1. 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

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

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

4. Motivation 4

5. 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

6. Conventional video codec 6

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

8. 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)

9. 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

10.  Our DVC codec:  DVC transcoder 10

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

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

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

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

15. 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

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

17. 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

18. WZ coding with NDK 18

19. 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

20. 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

21. 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

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

23. 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

24. ACK at Feedback channel 24 … syndromes

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

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

27. 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

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

29. 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

30. 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

31. 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

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

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

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

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

36. 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.

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

38. 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

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

40. 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

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

42. 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

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

44. 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. 45 Thank You

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

47. 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: 123.34 sec  Motion Learning: 1.79 sec  Others: 1.80 sec 47

48. 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 2006. Channel Encoder Channel Decoder LDPC Encoder LDPC Decoder

49. 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

50. 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

51. 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

52. 52

53. 我最少需 要 48bits 的 parity bits 1584bits 48 24 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

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

55.  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

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