vorbis timeline

[Tim-Philipp Müller]

On Fri, 2013-05-24 at 09:40 +0200, lestoilfante wrote:

Hi,

> I tried oggz-dump on my files and the output is a bit different from
> that on radio.ogg you suggest where gpos start from xxxxx and continue
> to grow:
> (...)
> #oggz-dump video03.ogg |grep gpos|head pos
> 
> 00:00:00.000: serialno 1850673644, granulepos 0|0, packetno 0 *** bos
> 00:00:00.000: serialno 1850673644, calc. gpos 0|0, packetno 1
> 00:00:00.000: serialno 1850673644, granulepos 0|0, packetno 2
> 00:00:31.600: serialno 1850673644, granulepos 159|0, packetno 3 
> 00:00:31.800: serialno 1850673644, granulepos 159|1, packetno 4
>
> 
> So I have only one gpos for each file and a lot of granulepos with
> timing start at 0 and jumping to 15 sec on second file and so on. I'm
> not so much confident with ogg but why first packets on video02 and
> video03 start from 00:00:00.000 and jump to 00:00:15.000 and
> 00:00:31.600?

This is to be expected, I think. The first few packets are header
packets, which are supposed to have a granulepos of 0 according to
http://xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-130000A.2 (at least for
vorbis).

Cheers
 -Tim