[vorbis] Vorbis over RTP

[Monty]

> With multicast streaming, packets can be dropped at any time, so
> it is useful to keep each packet as autonomous as possible (each
> packet should ideally be an application data unit, or ADU, as
> Ross Finlayson did for the MP3 format - see
> http://www.ietf.org/internet-drafts/draft-ietf-avt-rtp-mp3-04.txt ).

Each Vorbis packet is currently a standalone unit.  The only thing it
needs are the additional mechanisms for ordering that RTP supplies.

> In your RTP, do you send out the comments and codebook as a separate
> packet, or as part of a data packet ? 

If so, don't mix packet data like this.

> Can these change in mid-stream ?

No.  Or, rather, not in a logical stream.  When one logical stream
ends and the next begins in a physical stream, the headers might
change.  That's what streams and headers are all serialnumbered (I
seem to recall RTP providing something similar; if not, this must be
added to the payload.

> It would also be nice if each packet was kept under 576 bytes (or
> at least 1500 bytes) in size, including the IP/UDP/RTP headers,
> to avoid fragmentation. Do you worry about packet sizes in your
> implementation ?

The encoder should currently keep packet sizes low, but again this is
a function of encoder strategy.  The Xiphophorus encoder will be
keeping streaming and multicast in mind.

Monty

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