[vorbis-dev] Vorbis packet sizes

[Beni Cherniavsky]

John Ripley wrote on 2003-06-05:

> Beni Cherniavsky wrote:
> >
> > There is no bound whatsoever on packets.  There is a limit on the
> > size of a page - just below 64KB.  Packets can span multiple
> > pages, which is the only limitation to reading entire packets.
> > I/O should be much slower than moving around memory anyway.
>
> That's the point, I/O is slow and may block, which then involves a
> context switch. If you want the ability to context switch, you
> suddenly need a separate stack (or thread if you're running a big
> OS). If you take all the I/O out of the decode path, it won't ever
> need to context switch.
>
How do you take all I/O out of the decode path?  I'm afraid I missed
you intent, please explain again.

> > Multiplying max page size by page sequence number limit, you can get a
> > theoretical limit of packet size but that would be ridiculously big.
> > Ogg intentionally supports arbitrarily big packets.
>
> The "unknown" and "arbitrary" upper bounds of Vorbis streams is something I
> don't particularly like. However, if you assumed stereo (I'm throwing away
> anything with more), 8192 block size, and worst case entropy (all codes are
> 32 bits), I bet it would still be reasonably small. I'll calculate this when
> I have some spare time.
>
It might make some sense to place bounds on packets size in specific
use areas.  It most certainly doesn't belong in the Ogg framing
standard, I think it's wonderful that it does not place constraints.


-- 
Beni Cherniavsky <cben at users.sf.net>
--- >8 ----
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