[vorbis-dev] Reading OGG embedded in a pack file

[Ken Rogoway]

Thanks, I will give that a try.  I was thinking I would have to have the
'seek_tell' function return the size of the sub file (which is in my header
info).  Maybe that would be the right way to do it if I take your other
suggestion and doctor the seek requests by adding the starting offset.
Either way it sounds like I can get the desired results.

- Ken

----- Original Message ----- 
From: "Ralph Giles" <giles at xiph.org>
To: <vorbis-dev at xiph.org>
Sent: Saturday, April 17, 2004 12:03 PM
Subject: Re: [vorbis-dev] Reading OGG embedded in a pack file

<p>> On Sat, Apr 17, 2004 at 11:23:46AM -0500, Ken Rogoway wrote:
>
> > After looking at the documentation I thought I could change the 4th
parameter to be the offset into the stream for where my sub file (inside the
pack file) is located.  This did not work.  It took about 10 seconds for the
function to return so I am guessing it was seeking to the beginning of the
stream and then scanning forward looking for the OGG headers.
>
> No, the 3rd and 4th parameters are to let you provide a 'prefix buffer'
> in cases where the underlying file isn't seekable, but you've already
> read some of it to do filetype identification. Thus you can pass the bit
> you've read so vorbisfile can parse it, and then continue with the
> actual stream from the read position.
>
> Thus, your hypotheses is likely correct about what it's doing.
>
> > There are comments about using streams that are not "seekable" and I
thought this also might be a solution, but I could find nothing on how to
tell Vorbis that a stream was not seekable.  Is it as simple as setting the
callbacks.seek_func and callbacks.tell_func to NULL?
>
> You can set tell_func to NULL when the stream is not seekable. You must
> always provide a seek_func; the way you mark a stream as not seekable is
> by having that function always return (-1) for failure, regardless of
> the input. See http://xiph.org/ogg/vorbis/doc/vorbisfile/callbacks.html
>
> Another general solution of course is to doctor your read, seek, and
> tell callbacks to operate relative to the offset of the ogg data in
> your pak file.
>
> Hope that helps,
>  -r
> --- >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.
>
>

<p>--- >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.