theora dev - Jun 2008 - current_granulepos-first_granulepos ?

Hi,

Is it correct to assume that after I get the headers of a stream like theora or
vorbis the packet time can be computed as
current_granulepos-first_granulepos ?

This would give me the difference between the first media packet that is not a 
header and the current packet I decoded most recently. In a live stream I would
have a
clock from this calculation starting at zero.


Thanks 


      
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
http://lists.xiph.org/pipermail/theora-dev/attachments/20080622/08dd48a4/attachment.htm

2008/6/23 Jim Smith <jimjim197 at yahoo.com>:
> Hi,
>
> Is it correct to assume that after I get the headers of a stream like
theora
> or vorbis the packet time can be computed as
>
> current_granulepos-first_granulepos ?
>
> This would give me the difference between the first media packet that is
not
> a
> header and the current packet I decoded most recently. In a live stream I
> would have a
> clock from this calculation starting at zero.
not quite, because the first_granulepos denotes the time of the end of
the last packet in the first page -- if there are many packets in the
first page (as is common for vorbis), then there will be a difference
between the time of the start of the stream and first_granulepos.

Shane Stephens wrote some (nasty) code for calculating this for vorbis
etc. (in http://trac.annodex.net/browser/liboggz/trunk/src/liboggz/oggz_auto.c).
Of course I'd suggest you just use liboggz rather than re-implementing
that.

cheers,

Conrad.