[vorbis-dev] Xiph Magic

[Beni Cherniavsky]

Tor-Einar Jarnbjo wrote on 2003-07-17:

> >I just wonder what is "Native Vorbis" and "Native Speex"?
> >It seems that you are detecting standalone Vorbis/Speex packets with
> >no wrapper whatsoever.  The problem is that such a thing is
> >undecodable - you need some way to mark the packet boundaries.  So no
> >such beasts exist.  Flac does exist outside of Ogg but it uses its own
> >framing then.
>
> That is not correct. A "raw/native" FLAC file has no additional framing
> information. Simply removing the Ogg page headers from an Ogg/FLAC
> file would certainly produce a decodeable FLAC file. I'm not sure
> about Speex, but at least for Vorbis, it would certainly be possible
> to decode such a file. Seeking would be a little bit difficult, but
> still very much possible.
>
Then FLAC has duplicate framing information when encapsulated in Ogg.
You can determine where a packet ends from the packet itself.  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".


-- 
Beni Cherniavsky <cben at tx.technion.ac.il>

If I don't hack on it, who will?  And if I don't GPL it, what am I?
And if it itches, why not now?  [With apologies to Hilel ;]
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