Distributed Video System realized on mobile device with efficient Feedback channel 分散式影像編碼在手機上的實現與有效率 的回饋通道 1 Chen,chun-yuan 陳群元 Advisor:Prof. Wu,Ja-Ling 吳家麟 2012/6/6

Outline  Motivation and introduction  DVC architecture with mobile device  Propose an efficient feedback channel  Transcoding  Experiment Result  Conclusion  Future work 2

Motivation  Video communication is essential in Mobile device  Decrease the coding time and battery consuming on mobile. 3

Motivation 4

Introduction  For Mobile device video codec  Conventional video coding (ex:MPEG-4 H.264)  Heavy weight encoder, light weight decoder.  Distributed Video Coding  Light weight encoder, heavy weight decoder. 5

Conventional video codec 6

DVC to H.264 Transcoder 7 Clouding server: DVC to H.264 transcoder DVC encoder H.264 decoder

Channel Coding R Y =H (Y) Source encoder Correlation is exploited by motion estimation R Y =H (X|Y) Source encoder H (X|Y)H (Y) Distributed  Slepian-Wolf Theorem (1973) Wyner-Ziv Theorem (1976) Channel encoder Source decoder Side Information creation Channel decoder X Y Virtual channel H (X, Y)

Distributed Video Codec 9 DCT WZ Frames LDPCA Encoder Buffer LDPCA Decoder Key Frames Conventional Intraframe Encoder Conventional Intraframe Encoder SI generation& refinement DCT SI Reconstruction Mode selection CRC CRC check CRC-8 WZ bitstream Correlation Noise Modeling IDCT& Deblocking filter Decoded WZ Frames Decoded Key Frames

 Our DVC codec:  DVC transcoder 10

DVC to H.264 Transcoder 11 Clouding server: DVC to H.264 transcoder DVC encoder H.264 decoder

DVC Decoding Process  DVC Decoding without Feedback channel  Side-Information generation  LDPCA 12

DVC Decoding Process  DVC Decoding  Side-Information generation  Send-Request at Feedback channel  LDPCA 13

Outline  Motivation and introduction  DVC architecture with mobile device  Propose an efficient feedback channel  Transcoding  Experiment Result  Conclusion  Future work 14

DVC Encoder Realization  Implement DVC encoder on Mobile  Key frame encoding  WZ frame encoding  Efficient intra mode realization  Feedback channel transmission  Network connection between mobile and server  Determine payload of a packet with LDPCA protocal 15

Key frame encoding on Mobile  Previous ver. use JM9.5  Transcoder ref x.264 on PC 16

DVC Encoder Realization  Implement DVC encoder on Mobile  Key frame encoding  WZ frame encoding  Efficient intra mode realization  Feedback channel transmission  Network connection between mobile and server  Determine payload of a packet with LDPCA protocal 17

WZ coding with NDK 18

DVC Encoder Realization  Implement DVC encoder on Mobile  Key frame encoding  WZ frame encoding  Efficient intra mode realization  Feedback channel transmission  Network connection between mobile and server  Determine payload of a packet with LDPCA protocal 19

Efficient intra block coding  Previous ver. Transcoder Use JM code.  Intra block encoding consumes lots of time in encoding. 20 Clouding server: DVC to H.264 transcoder

DVC Encoder Realization  Implement DVC encoder on Mobile  Key frame encoding  WZ frame encoding  Efficient intra mode realization  Feedback channel transmission  Network connection between mobile and server  Determine payload of a packet with LDPCA protocal 21

Network connection  Create network connection to connect remote server.  TCP socket in C 22 Clouding server: DVC to H.264 transcoder

DVC Encoder Realization  Implement DVC encoder on Mobile  Key frame encoding  WZ frame encoding  Efficient intra mode realization  Feedback channel transmission  Network connection between mobile and server  Determine payload of a packet with LDPCA protocal 23

ACK at Feedback channel 24 … syndromes

Time consuming at Feedback channel  Packet header occupy large part of network bandwidth.  Network latency in communication at Feedback channel 25

Outline  Motivation and introduction  DVC architecture with mobile device  Propose an efficient feedback channel  Transcoding  Experiment Result  Conclusion  Future work 26

Efficient feedback channel  we propose two methods to decrease time consuming at feedback channel.  Estimate the syndromes size per WZ frame  Estimate the syndromes size per bitplane 27

Number of requests per bitplane per band DC AC1AC2 AC3 AC4AC5 AC6AC7AC8 AC9AC10 AC11 AC12 AC13 AC14 Bitplane Number

Estimate the syndromes size per WZ frame  Estimate syndromes size by correspond WZ frame in previous GOP  Ex. GOP 4 29 Key frame Key frame WZ frame WZ frame WZ frame First GOP Key frame Key frame WZ frame WZ frame WZ frame Second GOP

formula  (ES bt ) WZn =(S bt ) WZ(n-GOPsize)  WZn means the WZ frame’s index  n-GOPsize means the correspond WZ frame in the previous GOP.  bt is the bitplane index.  (ES bt ) WZn means the estimated syndromes bit for the bt’th bitplane of WZn frame.  (S bt ) WZ(n-GOPsize) means the syndromes

Efficient feedback channel  we propose two methods to decrease time consuming at feedback channel.  Estimate the syndromes size per WZ frame  Estimate the syndromes size per bitplane 31

Number of requests per bitplane per band DC AC1AC2 AC3 AC4AC5 AC6AC7AC8 AC9AC10 AC11 AC12 AC13 AC14 Bitplane Number

Number of requests per bitplane per band DC AC1AC2 AC3 AC4AC5 AC6AC7AC8 AC9AC10 AC11 AC12 AC13 AC14 Bitplane Number

Estimate by previous bands  1.formula  2.time ratio

Number of requests per bitplane per band DC AC1AC2 AC3 AC4AC5 AC6AC7AC8 AC9AC10 AC11 AC12 AC13 AC14 Bitplane Number

formula  (ES acn bt ) WZn = ( S dc bt-1 ) WZn  WZn means the n’th WZ frame.  acn means the n’th AC band.  bt means the bitplane index of this AC band.  Which ES acn bt mean the estimated syndrome size for the bt’th bitplane in n’th AC band.  dc means the DC band.  S dc bt-1 means the syndromes bits for bt-1’th bitplane in DC band.

Outline  Motivation and introduction  DVC architecture with mobile device  Propose an efficient feedback channel  Transcoding  Experiment Result  Conclusion  Future work 37

Transcode to mobile codec  Because DVC only encode luminance part in YUV, so we got only Y for output.  Our mobile device can only read mp4 and 3gp. Y UV R G B Frame 1 Frame 2 Frame 3 Frame4 Frame 5 Frame 6 Frame 7 Frame n.mp4

Outline  Motivation and introduction  DVC architecture with mobile device  Propose an efficient feedback channel  Transcoding  Experiment Result  Conclusion  Future work 39

Experiment Result  規格  實驗數據 :  時間 (encode&decode) 、 packet 數量 ( 傳幾次 )+  RD  使用 x264 對 quality 的影響 (intra 改 quality 應該 會變，但變快 ) 40

Outline  Motivation and introduction  DVC architecture with mobile device  Propose an efficient feedback channel  Transcoding  Experiment Result  Conclusion  Future work 41

Contribution  Realize DVC encoding part on Mobile device  Implement Feedback channel  Implement encoder’s component with x264  Propose an efficient Feedback channel  Transcode the decoded sequence to mobile codec 42

Outline  Motivation and introduction  DVC architecture with mobile device  Propose an efficient feedback channel  Transcoding  Experiment Result  Conclusion  Future work 43

Future Work  Take a more precise estimation of syndrome size.  Use motion information to estimate the syndrome size.  Build a reliable DVC codec which is loss tolerate 44

45 Thank You

To do  Real time decoder  Efficient intra coding  Print MSG on Mobile 46

DVC decoding time  Side Info Creation: 0.85 sec  Overcomplete Transform: 2.35 sec  Correlation Noise Modeling: 2.33 sec  Conditional Bit Prob Compute: 0.60 sec  Update Side Info: 7.14 sec  Ldpca Decode: sec  Motion Learning: 1.79 sec  Others: 1.80 sec 47

Distributed Video Coding D. Varodayan, A. Aaron, and B. Girod, “Rate-Adaptive Codes for Distributed Source Coding,”EURASIP Signal Processing Journal, Special Issue on Distributed Source Coding,,November Channel Encoder Channel Decoder LDPC Encoder LDPC Decoder

Distributed Video Codec 49 DCT WZ Frames Extract bit-plane bit-plane 1 LDPCA Encoder Buffer bit-plane 2 LDPCA Decoder Request bits Key Frames Conventional Intraframe Encoder Conventional Intraframe Encoder Interpolation/ Extrapolation DCT Reconstruction

Distributed Video Codec 50 DCT WZ Frames LDPCA Encoder Buffer LDPCA Decoder Request bits Key Frames Conventional Intraframe Encoder Conventional Intraframe Encoder Interpolation/ Extrapolation DCT Reconstruction

Distributed Video Codec 51 DCT WZ Frames LDPCA Encoder Buffer LDPCA Decoder Key Frames Conventional Intraframe Encoder Conventional Intraframe Encoder SI generation& refinement DCT SI Reconstruction Mode selection CRC CRC check CRC-8 WZ bitstream Correlation Noise Modeling IDCT& Deblocking filter Decoded WZ Frames Decoded Key Frames

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我最少需 要 48bits 的 parity bits 1584bits LdpcaEncode 我還需要 更多的 parity Bits… 我解完了 一個 bitplane 了 ! Buffer 依序解完 所有 bitplanes 24

DVC to H.264 Transcoder 54 Clouding server: DVC to H.264 transcoder DVC encoder H.264 decoder

 接著講 header overhead  每次都傳一點，等於傳的大部分都是 header(20Bytes)  傳輸太多次，會造成大量的 delay 55

Outline  Motivation and introduction  DVC architecture with mobile device  Propose an efficient feedback channel  Transcoding  Experiment Result  Conclusion  Future work 56