[vorbis-dev] Xiph Magic

[Andrew MacLennan]

On Thu, 17 Jul 2003, Tor-Einar Jarnbjo wrote:

<snip>

> >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.

        I may be overlooking something very obvious (given that I haven't
had too much chance to study the Vorbis spec. yet), but I don't see how
Vorbis packets can be self-contained ie. in particular, how a decoder
might determine the end-of-packet condition without higher-level framing ?
Could you (or anyone) explain this a little more ?

Thanks,
Andy MacLennan.

--- >8 ----
List archives:  http://www.xiph.org/archives/
Ogg project homepage: http://www.xiph.org/ogg/
To unsubscribe from this list, send a message to 'vorbis-dev-request at xiph.org'
containing only the word 'unsubscribe' in the body.  No subject is needed.
Unsubscribe messages sent to the list will be ignored/filtered.