cis679: mpeg-2
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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 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