[vorbis] Tool for cutting Ogg Vorbis files

[Oscar Sundbom]

On Fri, 26 Mar 2004 22:17:04 +0800
Cameron Patrick <cameron at patrick.wattle.id.au> wrote:

> Karl Ove Hufthammer wrote:
> 
> | BTW, the mp3DirectCut author says this in his FAQ:
> | 
> |         Can you add Ogg Vorbis support?
> | 
> |         I would, but Vorbis seems to be much more difficult to
> |         cut than MP3. An MP3 can be cut everywhere and it's
> |         still playable. Cutting an Ogg file without adapting
> |         anything here and there will produce broken files. I
> |         could not find any understandable documentation of a
> |         structure in Vorbis files. If you know such docs, please
> |         let me know.

Cutting an MP3 at an arbitrary point in a file, except on a frame boundary, will
produce a broken frame, but most players will still play it after seeking to the
next (complete) frame. If mp3DirectCut implements cutting of MP3 files this way,
someone should inform him his software produces erroneous files.

> That's incorrect, Vorbis files can be cut on arbitrary sample
> boundaries, which AFAIK is with greater precision than MP3.  At one
> point there was a tool "vcut" floating around which would do this.
> I'm not sure if it's still around or what its status is though.

Vorbis does, from what I gathered, include a header (per logical bistream) with
data that's needed for decoding (codebooks, I think). It can be cut on arbitrary sample boundaries
in the sense that some extra data will be saved in the frame, but it will not be played due
to a value in the header.
 
When I last checked, vcut was part of vorbis-tools (utils?) and was considered experimental.

> Cameron.

Anyone, please, correct me if I'm wrong. :)
Oscar
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