Streaming Audio and Video

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Streaming Audio and Video
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Problems with Delivering Audio, Video and
Animations over the WEB

• File sizes large, perhaps infinite for live
  webcasts
• Cant wait for file to completely download
• WEB bandwidth unreliable - high variance
• Bandwidth varies from minute to minute
• Need to have complex compression and streaming
  protocols to compensate
• Not supported by HTTP protocol

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Current Solutions

• Real Networks
• RTSP - Real Time Streaming Protocol
• Needs a separate server
• Protocol supports multiple, simultaneous streams
  (audio, video, animation, text)
• Helper App to play the streams (REAL PLAYER G2)
• SMIL language to describe relationship between
  streams
• Automatic, dynamic bandwidth negotiation

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Other Solutions

• Microsoft ASF - Advanced Streaming Format
• Only supports one stream, need 3rd party tools to
  combine multiple streams into ASF format
• Works with Microsoft NETSHOW
• Supports multiple bitrates in one stream
• includes high bandwidth intranet option

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Publishing Streaming Media with Real Networks

• Need 3 components
• WEB Server
• Create links to .RAM, or .SMI files
• RAM files point to REAL Networks server
• Real Networks Server
• Files are housed here
• Special Streaming support
• Multicast support
• Handles Live Streams
• Browser Helper APP
• Real Player G2 - can run standalone

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Example ..

• First, need to capture and encode Video/audio in
  G2 Format
• Run Encoder software
• Specify audio and video codecs to use
• Each bitrate has a different codec
• Can use multiple bitrates
• Move Encoded file to Real Networks Server
• Create Links on WEB server to point to file

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Video file TEST.RM

• Create link to .ram file on WEB server
• Click here to see video
• Create TEST.ram file
• rtsp//videos.stern.nyu.edu554/TEST.rm

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What Happens

• User clicks on link
• Link is a .ram file, so helper app is invoked to
  process the file
• Helper App (REAL PLAYER G2) starts and is passed
  the 1 line file by the web server
• REAL PLAYER G2 reads filename and then connects
  to the video server
• Video Server and G2 now have a separate TCP/IP
  connection (port 554) to communicate over

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Synchronized Media

• What happens if I want to synchronize several
  different streams. Need to use SMIL
• The link needs to point to a .SMI file instead of
  a RAM file.
• Simple example, put an intro in front of the
  video
• I.e. play intro file followed by TEST.rm

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SMIL Example

• 
  first file to play
• 
  second file to play

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More Advanced SMIL

• Smil can also play material in parallel in
  different windows
• Example would be a REAL TEXT presentation in one
  window, with synchronized Real pics in another
  window, and synchronized audio playing as the
  slides (and text) changes.
• Real Presenter Real Networks add-on (29.95) to
  Powerpoint to allow streaming powerpoint
  narration.