[alsa-devel] New Audio Driver Design

Daniel Mack daniel at caiaq.de
Mon Jul 20 08:56:39 CEST 2009

On Thu, Jul 16, 2009 at 09:13:28AM +0900, jassi brar wrote:
> On Thu, Jul 16, 2009 at 5:22 AM, Daniel Mack <daniel at caiaq.de> wrote:
> > Are these decoder instruction something you need to do at runtime? Or
> > would it suffice to provide them once when the driver is probed?
> The decoder insn, params atleast, depend upon the mp3 file i want the dsp to
> decode and play.
> So, let us assume, i have to load decoder insns and params into the dsp for
> every mp3 file playback.

Then the alsa control API seems appropriate. Unless there is any other
interface for that specific purpose I'm not aware of.

> Also, by what interface name(like I2S/PCM/AC97) shud my driver get encoded
> mp3 data from my mp3-player and then decode that mp3 data by dsp and play
> the output pcm stream?
> I am afraid i must bypass/hack ALSA stack to directly get mp3 data from
> user-space. Am i right?

Have a look at include/sound/pcm.h - there are more formats defined than
just linear PCM, and I think SNDRV_PCM_FMTBIT_MPEG could be something
you can use. But I'm not sure and never used something like that before,
so maybe anyone else can elaborate more?


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