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List:       kde-multimedia
Subject:    Re: audio file decoding with aRts (for cd-writing)
From:       Stefan Westerfeld <stefan () space ! twc ! de>
Date:       2002-04-01 17:49:46
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   Hi!

On Sun, Mar 31, 2002 at 12:42:16PM +0200, Sebastian Trueg wrote:
> it's been a while since I posted an equal question and I hope that in the 
> meantime some things have changed or become easier...
> I'd like to add decoding via aRts to my cd-writing app K3b. Is the PlayObject 
> still the only thing one can use to decode audio-files?
> I need to decode an audio file into a raw audio stream to either write it to a 
> file or stream it to cdrecord/cdrdao. Is this possible?

Well, PlayObjects are still the only solution that are part of the public
and stable API. So if you want to do something that works under KDE3.0 and
upwards, you'll have to use this.

However, what changed is that there is code in the CVS already that can decode
wav and ogg files (without using a PlayObject) directly, and Tim is also
working on code for mp3 files. This code can be found in
arts/flow/gsl/gsldatahandle*. It offers something like:

 * give me a data handle for this file
 * how many samples are in this data handle?
 * give me N decoded samples (as floats) at a certain offset

Currently, the datahandles have the following properties:

 * they are quite lightweight
 * they get the timing right
 * they don't resample, so they doesn't change the data you decode
 * they are not too well tested
 * they are not part of the public API
 * they are partially cacheable (wavecache)

However, this is at most a future solution, that is: it would be great if
these data handles could be wrapped suitably and added to the public API for
something like the next aRts version or something like this. Then, they would
probably ideally solve your problem.

   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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