[alsa-devel] Hidden rate conversion, and Alsa configuration

[Lee Revell]

On 7/27/07, stan <stanl at cox.net> wrote:
> On Fri, 27 Jul 2007 11:59:53 -0400
> "Lee Revell" <rlrevell at joe-job.com> wrote:
>
> > On 7/27/07, Alan Horstmann <gineera at aspect135.co.uk> wrote:
> > > Could you give pointers as to how to modify Alsa configuration so
> > > that rate conversion can never happen, as I would prefer to have an
> > > error accessing the sound card rather than unknown conversion,
> > > which in my use should never be neccesary anyway.
> >
> > Simply open the hw device rather than the default, dmix, or plughw
> > device.
> >
> > Lee
>
> Lee,
>
> Are you saying that plughw *does* do hidden conversion?  I thought its
> definition was equivalent to
>
> newplug {
>         type plug
>         slave {
>                 pcm "hw:0,0"
>         }
> }
>

It's not "hidden" conversion, by using the plughw device you are
explicitly asking ALSA to convert the PCM stream to a format the
hardware supports.

Lee