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List:       kde-multimedia
Subject:    Re: Seeking in arts
From:       Stefan Westerfeld <stefan () space ! twc ! de>
Date:       2002-06-02 14:44:56
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   Hi!

On Sun, Jun 02, 2002 at 10:10:49AM +0200, Martin Vogt wrote:
> On Sat, Jun 01, 2002 at 09:00:03PM +0200, Ralf Schmelter wrote:
> >         player->play();
> >         player->seek(Arts::poTime(10, 0, 0, ""));
> This is too fast. The play call succeeds before the lenght
> is known. A seek is only possible, after you have the length.
> Reason: decoding runs in a seperate thread.
> (We really need a unthreaded mp3 decoder,any volunteers?)

There is an unthreaded mp3 decoder in gsl (its based on libmad), along with
an unthreaded ogg decoder. Hans Meine is currently doing a C++ wrapped version
of this, the plan is to have a PlayObject based on this before KDE3.1. Of
course this requires libmad then if you want to use this decoder ; and
streaming is missing, too.

I think the optimal way would be, long-term:

1. besides DataHandles, put another plain C API into GSL, that can decode
   streams
2. implement mp3/ogg/wav decoders there
3. wrap those into PlayObjects as required

The advantage of putting these in GSL is that they also can use the GSL partial
cache when used in music production, and sampleprecise synchronization. I.e.
it is possible to implement playing a well-defined piece of an mp3 file at a
well-defined position in a sequencer arrangement efficiently using the gsl
DataHandle code (you can't do that with the mpeglib PlayObject). It will even
be cached if you play it twice.

Its also possible to use this for offline decoding (such as in k3b), whereas
with the current PlayObjects, this is a bit contraintuitive.

   Cu... Stefan
-- 
  -* Stefan Westerfeld, stefan@space.twc.de (PGP!), Hamburg/Germany
     KDE Developer, project infos at http://space.twc.de/~stefan/kde *-         
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