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CIS679: MPEG-2

CIS679: MPEG-2. Review of MPEG-1 MPEG-2 Multimedia and networking. Review of MPEG-1. MPEG: Motion Pictures Experts Group MPEG exploits motion prediction Successive frames may have significantly same data Apply motion prediction at the Macroblock level I, P, and B frames

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CIS679: MPEG-2

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  1. CIS679: MPEG-2 • Review of MPEG-1 • MPEG-2 • Multimedia and networking

  2. Review of MPEG-1 • MPEG: Motion Pictures Experts Group • MPEG exploits motion prediction • Successive frames may have significantly same data • Apply motion prediction at the Macroblock level • I, P, and B frames • The standard allows the use of I-frame only, I and P frames only or I-, P- and B-frames => GOP: the number of frames/pictures between successive I-frames

  3. MPEG-2 • MPEG-2 strives for a higher resolution. • MPEG-1 is near the maximum data rate of about 1.5Mbits/s. • MPEG-2 targets at 40Mbits/s => high resolution. • MPEG-2 supports four levels • Low, main, high 1440 and high • There are five profiles associated with each level • The low level of MPEG-2 is compatible with MPEG-1.

  4. Multimedia Applications • Video-on-demand • Near-video-on-demand • Travel/training videos • Interactive games • Teleconferencing • IP Telephony

  5. Multimedia Application Classes • Streaming • Clients request audio/video files from servers and pipeline reception over the network and display • Interactive: user can control operation (similar to VCR: pause, resume, fast forward, rewind, etc.) • Delay: from client request until display start can be 1 to 10 seconds

  6. Multimedia Application Classes (more) • Unidirectional Real-Time • similar to existing TV and radio stations, but delivery on the network • Non-interactive, just listen/view • Interactive Real-Time • Phone conversation or video conference • More stringent delay requirement than Streaming and Unidirectional because of real-time nature • Video: < 150 msec acceptable • Audio: < 150 msec good, <400 msec acceptable

  7. Multimedia Requirements • Guarantees • Throughput and/or delay guarantees • Audio requires loss/delay guarantees • Interactive apps. require low delay • CBR & VBR • Variable bit rate places extra burden

  8. Challenges to the Current Internet • TCP/UDP/IP suite provides best-effort, no guarantees on expectation or variance of packet delay • Streaming applications delay of 5 to 10 seconds is typical and has been acceptable, but performance deteriorate if links are congested (transoceanic) • Real-Time Interactive requirements on delay and its jitter have been satisfied by over-provisioning (providing plenty of bandwidth), what will happen when the load increases?...

  9. Challenges to the Current Internet (more) • Most router implementations use only First-Come-First-Serve (FCFS) packet processing and transmission scheduling • To mitigate impact of “best-effort” protocols, we can: • Use UDP to avoid TCP and its slow-start phase… • Buffer content at client and control playback to remedy jitter • Adapt compression level to available bandwidth

  10. Conclusion • MPEG-2 • Targets at high resolution • Profiles and levels • Compatible to MPEG-1 • Multimedia application classes • Streaming • Unidirectional real-time applications • Interactive real-time applications • Multimedia requirements • Challenges

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