[theora-dev] Re: Ogg mux design

Monty xiphmont at xiph.org
Mon Feb 16 18:12:01 PST 2004

On Mon, Feb 16, 2004 at 06:05:13PM -0800, Ralph Giles wrote:
> On Mon, Feb 16, 2004 at 07:41:05PM -0500, Monty wrote:
> > Yes, I remember this.  Unfortunately it makes some repagination
> > operations impossible, as you can't as easily reconstruct granule
> > positions going backwards.  You have a granpos for every packet in
> > encode; you may not be able to regenerate that later.
> No it doesn't. To summarize an irc discussion; while there are 
> differences in the corner cases, neither of us sees a significant 
> difference between the ordering of the two schemes.
> What *is* different is the fact that you can flag a bitstream as being 
> 'continuous' or 'discontinuous'. The codecs must know this and be able 
> to tell the mux layer in the case of a given substream. Thus, Monty's 
> proposal sneaks in an element of the old metaheader proposal in that the 
> codecs can give hints to the mux layer about which streams to buffer and 
> which to drop.
> That's the substance of the difference. I still think it's not worth it, 
> and he does. Any other arguments? :)

There's a second larger difference; ordering everything by start means
granule positions are no longer in monotonically increasing order.  I
have to seek according to start time (to make the bisection work)
which means I must recalculate start granules for any seek operation.
The way things are right now, the granpositions as encoded are the
ones I use directly.

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