to one or two (XIa, YIa) + (XIb, YIb) AC peak positions with level +Ll or -Ll within a window (X2, Y2), all other AC values are 0 (or close to 0).
  • At the receiving end detection is carried out by determining the location and sign of the maximum (absolute value) AC coefficient within the window (X2, Y2) or finding the 2 maximum values.
  • Table 1 shows an example of the net bitrate that it is possible to embed with this method, and the resulting bitstream rate for this example.
  • An image frame 24 can have multiple rectangular blocks 26 that have auxiliary data 10 encoded therein and indeed the entire frame 24 could consist of blocks 26 as described with reference to Fig. 3.
  • the majority of the frame 24 will consist of blocks 26 with data 10 encoded therein, with a small number of blocks within the frame 24 consisting of elements that will support the synchronization of the decoding apparatus.
  • the block 26 shown in Fig. 3 is shown after a DCT transform has taken place, but does not have quantization performed on it (as in a normal MPEG frame) but is run-encoded using MPEG VLC to form the bitstream 16.
  • Fig. 4 shows the effects on the video data from a DCT block with a peak at a certain position.
  • the picture shows 8 by 8 different versions of image data, corresponding to 8 by 8 different positions of a peak in a DCT block.
  • the upper left image data corresponds to a peak in the upper left (DC) position in the DCT
  • the upper right image data corresponds to a peak in the upper right position in the DCT (DC in vertical direction, high frequency in horizontal direction)
  • the lower left corresponds to a lower left peak position (DC in horizontal direction, high frequency in vertical direction)
  • DC in horizontal direction high frequency in vertical direction
  • this method is relatively computation intensive.
  • Fig. 5 shows an embodiment of the equipment at the receiving end of the chain.
  • the encoder 18 has its output (the bitstream 16) stored on the DVD 25, which can then be received by a standard DVD player 40.
  • the analogue output of that DVD player 40 can be used by a decoder 42, which will be able to access the auxiliary data 10, which is contained in the image frames 24.
  • the decoder 42 retrieves the analogue image frames 24, and applies the DCT transformation to each 8 x 8 block to obtain the DCT coefficients of each block. Since the decoder knows the values of the quantizer matrix Qi ntra (m,n) and the value of the quantizer scale q, it can compute the corresponding levels by division. From the position of these levels the bits can be retrieved by means of a look up table. The decoder 42 also knows in which order the DCT coefficients are written in the DCT blocks. Zero DCT levels do not present data and can be skipped. This is discussed in more detail below. The system of Fig. 5 is for handling the bitstream 16 at the receiving end.
  • the system might be at a location such as a consumer's lounge where they will watch a film that is stored on the DVD 25, and, in addition have an augmentation system present that will be able to use the auxiliary data 10.
  • the system comprises the DVD player 40 and the decoder 42.
  • the player 40 comprises a receiver 44, which is arranged to receive the bitstream 16 from the carrier 25, the bitstream 16 comprising a plurality of encoded image frames 24.
  • the DVD player 40 includes a conventional video decoder 46 which is arranged to decode the image frames 24, which are passed to a display device 48, which is arranged to display the video frames 24.
  • the video frames are also passed by the DVD player 40 to the decoder 42.
  • This connection can be a standard analogue output, as a DVD player receives a digital stream (MPEG) and converts this into an analogue stream for display by an analogue device such as the conventional television 48.
  • the decoder 42 includes a processor 50 which is arranged to execute an extraction process on the decoded video frames 24, the extraction process comprising decoding the auxiliary data 10 from the image frames 24.
  • the method of decoding the auxiliary data 10 from the image frame 24 comprises receiving the image frame 24, dividing the image frame 24 into one or more rectangular blocks 26, and then for each of the blocks 26 within the image frame 24, transforming the block 26 from the pixel to the frequency domain, defining the rectangular window 28 within the transformed block 26, detecting the highest peak in the window 28, mapping the position of the detected peak to a value according to a predefined scheme, and creating a component of auxiliary data 10 from the value.
  • the highest peak detected in the window 28 is assumed to represent the inserted luminance value embedded during the encoding phase, and any other peaks in the window constitute noise that have come into the block during the transmission path (at whatever point).
  • the preferred extraction (decoding) method is detection using DCT and looking for the maximum AC value within the defined window 28 (X2, Y2) of the blocks 26 within each frame 24.
  • measures are needed to align with DCT borders, i.e. the processor 50 has to work out where in an image frame 24 the actual blocks 26 are located.
  • An extra advantage of the frequency modulation as described above is that for every block a fine-tuning signal can be derived easily, such that alignment can be done on a DCT block basis.
  • a two-step approach can be followed. Firstly special borders containing two kinds of empty DCT blocks with two different luminance values can be used for coarse alignment. Then fine-tuning can be performed based on minimizing the residual energy (energy of the all AC in DCT block except the maximum one).
  • the found optimal refinement parameter is passed on to the next DCT block to be detected.
  • This approach can also be used to detect whether image lines (fields) have been swapped (odd and even field swapping). After all this processing, it can safely be assumed that the DCT borders are very well aligned. Detection is now relatively straightforward for the processor 50, perform DCT, find the location (frequency) of absolute maximum (MAX) AC value within the known window (X2, Y2). Determine the sign of this MAX AC value.
  • the x bits embedded in this DCT are known (x-1 bits from the position, 1 bit from the sign of the peak).
  • Another advantage of the frequency method is that for every detected DCT block there is also received an indication of the reliability of the detection.
  • this DCT block can be flagged as unreliable (an erasure).
  • ECC error correction systems performance
  • Fig. 6 shows an example of a complete image frame 24 containing the frequency modulated auxiliary data 10 encoded as blocks 26 and marker patterns 52 for the coarse DCT block alignment plus two extra DCT columns 54 for fine-tuning the coarse DCT block alignment after the coarse alignment.
  • a dynamic alignment can be performed as well (for example, when there is a small horizontal zoom present is the picture or when the sync - video signal dependency is causing some non-homogeneous behavior within one frame with respect to horizontal alignment).
  • auxiliary data 10 within the image frame 24 can be improved, using multistage ECC (error correcting codes), which also provides OSD (on- screen display) resistance.
  • OSD resistance is needed to deal with the possibility of the user pressing a button on their remote control that will bring additional material onto the display device 48.
  • the decoder 42 is simply receiving the analogue output that goes to the display 48, so ay OSD will obscure some of the blocks 26 that are needed for the data extraction.
  • ECC horizontal and vertical error correction codes
  • Fig. 7 The image 24 shown in this Figure comprises rows of the rectangular blocks 26, which make up the majority of the frame 24.
  • a small number error correction blocks 56 are provided that provide a checksum, and therefore error correction, for the blocks 26 in the respective row.
  • columns of error correction blocks 56 are also provided, which have the same function as the row error correction blocks 56, providing error correction for the respective column.
  • the error correction function provided by the row and column error correction blocks 56 can be used to determine the missing value.
  • the error correction function provided by the row and column error correction blocks 56 can be used to determine the missing value.
  • 14 blocks for row ECC, out of 90, and 12 blocks for column ECC, out of 72 14 blocks for row ECC, out of 90. This is a simple, though not necessarily the best, example of how a simple error correction can be achieved.
  • the ratio of data blocks to ECC blocks can be changed to improve or decrease error correction capabilities.
  • FIG. 8 A more sophisticated arrangement is shown in Fig. 8, which provides a frame 24 that is more robust against the OSD overlays (triggered by a user action). Without this arrangement, the system would fail to extract the auxiliary data 10 every time that a user uses the remote control during the playback phase when the frames 24 that contain the auxiliary data are shown on the display device 48.
  • These OSD overlays normally have specific dimensions. The arrangement is such that the dimensions of a DATA block 58 in Fig. 8 are bigger than the size of a normal OSD overlay (in >95% of cases). As long as the OSD overlay does not cover more than three DATA blocks 58, the ECC function, provided by the parity blocks 60, of the arrangement of Fig. 8 allows the complete correction of the data 10 which is lost by the disturbance of the OSD overlay.
  • FIG. 9 An alternative or additional way of providing the error correction function is shown in Fig. 9.
  • P denotes the number of ECC frames 62
  • Fig. 8 is illustrating a spatial arrangement of the error correcting components
  • Fig. 9 is showing a temporal arrangement of the error correcting components.
  • error correction arrangements are possible. For example, by using CRC codes to signal erasures. It is possible to place a Cyclic Redundancy Code in the embedded data, such that after error correction it is possible to check whether the data was correctly recovered. This normally means adding a say 16 bit code to the data, and performing a CRC algorithm on the data to see whether the calculated CRC is equal to the stored CRC. If this is not the case, the data including the CRC could also be flagged as an erasure (error).
  • Frequency modulation can also be applied to two AC peaks, as shown in Table 3.
  • Table 3 Number of bits per DCT for 1 or 2 peaks in a 4 by 8 area
  • a number of processing refinements are possible in order to increase the accuracy and robustness of the decoding. For example, it is possible to refine DCT offset position based on minimal residual energy outside detected coefficient (absolute maximum).
  • the found optimal refinement parameter is passed on to the next to be detected DCT block. For example, if a peak is detected that is outside the expected window within a block then it is likely that the decoder has not selected the start point correctly for the blocks, and this can be corrected by shifting measurement by one or more pixels until the peak is located within the expected window.
  • the decoder can be configured to effectively "erase” a value detected in a block, if residual energy outside detected coefficient exceeds a predetermined threshold, i.e. by then flagging this DCT block as an erasure flag. Because the other components within the blocks are set to zero (except for the DC component and the one or two peaks inserted as AC components in the window of the block) then these values can be checked, and if they exceed a certain absolute value above zero, then the block can be flagged as error. This means that the block is one that has likely undergone sufficient change (through reflections in the analogue wire or whatever) that the position of the detected peak can no longer be relied on. Error correction blocks may be needed to determine the value encoded in the block.
  • auxiliary data 10 When the auxiliary data 10 is turned into image frames 24, these have to be added to the DVD 25.
  • One way that these frames 24 can be added is to use a separate (one additional) "DVD Title" (as defined in the DVD description, see http://www.dvd- replica.com/DVD/vtsguide.php) for the auxiliary data 10.
  • DVD Title as defined in the DVD description, see http://www.dvd- replica.com/DVD/vtsguide.php
  • the frames 24 that are used to embed the auxiliary data 10 support very easy insertion at the DVD authoring level.
  • the nature of the auxiliary data 10 is compatible with wide-screen (most movies); the lead-in can still be 4:3 (some DVD players may switch in some modes on wide-screen causing scaling at the analogue output).
  • the DVD can be configured to set the DVD to inhibit random access (fast forward, stop etc) during the output of the frames 24 that contain the auxiliary data 10, because this section contains real system data (for the auxiliary system) rather than video (for viewer) data.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Compression Or Coding Systems Of Tv Signals (AREA)
  • Compression, Expansion, Code Conversion, And Decoders (AREA)

Abstract

L'invention porte sur un procédé de codage de données auxiliaires dans un cadre d'image. Le procédé consiste à diviser le cadre d'image en un ou plusieurs blocs rectangulaires, pour au moins un bloc à l'intérieur du cadre d'image : transformer le bloc du domaine des pixels vers le domaine fréquentiel, définir une fenêtre rectangulaire à l'intérieur du bloc transformé, recevoir des données auxiliaires, mapper une composante des données auxiliaires à une position dans la fenêtre, et insérer une valeur de luminance dans la position mappée.
PCT/GB2008/003985 2007-12-04 2008-12-02 Codage de données auxiliaires dans un cadre d'image Ceased WO2009071881A1 (fr)

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GB1009202A GB2468981B (en) 2007-12-04 2008-12-02 Encoding auxiliary data in an image frame

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Application Number Priority Date Filing Date Title
EP07122301 2007-12-04
EP07122301.0 2007-12-04

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WO2009071881A1 true WO2009071881A1 (fr) 2009-06-11

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Citations (1)

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EP0926897A2 (fr) * 1997-12-24 1999-06-30 Sarnoff Corporation Méthode de traitement d'un signal vidéo pour l'insertion d'un filigrane électronique

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EP0926897A2 (fr) * 1997-12-24 1999-06-30 Sarnoff Corporation Méthode de traitement d'un signal vidéo pour l'insertion d'un filigrane électronique

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