[vorbis-dev] q re vorbis packetizing in ogg stream

Mike Coleman mkc at mathdogs.com
Wed Apr 25 13:58:02 PDT 2001

Michael Smith <msmith at labyrinth.net.au> writes:
> Correct. The first packet must be on a page by itself (this is true for all
> ogg streams, and is enforced by libogg).
> The requirement that the audio data begin on a new page was added later, it
> wasn't there originally.  It's needed because otherwise streaming is overly
> complex. Playback works regardless.

Okay, so this *is* now a requirement, correct?

> >It seems like it would be easier for tools which manipulate the comment or
> >codebook headers if each of these headers was required to be placed on its
> >own page.  Any thoughts on this?

> As someone who has written many (most?) of the available tools to
> manipulate vorbis files in such ways, I feel qualified to answer this. It'd
> make it _very_ slightly easier, but not significantly so - so it's not
> worth changing the spec for this. It only makes the simple case slightly
> simpler - and since one has to implement the complex case anyway (where the
> packet doesn't fit onto one page - common for the codebooks, less common
> but very possible for the comments), it's not a great help.

I was thinking that it would be easier in that if, say, you wanted to replace
the comments in an ogg vorbis file, you could just cut at the dotted lines
(i.e., the ogg page boundaries at the beginning and end of the comment header
packet), generate your own new comment header packet, and reassemble.  (I
guess since the packets are numbered, you potentially have to renumber the
entire stream, though.  Ugh.)

Note that I'm considering general manipulation of these files, not necessarily
using libogg, etc.

Anyway, I defer to your experience with this.

Mike Coleman, mkc at mathdogs.com
  http://www.mathdogs.com -- problem solving, expert software development

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