[LAD] Hardware audio decoder driver design

Nikita V. Youshchenko yoush at cs.msu.su
Thu Jul 28 14:51:55 UTC 2011


> Nikita V. Youshchenko wrote:
> > Soon I will work on a linux kernel driver for a custom audio decoder
> > device that is being developed by a company I work for.
>
> Kernel sound programming would be discussed on the alsa-devel list.

Thanks for your reply. Will ask there now.

>
> > If not going into details, that devices reads A52-encoded stream
> > from system memory, and writes raw pcm stream to system memory.
> >
> > Simplest thing to do is - implement a character device, where
> > user-space will write encoded stream, and from where user-space will
> > read decoded stream.
> >
> > However, perhaps a better architecture (e.g. in-kernel intergation
> > with an audio sink) is possible?
>
> One of the implicit assumptions of ALSA sound devices is that they run
> in real time, and at a constant bit rate.  As far as I can tell, your
> device would be 'just' a DSP, so a character device would be
> appropriate.

But there is such thing as 'ac3 passthrough' - to make use of hardware ac3 
decoders on sound cards that have this feature.
I was thinking that something similar could be done for 'our device + 
standard alsa driver' combination - to make use of existing software using 
that interface.

Nikita



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