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11/11/2004

MPEG4 Codec for Access Grids National Center for High Performance Computing Speaker: Barz Hsu Email: barz@nchc.org.tw. 11/11/2004. Outline. Definition of HDTV Brief Introduction to MPEG-4 Standard History and Problems of VIC Contributions. What’s High Definition Video?.

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11/11/2004

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  1. MPEG4 Codec for Access Grids National Center for High Performance Computing Speaker: Barz Hsu Email: barz@nchc.org.tw 11/11/2004

  2. Outline • Definition of HDTV • Brief Introduction to MPEG-4 Standard • History and Problems of VIC • Contributions

  3. What’s High Definition Video? • Frame Resolution: >= 720x480 or 640x480 • Frame Rate >= 20 fps • Peak Signal to Noise Ratio (PSNR) >= 30 dB

  4. Another Key Factors for Access Grids • Real-Time • Minimize latency & jitter • Error Resilience • RTP over UDP is unreliable • Large Scale Video Conferencing • Selection of suitable coding tools • Optimization • Adaptive • network bandwidth • computing resources

  5. Status of MPEG4 • Part 2: Advanced Simple Profile (ASP) • Part 10: Advanced Video Coding (AVC or H.264) • Match MPEG-2 quality at up to half data rate • Deliver excellent video quality across entire bandwidth spectrum – from 3G to HD • (from 40Kbps to 10MBps)

  6. Performance Comparison

  7. Interoperability Issues • Communicate with Polycom, iChat AV (Tiger) • Transport Stream • RFC 3016: RTP Payload Format for MPEG-4 Audio/Visual Streams. • RFC 3640: RTP Payload Format for Transport of MPEG-4 Elementary Streams • MPEG2TS

  8. VIC: Video Conferencing Tool • Developed by Network Research Group in U.C. Berkeley • Mbone Tools used by Access Grid, inSORS, and VRVS • vic for video and rat for audio • Based on RTP/RTCP to provide real-time video • Support Multicast/Unicast Protocol • Hybrid of Tcl/Tk and C++ • Supported codecs • H.261, H.263, H.263++, MJPEG, nv, and etc.

  9. The Problems of VIC • Hard to maintain • Lack of high-quality video codec • only H.261 is relative useable • Limitation on frame resolution • Only QCIF (176x144), CIF (352x288) • Limitation on viewing resolution • Lack of exhaustive optimization oncodec, render, grabber, and etc

  10. Our Goal • Broadcast in Television Quality • Leverage with Existing Open Source Resources • VLC, MPlayer, and FFmpeg • Providing “Sense of Presence” • As Real-Time As Possible • High-Definition, High Quality • Incorporate with up-to-date codecs such as MPEG2, MPEG4 (ASP), H.264 • Less Compression Artifact • Error Resilience/Concealment

  11. MPEG4 Codec • Related Open Source Project • FFmpeg, xvid, and sklmp4 • FFmpeg/libavcodec • High performance of CPU usage • Support various codec • MPEG4, MPEG2, MPEG1 • H.263++, H.263, H.261 • Provide error resilience tools • slices, data partition • Cross Platform • Linux, Windows, and Mac OS

  12. Benefits from MPEG4 codec • Support arbitrary sizes of a video stream • in contrast to H.261 • the largest size depends on your video grabber card and camera • Less obvious block artifacts

  13. MPEG4 Performance • Typical bit-rate is1Mbps • 720x480 (NTSC) with 25 frames/sec and PSNR value is about 40 dB • Consistent bit-rate • adjusting bit-rate only affects to the quality; not influence the frame-rate • Up to 40 CIF, or 10 NTSC video streams.

  14. Deinterlace • Convert interlaced video into progressive one

  15. Efficient Color Conversion • VIC didn’t give correct color representation. • Efficient Color Conversion • Grabber (YUYV) to Encoder (YUV420) • Decoder (YUV420) to Display (RGB15/RGB16/RGB24)

  16. Scaling Viewing Windows • Original VIC • only support limited sizes of viewing windows • based on unrealistic pixel replication method • NCHC-VIC • scaling viewing windows arbitrarily without too much overhead • interpolation by 9 tap FIR filter • hardware assisted by Xvideo extension in XFree86 • full screen mode

  17. Full Screen Snapshot

  18. Real-Time Video Streaming • Real-time • the compressed data are transferred at a speed that matches the coded video source rate. • Latency, Jitter • average end-to-end delay • delay variation

  19. Error Resilience • Error Progratation

  20. Error Resilience (cont’d) • Resynchronization marker • the data between the error location and the first following resynchronization marker would have to be discarded. • Data Partition • motion vectors and related syntactic elements are transmitted first, followed by syntactic elements like MB headers, motion vectors, and DCT coefficients.

  21. Minimize Latency • Multithread Encoding • Take advantage of symmetric multiple processor architecture • Pipeline the latency of transmission and encoding • SIMD Instruction Ses • Optimized by SSE2/SSE, MMX

  22. Future Work • Support H.264 codec • Support MPEG-4 High Efficient AAC (HE-AAC)

  23. Conclusion • Project Website: • http://vic.nchc.org.tw

  24. Thanks for your attendance

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