[LAD] supporting a dedicated DSP chip with ALSA

Ziv Haziz Ziv.Haziz at dspg.com
Sat May 30 17:49:10 UTC 2009


> i'm seeking an advise on the preferred way to support a dedicated DSP
> chip under ALSA.

> Unfortunately ALSA is pretty bad on abstracting anything else except
PCM
> streaming and MIDI.

As far as I have looked inside the ALSA API there is support for
"special" format and GSM format so ALSA can pass encoded data.

Also since this is an embedded system I can control exactly the DSP
peripherals connected to the system so I may "trick" the system.

> For ages I have been concerned about how to support hardware
accelerated
> (DSP) 3D audio. OpenSL ES seems to be the only option at the moment.

> The DSP core is capable of both playing both encoded streams (mp3,
wma,
> various voice coders) and of course PCM streams.
> the codec (a2d, d2a) are  connected to DSP.

> I think you might have better luck by using OpenMAX[1], it has been
> designed for this kind of use.


The problem with OpenMAX is that most of the common players (at least
the ones I looked into mplayer and mpg123) doesn't support them
natively.

 

If I will use sample format "special" will the alsa know not to try and
do manipulation over it? (resampling, volume, etc...)

 

And last question - in the LADSP interface file I have seen that I can
be a control plug-in - this means that ALSA will pass all control signal
to me including rate, volume, open close and other?

Thanks,
Ziv
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