Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
  • H04N21/20—Servers specifically adapted for the distribution of content, e.g. VOD servers; Operations thereof
  • H04N21/23—Processing of content or additional data; Elementary server operations; Server middleware
  • H04N21/236—Assembling of a multiplex stream, e.g. transport stream, by combining a video stream with other content or additional data, e.g. inserting a URL [Uniform Resource Locator] into a video stream, multiplexing software data into a video stream; Remultiplexing of multiplex streams; Insertion of stuffing bits into the multiplex stream, e.g. to obtain a constant bit-rate; Assembling of a packetised elementary stream
  • H04N21/2365—Multiplexing of several video streams
• • 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
  • H04N19/503—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving temporal prediction
  • H04N19/51—Motion estimation or motion compensation
• • 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
  • H04N19/40—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using video transcoding, i.e. partial or full decoding of a coded input stream followed by re-encoding of the decoded output stream
• • 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 encoding performed by the server is an encoding of the spatiotemporal type such as H264.
• the H264 standard is a video coding standard de- jointly developed by VCEG (Video Coding Experts Group) and MPEG (Moving Pictures Experts Group). This standard makes it possible to encode video streams with a bit rate less than two times less than that obtained by the MPEG2 standard for the same quality.
• a spatio-temporal encoding fully encodes only part of the images to be transmitted in order to reconstitute a video.
• the H264 standard contains the types of images known and defined in the MPEG2 standard, namely:
• a motion compensation module receiving motion vectors and providing at least one predicted zone, said coding system being characterized in that said data receiving module further receives a real motion vector of at least one displaced zone said current image, said coding system comprising: means for allocating said real motion vector to the macroblocks belonging to said displaced zone;
• macroblock denotes a rectangular elementary region of the image having a size between 4x4 and 16x16 pixels (via 8x16, 8x8, ).
• Each macroblock itself consists of luminance blocks and chrominance blocks.
• Motion estimation in the context of a spatiotemporal coding is an operation which requires a very important computing power.
• the system according to the invention makes it possible to overcome a part of this estimate by advantageously using the provision of an already existing motion vector. Thanks to the invention, the provision of the motion vector relative to a zone (typically a rectangle within a frame or "frame" in English) having been displaced makes it possible not to calculate the motion vectors for the macroblocks that are in such a moved area.
• the real motion vector is directly injected on the input of the compensation module.
• the system comprises means for transmitting only the macroblocks not belonging to said displaced zone to said motion vector estimation module; a subtracter for effecting the difference between the pixels of the current image and the predicted zone and providing a residual error corresponding to this difference; a frequency transform module applying a frequency transform on each macroblock processed by said estimation module as well as on said residual error; a module for quantizing data from said frequency transform module;
• an entropic coder for coding data from said quantization module.
• said video coding is a spatio-temporal coding H264 - the screen of said server is displayed by said client terminal on a screen according to a RFB protocol "Remote Frame Buffer" such as the VNC protocol "Virtual Network Computing", said real movement vector of said displaced zone is determined in the following cases: horizontal or vertical scrolling of said displaced zone with a browser-type application; o moving a graphical window of the operating system of said server; o transition from one transparency to another transparency in the case of a slide show; o Flash type animation.
• said client terminal is a video decoder;
• said current image as well as said real motion vector are initially coded in an RGB format and then undergo a transformation in a YUV format.
• a motion estimation module 105 also hereinafter referred to as a motion vector estimation module
• the reception module 101 receives as input a predictive image F n .
• F n is the current image of the entire server screen.
• the invention relates only to the coding of the predictive images, the intra-predictive coding of the images I continuing to be done according to known techniques. Thus, to make the diagram clearer, the means necessary for intra-predictive coding have been deliberately omitted.
• the reception module 101 also receives as input information on the zones having undergone a displacement (also called zone displaced in the remainder of the description) in the image F n .
• the displaced zone is a rectangular zone generally represented by a quadruplet (x, y, I, h): x and y represent respectively the abscissa and the ordinate of the point at the top left of the zone, I represents the width of the rectangle and h is the height of said rectangle.
• this real vector can be obtained by the server via the programming interfaces of its graphical environment, also called API (Application Programming Interface) for graphical user interface (GUI "Graphical User Interface") of the software application running on the server and used by the client terminal or operating system (or “operating system” in English) of the server, Windows TM for example.
• API Application Programming Interface
• GUI graphical user interface
• This real motion vector is known to the software application since the latter is at the initiative of the displacement of the area following an event (typically an event generated by a click or mouse movement or typing) of the user final via the client terminal.
• an event typically an event generated by a click or mouse movement or typing
• the size of the rectangle can also be obtained by functions of the "Windows" type. innerHeight "and” Windows. innerWidth ".
• the server can obtain values characterizing the real movement vector of the zone moved by the user via the client terminal.
• the motion vector m (mx, my) ⁇ coded in RGB format is also transformed into YUV12 format.
• the input data processing module 102 comprises:
• each current image F n to be encoded is divided by means 103 into macroblocks corresponding to a rectangular elementary region of the image having a variable size between 4x4 and 16x16 pixels (via 8x16, 8x8, ).
• the means 104 knowing the displaced areas of the image F n as well as their real motion vectors make it possible to attribute to the macroblocks belonging to a displaced zone the same real motion vector. Therefore, the means 1 19 will guide only the macroblocks not affected by a zone moved to the motion estimation module 105, the actual motion vectors of the other macroblocks being transmitted directly to the motion compensation module 106 via the means 118.
• the function of the motion estimation module 105 is to retrieve a macroblock of the current image F n in at least one previous image F n- i of the server screen in its entirety (it could also be a posterior image in the case of an image B and even a plurality of images before and / or after).
• a motion vector which corresponds to the difference between the position of the selected region and that of the selected region. macroblock.
• the motion vectors that have been retained by the estimation module (in addition to the real motion vectors transmitted by the means 1 18) are transmitted to the motion compensation module 106. This gives a prediction error due to the fact that the region retained in the past image is not exactly equal to the macroblock analyzed.
• a predicted picture P is obtained.
• Subtractor 109 then calculates a residual error D n between the pixels of F n and the predicted picture P.
• a frequency transform (of discrete cosine transform type DCT "Discrete Cosine Transform” or Hadamard transform) is applied via the frequency transform module 1 12 on each macroblock that has undergone motion estimation, as well as on the residual error D n .
• This transform makes it possible to have a frequency representation of the modified zones.
• the data from the frequency transform module 1 12 are then quantized (ie coded on a limited number of bits) by the quantization module 1 13 to provide transformed and quantized parameters X.
• the function of the quantization module 1 13 is to define different quantification steps depending on whether certain components will be judged or not significant visually; these quantization steps are defined in a quantization step table.
• the module 1 14 of inverse quantizing retrieves the processed and quantized parameters X which then pass through the module 115 of inverse frequency transform that operates an inverse frequency transform to recover a quantized version D 'n of the residual error D n; this quantized version D ' n is then added to the macroblocks of the predicted zone P by the adder 1 10; the image at the output of the adder 1 10 is then processed by the deblocking filter to provide a reconstructed image F ' n corresponding to a set of reconstructed zones having the same position, the same width and the same height as the modified areas.
• F ' n is used internally by the decoder 100 to estimate the quality of the encoding.
• the quantized results X from the quantization module 1 13 are then reordered by the reordering module 108 to group together the non-zero coefficients so as to allow an efficient representation of the other coefficients having a zero value.
• the data then undergoes a final phase of entropy coding compression via the entropy coder 120.
• the function of the encodes encoder is to re-encode the data differently in order to reduce the number of bits necessary for their encoding by approaching as close as possible to the minimum of theoretical bits (which is fixed by entropy).
• the entropy encoder 120 constructs an output stream ⁇ in a Network Abstraction Layer (NAL) format defined to allow the use of the same video syntax in many network environments.
• NAL Network Abstraction Layer
• the invention is not limited to the embodiment just described.
• the invention has been more particularly described in the context of the H264 coding but it applies to any type of spatiotemporal coding: this is for example the case of MPEG2 coding or VC1 coding. (SMPTE video compression standard "Society of Motion Picture and Television Engineers").
• motion vector has been described as a two-dimensional vector but it is also possible to use a three-dimensional motion vector, for example in the case of a graphical interface such as Aero TM which is the graphical interface of Windows Vista TM for displaying 3D effects.

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

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• 2008
  • 2008-12-30 FR FR0859113A patent/FR2940736B1/fr not_active Expired - Fee Related
• 2009
  • 2009-11-16 CN CN200980156608.0A patent/CN102318344B/zh not_active Expired - Fee Related
  • 2009-11-16 US US13/142,551 patent/US8731060B2/en not_active Expired - Fee Related
  • 2009-11-16 EP EP09768199A patent/EP2380350A1/fr not_active Withdrawn
  • 2009-11-16 BR BRPI0923824-7A patent/BRPI0923824A2/pt not_active Application Discontinuation
  • 2009-11-16 WO PCT/FR2009/052193 patent/WO2010076439A1/fr active Application Filing

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