Vorbis dev - May 2004 - Calculating vorbis packet durations...

After a few other attempts at hacks to determine start times of pages, the
only other option left is to partially decode the packets in the demuxer in
order to give correct start time stamps after a seek.

Someone mentioned it was relatively easy to do without a full decode. I've
had a bit of a search in the mailing lists and on the web and can't find any
details about it.

What i need is to be able to calculate the duration of all complete packets
on a page such that i can subtract it from the end granule pos.

Can someone point me to some psuedo-code or actual code of how to do this ?
I assume the info needed is stored somewhere in the vorbis packet. I'm also
looking for the same information for speex also.

Thanks

Zen.

<p><p>--- >8 ----
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I had this problem and after a "few"searches I came to this method:

first decode and setup the ogg file until the point u find the modes
configuration.

If u have the previous page, save the granule postition.
while( !endOfPackets)
    {
    getPacket;
    check if this is and audio packet;
    read window configurations;
    thisPacketSize = previousPacketWindowSize/4+ thisPacketWindowSize/4;
    packetsGranule += thisPacketSize;
    realGranule = lastPageGranule+packetsGranule;
    }

if u want u can save packets granule inside a realgranule vector. I haven't
covered the case where the page is a continued page

<p>Hope it helps

<p>----- Original Message ----- 
From: "illiminable" <ogg@illiminable.com>
To: <vorbis-dev@xiph.org>
Sent: Tuesday, May 18, 2004 6:59 AM
Subject: [vorbis-dev] Calculating vorbis packet durations...

<p>> After a few other attempts at hacks to determine start times of
pages, the
> only other option left is to partially decode the packets in the demuxer
in
> order to give correct start time stamps after a seek.
>
> Someone mentioned it was relatively easy to do without a full decode.
I've
> had a bit of a search in the mailing lists and on the web and can't
find
any
> details about it.
>
> What i need is to be able to calculate the duration of all complete
packets
> on a page such that i can subtract it from the end granule pos.
>
> Can someone point me to some psuedo-code or actual code of how to do this
?
> I assume the info needed is stored somewhere in the vorbis packet. I'm
also
> looking for the same information for speex also.
>
> Thanks
>
> Zen.
>
>
>
> --- >8 ----
> List archives:  http://www.xiph.org/archives/
> Ogg project homepage: http://www.xiph.org/ogg/
> To unsubscribe from this list, send a message to
'vorbis-dev-request@xiph.org'
> containing only the word 'unsubscribe' in the body.  No subject is
needed.
> Unsubscribe messages sent to the list will be ignored/filtered.
--- >8 ----
List archives:  http://www.xiph.org/archives/
Ogg project homepage: http://www.xiph.org/ogg/
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