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H.263 의 구현

H.263 의 구현. 서울대학교 컴퓨터 공학과 CAP 연구실 오현옥 , 오문욱. Introduction. Video coding for low bitrate communication. Brief Specification. Video input and output. Source coding algorithm. Half pixel precision is used for the motion compensation 4 negotiable coding options.

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H.263 의 구현

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  1. H.263의 구현 서울대학교 컴퓨터 공학과 CAP연구실 오현옥, 오문욱

  2. Introduction • Video coding for low bitrate communication

  3. Brief Specification

  4. Video input and output

  5. Source coding algorithm • Half pixel precision is used for the motion compensation • 4 negotiable coding options

  6. 4 negotiable coding options • Unrestricted Motion Vector mode • motion vectors are allowed to point outside the picture • movement across the edges of the picture for the smaller picture • useful in case of camera movement • Syntax-based Arithmetic Coding mode • arithmetic coding is used instead of variable length coding • SNR and reconstructed pictures will be the same • Advanced Prediction mode • Four 8x8 vectors instead of one 16x16 vector are used • PB-frames mode • come from H.262 where there are P, B

  7. Sampling

  8. Source coder

  9. Top schematic

  10. TransGal

  11. MBEncode

  12. InvTransGal

  13. MBDecode

  14. Interpolate

  15. Simulation • Motion Estimation 부분에서 많은 시간 소요 • 이유 : full search scheme • 방법 • hierarchy search 기법의 이용 • 전용 프로세서에서 처리 • Framework자체의 overhead • code generation

  16. Rate control experiment • set0 : PSNR set1 : QP set2 : number of bits • IPPIPP… and < 40 Kbits/sec, 10frames/sec • below 30dB

  17. set0 : PSNR set1 : QP set2 : number of bits • IPPPPPIPP… and < 40 Kbits/sec • 30dB ~ 40dB

  18. set0 : PSNR set1 : QP set2 : number of bits • IPPPPPPPPIPP… and < 40 Kbits/sec • upper 35dB

  19. set0 : PSNR set1 : QP set2 : number of bits • IPPPPPPPPPPPIPP… and < 40 Kbits/sec • about 40dB

  20. 실험결과 • 비트율이 40Kbits/sec이하가 되도록 조절 • 초당 10frame을 전송 • IPPPPPPPPIPP…인 경우에 만족할 만한 화질을 보임

  21. Conclusion • H.263 encoder를 ptolemy상의 SDF domain상에서 기술 • simulation 결과 잘 동작함을 검증 • Rate control 정책을 사용하여 초당 10frame을 40Kbits/sec이하로 압축하는 경우 intra frame coding과 8개의 inter frame으로 GOP를 구성하는 것이 이상적임

  22. 분담내역 • 분담내역 • 오 현 옥 • 전체 스키메틱 • 각 block들의 코드 기술 • 전체 시뮬레이션 • 오 문 욱 • Motion Estimation block • H/W 합성을 위한 prototyping board test 및 debugging

  23. 참고문헌 • “VIDEO CODING FOR LOW BITRATE COMMUNICATION”, ITU-T DRAFT H.263 ( 2 May, 1996 ) • Telenor ( http://www.telenor.no ) • Ptolemy( http://ptolemy.eecs.berkeley.edu )

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