[alsa-devel] How to tell user level hardware not support a certain format in a certain sample rate

[Takashi Iwai]

At Mon, 2 Mar 2009 22:04:04 +0800,
Richard Zhao wrote:
> 
> 2009/2/23 Richard Zhao <linuxzsc at gmail.com>:
> > Hi,
> >
> > runtime->hw.rates and runtime->hw.formats indicate the rate and
> > formats hardware can support, so the user level plugins can
> > auto-convert the audio data. But hardware may not support a certain
> > combin of sample rate and format, and will cause hw_parm fail. In such
> > case, plugin auto-convert will not work.
> > How can I let userlevel know the failure conbin, so let auto-convert work?
> >
> > Thanks
> > Richard
> >
> 
> Anybody can do me a favor please?

Could you be more specific, e.g. test cases with numbers?

There are some known problems with the configuration space reduction,
and I think your problem is one of them, though.  Basically, the
config space is reduced one after one for each
snd_pcm_hw_params_refine(), and the existence of a singular point
makes hard to pick up the right point.

If the problem is such one, currently there is no elegant solution.


Takashi