Networks & Multimedia

Amit Pande,Post-doctoral fellow,Department of Computer Science,University of California Daviswww.cs.ucdavis.edu/~amit

Material adapted from Internet sources, CS529 course at WPI

Presentation Outline Evolution of wireless and Cellular

Networks, mobile phones, evolution of Multimedia coding

Multimedia services over Internet

Going back – 15 years Landline phonesAnalog camcordersCRT TV

Network – the backbone infrastructure

Cellular networks

EDGE MCS-1 59.2 Kbps

Evolved Edge 1000 Kbps

HSCPA 14 Mbps (download)

HSPA+ (release 9)

84 Mbps(download)

LTE >100 Mbps (download)>50 Mbps (upload)

Low latency

LTE advanced 1 Gbps

The traditional sense of watching TV channels or playing a video CD are soon disappearing.

GoogleTV has integrated www and search tools to HDTV

• Pico-projectors can project HD video from mobile devices

Frequency Transform

Motion compensa-

tion

Entropy coding

Frequency Transform

Motion compensa-

tion

Entropy coding

50 Kbps

50 Mbps

Network Traffic Today Internet dominated by text-based

applications Email, FTP, Web Browsing

Very sensitive to loss Example: lose a byte in abcd.exe program and

it crashes!Not very sensitive to delay

10’s of seconds ok for Web page download Minutes for file transfer Hours for email to delivery

Multimedia on the Internet

Multimedia not as sensitive to loss Words from speech lost still ok Frames in video missing still ok

Multimedia can be very sensitive to delay Interactive session needs one-way delays

less than ½ second!New phenomenon is effects of

variation in delay, called jitter!

Jitter

Jitter-Free

Video Coding MPEG -1 352x240 at 30 frames per

second (fps) MPEG -2 1280x720 at 60 fps. CD

quality MPEG -4 objects, low bit-rates

H264 SVC Parts of the video bit stream can be removed so that

the remaining substream can still be decoded Single-layer vs. Base layer + Enhancement layers

Benefits in a mobile environment Heterogeneous clients Improved error resiliency

Classes of Internet Multimedia AppsStreaming stored mediaStreaming live mediaReal-time interactive media

Streaming Stored Media Stored on server 1-way communication, unicast Examples: pre-recorded songs, famous

lectures, video-on-demand, YouTube RealPlayer, Media Player, Quicktime, FLV Interactivity, includes pause, ff, rewind… Delays of 1 to 10 seconds or so tolerable Need reliable estimate of bandwidth Not very sensitive to jitter

Streaming Live Media “Captured” from live camera, radio, T.V. 1-way communication, maybe multicast Examples: concerts, radio broadcasts, lectures,

IPTV Can use: RealPlayer, Media Player… but often

custom Limited interactivity… Limited opportunities for compression, scaling Delays of 1 to 10 seconds or so tolerable Need reliable estimate of bandwidth Not so sensitive to jitter

Streaming Interactive Media

“Captured” from live camera, microphone 2-way communication Examples: VoIP, video conference Very sensitive to delay

< 150 ms one-way delay good< 400 ms ok> 400 ms crappy

Sensitive to jitter

TCP or UDP? Above IP we have UDP and TCP as the

de-facto transport protocols. Which to use?

TCP or UDP? TCP

+ In order, reliable (no need to control loss)- Congestion control (hard to pick encoding level right)

UDP - Unreliable (need to control loss)+ Bandwidth control (easier to control

sending rate)

Thank youQuestions?

Feedback/Comments:amit@cs.ucdavis.edu