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 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

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.

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

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

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

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

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?...

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

Conclusion MPEG-2 Multimedia application classes 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