[maemo-developers] Using available DSP tasks

[From: Jean-Christian de Rivaz]

Simon Pickering a écrit :
> 
>> If the DSP in not the limitation, then the N800 could be used for a
>> funny project I have now in my head. I there any documentation on how to
>>   program a Linux application to use some existing DSP tasks available
>> on the N800? I am interesting about the MP3 decoder and a pair of low
>> bandwidth coder/decoder like G711, G729 or ILBC.
> 
> There is source available for the ARM-side part of the gstreamer sinks 
> (http://repository.maemo.org/pool/chinook/free/source/g/gst-plugins-dsp0.10/). 
> That should show you how to use the dsp tasks.
> 
> There's a fundamental problem though, the mp3 dsp task sends its data 
> directly to the audio codec (hardware) on the DSP-side, therefore you're 
> probably not going to be able to access the raw data to reencode it as 
> something else (unless it is also exposed in a buffer in shared memory).
> 
> I am debugging an mp3 dsptask at the moment, so you may yet have 
> something to play with at some point in the near future if you can't get 
> the built-in tasks to work as you wish.
> 
> Cheers,

Hi Simon,

Thanks for your explanation.

After having read the basic Gstreamer documentation, I understand better 
the sink pad concept of the mp3 task. In the application I am thinking 
about now, I don't need to look at the raw audio data decoded by the MP3 
task as long as I can mix with it an other raw audio stream. I fact I 
need to mix a MP3 stream and a G711|G729|ILBC|AMR stream. You can see it 
as a kind of karaoke: mixing music (MP3) and voice (low bandwidth 
codec). The result should simply be available on the output jack.

Did you think it is already doable now ?

Best Regards,
-- 
Jean-Christian de Rivaz