Published on October 30, 2007
Author: sudarsun
Source: slideshare.net
Audio and Video over Internet Sudarsun S., M.Tech Checktronix India Pvt Ltd Chennai 600034 [email_address]
Introduction What is Audio/Video over Internet? What are the benefits of AV on Internet? Cost of traditional communication Availability/Mobility with Wireless Entertainment Industry On demand Movie, Songs Duplication Protection Distance does not matter! Decentralization What is and Why Streaming data? Real-time Communication Protocols
What is Audio/Video over Internet?
What are the benefits of AV on Internet?
Cost of traditional communication
Availability/Mobility with Wireless
Entertainment Industry
On demand Movie, Songs
Duplication Protection
Distance does not matter!
Decentralization
What is and Why Streaming data?
Real-time Communication Protocols
Agenda Learn the fundamentals of streaming TCP, UDP and their limitations RTP, RTSP to overcome TCP limitations Error Correction and Detection Low Quality Piggybacking Interleaving Understand “On demand” multimedia data On demand cinema Video conferencing
Learn the fundamentals of streaming
TCP, UDP and their limitations
RTP, RTSP to overcome TCP limitations
Error Correction and Detection
Low Quality Piggybacking
Interleaving
Understand “On demand” multimedia data
On demand cinema
Video conferencing
Overview The big picture
The big picture
Media Data types Audio : WAV, MP3, RM Video: AVI, MPG, MOV, RM Bandwidth calculation 3GPP, 3GPP2 3rd generation, high-speed wireless networks MPEG4 Professional-quality audio and video streams H264 formats MPEG-4 standard (Part 10) used across 3G for mobile devices to iChat AV for video conferencing to HD for broadcast and DVD
Audio : WAV, MP3, RM
Video: AVI, MPG, MOV, RM
Bandwidth calculation
3GPP, 3GPP2
3rd generation, high-speed wireless networks
MPEG4
Professional-quality audio and video streams
H264 formats
MPEG-4 standard (Part 10) used across 3G for mobile devices to iChat AV for video conferencing to HD for broadcast and DVD
TCP & UDP Connection Oriented – Is that a Overhead ? Connectionless – Will that guarantee timely delivery? Maximum Effort Reliability vs Just In Time with permissible error rate Packet Sequence – Is that an Advantage ? Summary of general deficiencies
Connection Oriented – Is that a Overhead ?
Connectionless – Will that guarantee timely delivery?
Maximum Effort Reliability vs Just In Time with permissible error rate
Packet Sequence – Is that an Advantage ?
Summary of general deficiencies
RTP (RFC 3550) Real-time Transport Protocol on UDP Uses RTCP (special set of messages) to exchange periodic reports One RTP session per media flow 16 bit sequence numbers to detect packet loss 32 bit time stamp to handle jitter due to network
Real-time Transport Protocol on UDP
Uses RTCP (special set of messages) to exchange periodic reports
One RTP session per media flow
16 bit sequence numbers to detect packet loss
32 bit time stamp to handle jitter due to network
RTP Format (V) Version; 2 bits (P) Padding; 1 bit. (X) Extension; 1 bit. (CC) CSRC Count; 4 bits. (M) Marker; 1 bit. (PT) Payload Type; 7 bits. Sequence Number ; 16 bits. Time Stamp ; 32 bits. SyncSRCId ; 32 bits. ContributingSRCId List ;
How RTP Works? IP UDP RTP HDR Audio Payload IP UDP RTP HDR Video Payload Uses separate sessions for audio and video Uses sequence number to synchronize audio/video
Uses separate sessions for audio and video
Uses sequence number to synchronize audio/video
RTP Vs OSI Data Link Frame Relay Ethernet Network IP IP UDP UDP Transport RTP RTP Application MPEG2 video PCMA audio
RTCP Supervise QoS Reception reports, Sender reports, Source description Reports: packets sent/lost, inter-arrival jitter Helps modify sender transmission rate and for diagnostics purpose RTCP bandwidth = 5% of session BW Commands: SR, RR, SrcDESc, BYE, APP
Supervise QoS
Reception reports, Sender reports, Source description
Reports: packets sent/lost, inter-arrival jitter
Helps modify sender transmission rate and for diagnostics purpose
RTCP bandwidth = 5% of session BW
Commands: SR, RR, SrcDESc, BYE, APP
Continuous Media Real-time (Video Conferences) Interactive Tight timing relationship Error rate/Jitter to be near Zero Streaming Playback stored media Error rate need not be very low Loose timing relationship
Real-time (Video Conferences)
Interactive
Tight timing relationship
Error rate/Jitter to be near Zero
Streaming
Playback stored media
Error rate need not be very low
Loose timing relationship
RTSP (RFC 2326) Application-level protocol for control over the delivery of data with real-time properties. Works on top of HTTP Extensible framework to enable controlled, on-demand delivery of real-time data. Supports live data feeds and stored clips Controls multiple data delivery sessions (UDP, multicast UDP, TCP). Delivery mechanisms based on RTP.
Application-level protocol for control over the delivery of data with real-time properties.
Works on top of HTTP
Extensible framework to enable controlled, on-demand delivery of real-time data.
Supports live data feeds and stored clips
Controls multiple data delivery sessions (UDP, multicast UDP, TCP).
Delivery mechanisms based on RTP.
RTSP Methods OPTIONS- obtain available methods SETUP- Establish transport ANNOUNCE- alter description of media object. DESCRIBE- get low level description of media object. PLAY- start playback. RECORD- Start recording PAUSE- suspend delivery, keep state SET_PARAMETER- device or encoding control TEARDOWN- remove state.
OPTIONS- obtain available methods
SETUP- Establish transport
ANNOUNCE- alter description of media object.
DESCRIBE- get low level description of media object.
PLAY- start playback.
RECORD- Start recording
PAUSE- suspend delivery, keep state
SET_PARAMETER- device or encoding control
TEARDOWN- remove state.
Error Correction Piggy backing (FEC) Interleaving Combine both
Piggy backing (FEC)
Interleaving
Combine both
Low Quality Piggybacking Works for single packet loss, How about multi-packet loss ?
Interleaving Data blackout is recovered with intermittent jitter
Network Strategies Multicasting reduces amount of redundant data transferred Streaming media delivery networks allow for multiple, geographically scattered servers (achieved either by splitting or caching ) Dedicated networks guarantee bandwidth Multiple-access transmissions over Internet—requested info sent from several different locations simultaneously
Multicasting reduces amount of redundant data transferred
Streaming media delivery networks allow for multiple, geographically scattered servers (achieved either by splitting or caching )
Dedicated networks guarantee bandwidth
Multiple-access transmissions over Internet—requested info sent from several different locations simultaneously
Streaming Media Three modes in which video information can be streamed: Live broadcasting On-demand streaming Conferencing
Three modes in which video information can be streamed:
Live broadcasting
On-demand streaming
Conferencing
Live Broadcasting System SLTA: Simulated Live Transfer Agent (Rebroadcasting)
On-demand System Structure
Streaming Media – On demand Distribution system similar to live broadcasting system, except: No direct connection between encoder and server Remote proxy servers can cache popular files Clients allowed to rewind, fast forward, etc. Server proxy transfers only initiated by client
Distribution system similar to live broadcasting system, except:
No direct connection between encoder and server
Remote proxy servers can cache popular files
Clients allowed to rewind, fast forward, etc.
Server proxy transfers only initiated by client
Where to Get More Information http://www.mediacollege.com/video/streaming/overview.html http://www.apple.com/quicktime/technologies/ http://www.teamsolutions.co.uk/streaming.html http://archive.dstc.edu.au/RDU/staff/jane-hunter/video-streaming.html http://www2.umist.ac.uk/isd/lwt/clickgo/the_guide/the_guide.htm http://emoney.al.ru/capture-streaming-video-and-audio/ http://www.cit.cornell.edu/atc/itsupport/streaming.shtml http://www.yolinux.com/TUTORIALS/LinuxTutorialRealVideoStreaming.html http://nms.csail.mit.edu/projects/oxygentv/
http://www.mediacollege.com/video/streaming/overview.html
http://www.apple.com/quicktime/technologies/
http://www.teamsolutions.co.uk/streaming.html
http://archive.dstc.edu.au/RDU/staff/jane-hunter/video-streaming.html
http://www2.umist.ac.uk/isd/lwt/clickgo/the_guide/the_guide.htm
http://emoney.al.ru/capture-streaming-video-and-audio/
http://www.cit.cornell.edu/atc/itsupport/streaming.shtml
http://www.yolinux.com/TUTORIALS/LinuxTutorialRealVideoStreaming.html
http://nms.csail.mit.edu/projects/oxygentv/
Limitations Bandwidth limitation Congestion and Quality of network Buffer Overhead in Portable devices Compression and Decompression overhead Security issues Eavesdropping Duplication by Data Augmentation
Bandwidth limitation
Congestion and Quality of network
Buffer Overhead in Portable devices
Compression and Decompression overhead
Security issues
Eavesdropping
Duplication by Data Augmentation
Some Servers Audio Winamp’s Shoutcast Server Streamsicle Broadcast server RealMedia Stream server Video Quicktime Server Helix universal server Macromedia communication server Ffmpeg ( http:// sourceforge .net/projects/ ffmpeg / )
Audio
Winamp’s Shoutcast Server
Streamsicle Broadcast server
RealMedia Stream server
Video
Quicktime Server
Helix universal server
Macromedia communication server
Ffmpeg ( http:// sourceforge .net/projects/ ffmpeg / )
Conclusion Streaming multimedia poses many challenges to video encoders Variability of channel performance High server workloads Need to adapt coded bit rate to match channel capacities; must be done efficiently and on the fly
Streaming multimedia poses many challenges to video encoders
Variability of channel performance
High server workloads
Need to adapt coded bit rate to match channel capacities; must be done efficiently and on the fly
Thank You Sudarsun S., M.Tech Director – Research and Development Checktronix India Pvt Ltd [email_address] November 2005
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