[vorbis-dev] Xiph Magic

[Tor-Einar Jarnbjo]

>Then FLAC has duplicate framing information when encapsulated in Ogg.
>You can determine where a packet ends from the packet itself.  

Yes, the decoder knows when a packet is finished and the next packet 
will begin on the next boundary. Except from that, there are no additional 
framing informatioon in a raw FLAC file.

>I'm not
>sure about Speex but I'm pretty sure that Vorbis packets are not
>self-sized.  If not, how come simply trimming (non-header) Vorbis
>packets is supposed to produce a legal Vorbis file?  Quoting the spec:
>"Vorbis provides none of its own framing, synchronization or
>protection against errors".

In theory, it is possible to decode an incomplete Vorbis packet and 
still render some sort of audio output. In a Vorbis packet, the order 
of information is sorted according to importance, so if the last 
part of a Vorbis packet is missing, the decoder could be (according 
to the spec probably should be) able to produce audio output with 
minial distortion.

In the normal case (and I am quite sure, that the common players 
would fail playing a properly Ogg-framed Vorbis stream with incomplete 
packets), the packets are complete and the decoder is able to determine 
the end of a packet without relying on the Ogg framing.

Tor

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