[alsa-devel] Reg: Implementation of GSM digital audio path

[shariff]

Hi Peter,

         Thanks for your suggestions.

         I have one more question:

         In GSM mode. I have to also take audio data from TWL4030 MIC input
and redirect to GSM.

         From your theory,  If

                          0.0: TWL digital audio
                          0.1: My GSM codec

                          arecord -Dplughw:0.1 | aplay -Dplughw:0.0
GSM to TWL4030.

                          Can I specify,  for TWL4030 to GSM

                          arecord -Dplughw:0.0 | aplay
-Dplughw:0.1            .Is this the correct thing? Can  I both things at
the same time?


        If I want to record a GSM call?  I have to record both the
conversations and copy in one file. since here both the buffers are
independent.

        How this can be done?



Thanks & Regards,
Shariff

On Thu, Jun 25, 2009 at 5:02 PM, Peter Ujfalusi <peter.ujfalusi at nokia.com>wrote:

> On Thursday 25 June 2009 14:11:04 ext shariff wrote:
> > Hi Peter,
> >
> >       Thanks for quick response. I understood some what from your mail.
> >
> >       I will explain, how my hardware is connected.
> >
> >
> >                         USB GSM chip -> McBSP3
> >
> >                                                     McBSP2 -> TWL4030
> >
> >       Here, playback functionality will not be there in the GSM path. I
> > need to take audio data from GSM. and redirect this to TWL4030 codec.
>
> I see. Sorry I have confused things a bit,
> In this case you need to do what Mark has suggested:
> dummy dai for the codec, connect it to McBSP3 as it were a normal codec.
> Than you will have two PCM on the sound card:
> 0.0: TWL digital audio
> 0.1: Your codec
>
> arecord -Dplughw:0.1 | aplay -Dplughw:0.0
> or
> arecord -Dhw:0.1 | aplay -Dhw:0.0
>
>
> >
> >       The thing is, How and where to implement this GSM path without
> > playback? as I am new to this ASoC framework.
> >
> >       What I understood from ur mail is.  Audio is being redirected from
> > the application space i.e arecord will record and store in buffer and
> this
> > buffer is
> >
> >       being played using aplay to other hardware (twl4030).
> >
> >       Can we handle the same thing in kernel space ( i.e in driver
> itself).
>
> You anyway have to copy from one buffer to another to be in the safe side
> (in
> theory you could use the same buffer for recording and playback, but it
> should
> be avoided).
> So you have to copy the samples from the capture buffer to the playback
> buffer. It really does not matter if it is done inside of the kernel or in
> user space.
> This kind of 'routing' clearly belongs to the user space.
>
> >
> > Regards,
> > Shariff
>
>
>
> --
> Péter
>