Re: [Alsa-user] help with using rear connector as a separate channel

[Niv <niv...@fa...>]

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here is my response , with fixed error msg:
Adam Nielsen wrote:
| You realise this would mean one audio device would play out of the front
| speakers and a different one out of the rear speakers?  i.e. if you're
| listening to music and you want to put the headset on, you'll need to
| stop the music, change the audio device, then start the music again...
yes, this way I may hear skype ring in the front speakers , and conduct
the call using the headphones to avoid audio feedback.

|> I tried this in my .asoundrc file:
|>
|> pcm_slave.via4 {
|> ~    pcm "hw:0"
|> ~    channels 4
|> }

| This is a complete guess, but does it work if you use "surround40" as
| the slave device?  (either in the pcm.ch34 or via4.)  I'm guessing the
I tried replacing the "hw:0" with "surround40" - got an error.
then changed it back to "hw:0" and changed the line slave to
"surround40" - got an error. finally I replaced the two places with
"surround40" and got an error.

| problem lies in that you've got two 2-channel devices, and you're trying
| to mix them into a single 4-channel device - i.e. ALSA expects four
| incoming channels from each stream, but you're only delivering two.
| Presumably you'll need something like this:
|
| pcm.ch34 {
|   ...
|   bindings {
|     null 0    # Not real code, just illustrating a point
|     null 1
|     0 2
|     1 3
|   }
| }

I tired this in my .asoundrc:
pcm.ch34 {
~        type dshare
~        slave via
~        ipc_key 47110816
~        ipc_key_add_uid no
~        channels 2
~        bindings {
~                  0 2
~                  1 3
~           }
}
I got this error:
$ aplay -D ch34 sound.wav
ALSA lib pcm_direct.c:1464:(_snd_pcm_direct_get_slave_ipc_offset)
Invalid type 'dshare' for slave PCM

I then tried the lines you suggested, got the same error. in any case I
would still want to use the front channels to output music , while using
the rear to conduct a phone call simultaneously.

| Cheers,
| Adam.
thanks,
Niv
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