1 / 31

Streaming Media

Streaming Media. Daniel Johnson. What is it?. What is it?. Playing a media file stored on a remote server on a local client. Examples. iTunes “Shared Libraries” Google Video, youTube, etc. How does it work?. How does it work?. True Streaming Progressive Streaming or Pseudo-streaming.

dane-hodges
Download Presentation

Streaming Media

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Streaming Media Daniel Johnson

  2. What is it?

  3. What is it? Playing a media file stored on a remote server on a local client

  4. Examples • iTunes “Shared Libraries” • Google Video, youTube, etc.

  5. How does it work?

  6. How does it work? • True Streaming • Progressive Streaming or Pseudo-streaming

  7. True Streaming • Benefits • Counter piracy • Files stay on the server • No need for DRM • You can start playing anywhere in the file

  8. True Streaming • Costs • Expensive • Requires a “streaming server” • Poor quality • Delay • Jitter • Low resolution

  9. True Streaming • Protocols • RTP – Real-time Transport Protocol • RTCP - Real-time Transport Control Protocol • RTSP – Real-Time Streaming Protocol (All of the above come in a Secure variety) • RDT – Real Data Transport (proprietary – Real Networks) • DAAP – Digital Audio Access Protocol (proprietary – Apple Inc.) • SCTP – Stream Control Transport Protocol

  10. True Streaming - RTP

  11. True Streaming – RTCP “Control” is a bit of a misnomer: • Doesn’t actually control the stream • Used to gather data about the RTP stream • bytes sent • packets sent • lost packets • Jitter • Feedback • Round trip delay • Data can be used by apps to control flow and achieve a better, more consistent stream

  12. True Streaming - RTSP • Similar to HTTP, but with modified/additional commands to facilitate streaming media • Built to be Transport layer independent: • TCP • UDP • SCTP • RTP (most common) • Header is similar to HTTP/1.1

  13. True Streaming - RDT

  14. True Streaming – DAAP • Most widely used true streaming protocol because of the popularity of iTunes • Created by Apple as a proprietary protocol – introduced with iTunes 4 • Reverse engineered and became open source • Apple reasserts ownership with v. 7 • Poorly documented

  15. True Streaming - SCTP • Referred to as “multi-streaming” • Based on the PSTN message delivery concept • Allows multiple source and destination hosts • Keeps much of the reliability of TCP, without the restrictions because it’s basic unit is a full message instead of a byte

  16. True Streaming – SCTP

  17. Progressive Streaming • Benefits • Cheap • Built on existing internet technology • Uses standard web server • No new protocol implementations required • Much better quality (potentially)

  18. Progressive Streaming • Costs • File must be downloaded to client HDD (easy to pirate) • Can’t (technically) navigate file

  19. Progressive Streaming • Uses HTTP (sometimes FTP) to send file to client HDD • Most clients begin playing the file before the get all of it • Speeds up playback • If there’s a problem, playback stops completely • Speed is determined by total size of file • Better quality requires waiting longer, and visa versa

  20. Review True Streaming Progressive Streaming • Expensive – requires a special server • Fast • Controllable • Protected • Cheap – don’t need anything new • Slow(er) • Must start from the beginning • Open

  21. Examples • iTunes “Shared Libraries” • Google Video, youTube, etc.

  22. What about making movies?

  23. Making Movies • The right compression (codecs) • The right resolution

  24. codecs • Not all codecs work for streaming • Streaming codecs should allow • high compression • playback of incomplete files Example: MPEG-1

  25. Optimal Resolution

  26. Brief History – the Stretch • Originally video decoding was done with special hardware based on TV decoding • Rectangular pixels • Cropped the sides • Result was an optimal resolution of 352x240 • Software decoders didn’t bother with this

  27. Brief History – the Stretch The Result

  28. Brief History – the Squish • The other predominant influence on internet video was video conferencing Goals: • conserve bandwidth • Still look good • The result was settling on 176x144 • Most software decoders don’t worry about this either

  29. Brief History – the Squish The Result

  30. Effect of Streaming • Most software decoders ignore the “format” flag in the encoding • A lot of encoders had either the TV format or the video conferencing format as their default resolution (this has mostly been corrected) • Lots of videos made early on were stretched or squished

  31. Conclusion I do not like it on ABC,I do not like it on MTV. I would not, could not on CNN, I would not, could not on ESPN. It can't be 176x144, Bill G. Because then it isn't 4:3!* Use a 4:3 Aspect ratio for you web videos!

More Related