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Streaming Audio and Video

Streaming Audio and Video. 60-520 Seminar Topic Instructor: Dr. A. K. Aggarwal Presented By Mostafa Monwar. What is Streaming Technology. A technique for transferring data such that it can be processed

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Streaming Audio and Video

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  1. Streaming Audio and Video 60-520 Seminar Topic Instructor: Dr. A. K. Aggarwal Presented By Mostafa Monwar

  2. What is Streaming Technology A technique for transferring data such that it can be processed as a steady and continuous stream, client does not have to download the entire file to view it. Data Source Network The portion in the buffer The portion client is viewing

  3. Advantages • It reduces download time • It provides steady service • Slower systems can take advantage of streaming technology • Provide service on demand Applications are utilizing this technology are: Streaming Video, IP telephony, Internet Radio, Distance learning, Videoconferencing, Interactive games and so on

  4. Disadvantages • It is difficult to keep the service steady if the bandwidth is low • The maintenance of streaming server is relatively expensive • Packet loss may occur during the transmission

  5. 3 types of delivery methods of streaming media • Streaming Stored Audio and Video • Streaming Live Audio and Video • Real-Time Interactive Audio and Video

  6. Media Player or Helper Application Three main streaming media companies or products are: RealPlayer (RealNetworks), Media Player (Microsoft) and QuickTime (Apple). • Three basic tasks of media players: • Decompression • Jitter Removal • Error Correction

  7. Accessing Audio & Video thru a Web server Web Browser HTTP Web Server With Audio Files Client Files Media Player

  8. Accessing Audio & Video thru a Meta File Web Browser HTTP request /response Client for meta file Web Server meta file HTTP Media Player Audio/Video file requested and sent using HTTP A meta file contains information of URL, type of encoding, etc about the audio/video file that is to be streamed.

  9. RTSP Diagram Web Browser HTTP request/response Client Web Server meta file RTSP Streaming Command Media Player Streaming Server RTP Audio / Video Content HTTP is insufficient for user interaction. With streaming server audio/video file can be sent over UDP,

  10. Protocols • RTSP: Real Time Streaming Protocol • RTP : Real-time transfer Protocol

  11. RTSP • RTSP is a industry standard Internet application level protocol • RTSP is a framework for delivering and transmission of multicast data stream • RTSP is a protocol that allows a media player to control the transmission of a media stream for exchanging control information

  12. RTSP Message Format Start Line Message Header …… Message Header CRLF [message body] Request-Line Method SP Request-URI SP RTSP-Version CRLF Status-Line RTSP-Version SP Status Code SP Reason Phrase CRLF Header Field-name : field-value CRLF

  13. RTSP Features • RTSP works in the conjunction with RTP to deliver streaming audio & video content • RTSP maintains a server state during transmission unlike HTTP • Client-Server architecture • Overcome the limitations of HTTP. RTSP enhance HTTP functions • RTSP provides the synchronization of events

  14. RTP • RTP is used to transmit real-time data • RTP encapsulate segments Payload Sequence Timestamp Synchronization Misc type number source identifier

  15. RTSP Operation HTTP GET Web Server Web Browser HTTP Presentation Description File Setup Play Media Player Media Player Media Stream RTSP Pause Teardown

  16. Presentation Description File <title> Music </title> <session> <group language=en lipsync> <switch> <track type=audio e=”PCMU/8000/1” src=”rtsp://audio.com/music/audio.en/lofi”> <track type=audio e=”DV14/16000/2” pt=”90 DV14/8000/1” src=”rtsp://audio.com/music/audio.en/hifi”> </switch> <track type=”video/jpeg” src=”rtsp://video.com/music/video”> </group> </session>

  17. Fixed Playout Delay Playout Schedule p-r Missed playout Packets generated Packet received Playout Schedule p`-r r p p`

  18. Forward Error Correction 1 2 3 4 Original stream 1 1 2 2 3 3 4 Redundancy Internet 1 3 4 1 LOSS Received stream 2 4 1 2 3 Reconstructed stream

  19. Interleaving Original Stream 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1 5 9 13 2 6 10 14 3 7 11 15 4 8 12 16 Interleaved Stream Received Stream 1 5 9 13 2 6 10 14 LOSS 4 8 12 16 1 2 4 5 6 8 9 10 12 13 14 16 Reconstructed Stream

  20. References http://www.rtsp.org/ http://www.cs.helsinki.fi/u/jmanner/Courses/seminar_papers/rtsp.pdf http://www.javvin.com/protocol/rfc2326.pdf http://www.cs.columbia.edu/~hgs/rtp/ James F. Kurose, Keith W. Ross. Computer Networking, 2nd Edition, Addison Wesley Longman, Inc, 2003. http://www.webopedia.com/TERM/R/RTSP.html

  21. Any Questions

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