[theora-dev] Timestamps...

Michael Smith msmith at xiph.org
Fri May 14 01:05:58 PDT 2004

On Friday 14 May 2004 17:59, illiminable wrote:
> Since we've been debating the merits of start or end timestamping... i'm
> curious why the page doesn't have both stamps ?
> That would solve the problems for all parties wouldn't it ?
> It's not like the overhead is huge... less than 0.1%... so on the average
> audio file thats 5 megs.... it's a 5k increase, which pretty much
> insignificant. Even on a 1gig video file it's only another 5 megs.
> Both stamps are usefull for their own things, and it would let all
> implementations be more efficient.
> Also the other thing i've been thinking about is the size of the timestamp
> field being only 32 bits... this means a limit of ~27 hours of audio at
> 44100. And there are certainly other applications (say a file with the
> years stock prices, earthquake data for the year etc)... there are times
> when you'd want to manitain a continuous single logical stream for long
> durations. In order to do this currently you'd have to somehow denote
> someway to indicate where the granule pos resets, which would also totally
> mess with all the seeking algorithms.

granulepos is 64 bits, not 32. 

This presumably means your overhead calculations are off too. Regardless: the 
reason not to require both is that it's not useful - given one, the other can 
always be calculated (from the packets in the page - in a codec-specific way, 
of course). The calculations aren't complex or heavy-weight either, so the 
'efficiency' argument doesn't seem (to me) to hold much water - you still 
need to convert your timestamps to the 'native' representation of your 
framework, so you also can't argue that this means you can avoid 
codec-specific calculations at this stage.


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