Complexity reduction in VP6 to H 264 transcoder using motion vector MV reuse Jay R Padia Electrical Engineering Graduate Student The University of Texas at Arlington Supervising Professor Dr K R Rao April 19 2010 Complexity reduction in VP6 to H 264 transcoder with motion vector reuse 1 Contents Introduction VP6 H 264 VP6 H 264 comparison Cascaded architecture Proposed technique Conclusions Future work May 1 2009 Algorithm for Adaptive Grid Generation and its Application 2 Transcoding Definition Conversion of video from one format to another Bitrate conversion Spatial resolution change Temporal conversion Format change April 19 2010 Complexity reduction in VP6 to H 264 transcoder with motion vector reuse 3 Why Transcoding Multimedia applications on different devices and platforms Different bitrates frame rates spatial resolution complexity Different video standards communication inter operability Application Digital TV broadcasting DVD Video Internet video streaming Video conferencing and video telephony Video over 3G wireless High definition Bluray and HD DVD April 19 2010 Bitrate 2 to 6 Mbps 10 to 20 Mbps for HD broadcast 6 to 8 Mbps 20 to 200 kbps Video standard MPEG 2 H 264 20 to 320 kbps H 261 H 263 H 263 20 to 100 kbps H 263 MPEG 4 Part 2 36 to 54 Mbps H 264 VC 1 and MPEG 2 MPEG 2 Flash Sorrension spark based on H 263 VP6 and H 264 Silverlight uses VC1 and also MPEG 4 Part 2 Complexity reduction in VP6 to H 264 transcoder with motion vector reuse 4 On2 Truemotion VP6 Developed by On2 Technologies Licensed by Adobe for Flash video in 2005 Fundamentals YUV 4 2 0 input MB 16x16 based coding 8x8 DCT adaptive int DCT Uniform quantization pixel MV resolution MV search range max 16 pixels Reference frames previous frame and golden frame No bidirectional prediction Entropy coding Huffman and Arithmetic coding BoolCoder April 19 2010 Complexity reduction in VP6 to H 264 transcoder with motion vector reuse 5 Flash video adoption of H 264 Significance of VP6 due to Flash player outreach Flash player has wide outreach more than 90 computers Major websites Youtube Facebook Google video Yahoo video metacafe Reuters com etc A lot of streaming video content on internet in VP6 Adobe adopted H 264 for Flash video in 2007 Termed as one of the biggest thing to happen to web video May 1 2009 Algorithm for Adaptive Grid Generation and its Application 6 VP6 Block diagram Encoder April 19 2010 Decoder Complexity reduction in VP6 to H 264 transcoder with motion vector reuse 7 VP6 Golden frames Special frame buffer Holds last I frame by default Any part of the frame can be updated later I Intra frame P predicted frame April 19 2010 Complexity reduction in VP6 to H 264 transcoder with motion vector reuse 8 VP6 Golden frame Static backgrounds update the golden frame with the nonmoving background blocks background reproduced from golden frame reference A frame which references only golden frame helps in recovery in case of data loss April 19 2010 Complexity reduction in VP6 to H 264 transcoder with motion vector reuse 9 VP6 Prediction loop filter No H 264 like loop filter in the reconstruction buffer Supports filtering of pixels adjacent to 8x8 block boundaries When prediction block straddles an 8x8 block boundary 2 filter options Deblocking filter 1 3 3 1 Deringing filter Deringing and deblocking characteristics April 19 2010 Complexity reduction in VP6 to H 264 transcoder with motion vector reuse 10 VP6 DCT Modified non standard fixed point integer DCT DCT complexity adjusted as a function of target quantization Faster performance for coarser quantization To simplify the inverse DCT the zero coefficients can be clubbed together Possible using scan ordering at encoder and reordering at the decoder April 19 2010 Complexity reduction in VP6 to H 264 transcoder with motion vector reuse 11 VP6 Scan ordering Process of providing customized scanning order 8x8 block 64 coefficients 0 to 63 New ordering specified by a 64 element array Default scan order zig zag scan order figure Custom scan order Index 0 1 2 3 4 5 April 19 2010 Situation Coefficient 1 Coefficients 2 4 Coefficients 5 10 Coefficients 11 21 Coefficients 22 36 Coefficients 37 63 Complexity reduction in VP6 to H 264 transcoder with motion vector reuse 12 VP6 Custom scan ordering 8 x 8 coefficients block May 1 2009 Zig zag scan ordered Custom scan ordered 0 1 2 3 4 5 6 0 1 2 3 4 6 5 Algorithm for Adaptive Grid Generation and its Application 13 MB modes in VP6 Coding mode Prediction frame Motion vector MV CODE INTER NO MV Previous frame reconstruction Fixed 0 0 CODE INTRA None None CODE INTER PLUS MV Previous frame reconstruction Newly calculated MV CODE INTER NEAREST MV Previous frame reconstruction Same MV as Nearest block CODE INTER NEAR MV Previous frame reconstruction Same MV as Near block CODE USING GOLDEN Golden frame Fixed 0 0 CODE GOLDEN MV Golden frame Newly calculated MV CODE INTER FOURMV Previous frame reconstruction Each of the four luma blocks has associated MV CODE GOLD NEAREST MV Golden frame Same MV as Nearest block CODE GOLD NEAR MV Golden frame Same MV as Near block May 1 2009 Algorithm for Adaptive Grid Generation and its Application 14 Nearest Near blocks Nearest and Near blocks First 2 non 0 0 MVs encountered in the order as shown in the figure first Nearest second Near Undefined if no such non 0 0 MVs can be found from the first 12 blocks as shown Intra fixed DC prediction CODE INTER FOURMV all 4 luma blocks have different MVs May 1 2009 Algorithm for Adaptive Grid Generation and its Application 15 H 264 Overview Open licensed standard latest block oriented motioncompensation based codec Good video quality at substantially lower bit rates Better rate distortion performance and compression efficiency Wide variety of applications such as video broadcasting video streaming video conferencing D Cinema HDTV Adopted by Adobe for Flash video in 2007 April 19 2010 Complexity reduction in VP6 to H 264 transcoder with motion vector reuse 16 H 264 Fundamentals Uses hybrid block based video compression techniques Includes the following features Intra picture prediction 4x4 and 8x8 integer transform Multiple reference pictures Variable block sizes for ME MC Quarter pel precision for motion compensation In loop de blocking filter Improved entropy coding April 19 2010 Complexity reduction in VP6 to H 264 transcoder with motion vector reuse 17 H 264 Encoder block diagram April 19 2010 Complexity reduction in VP6 to H 264 transcoder with
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