RTP support for Theora/Vorbis and multicasting

Update on current state-of-the-art:

  • Fluendo supported a draft specification of Theora and Vorbis RTP encapsulation and gstreamer has implementation for both Theora and Vorbis
  • Implementation issues: based on Fluendo sponsored drafts and use of such RTP libraries like librtp it is relatively simple to implement Theora and Vorbis RTP encapsulation
  • the support for lossy transport (such as RTP/UDP) should also have support in the codec, unfortunately neither vorbis nor theora does not support packet losses and cannot easily recover from missing data
  • there are different approaches with implementation of compensation for lost data. In term of support in existing codecs, MPEG-2 codecs can deal with lost blocks, but newer ones such as MPEG-4 and H.264 deal really badly with lost data
  • possible problems with implementation of transport over RTP on client and server side:
    • timeline reconstruction on the client side (time synchronisation between server and client required, otherwise timeline can be reconstructed using for instance linear regression)
    • RTP over HTTP is a very problematic and results poor performance
  • no specificationon of Diract encapsulation in RTP payload
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