>
>
>
> "Dual mono" is indeed an AAC-related concept.
>
> When you record multiple channels using ALSA, they are always independent,
> i.e., ALSA does not make any assumptions about the sample values in the
> channels (or, for that matter, about consecutive samples in the same
> channel).  In other words, you need not (and cannot) tell ALSA whether the
> channels are related in any way.
>
>
>
Hi,

Thank you for the information.
I understand that mono/stereo is not related to ALSA (probably only to the
compression method, external to ALSA)

I hope you can help me understand better the idea of channels with alsa.
I am using card with playback device and capture device.
It seems to me that playback has 2 channels and capture has 2 channels each.
The physical connection is:]

   - mic input
   - line input
   - line output
   - headphones output

This is the proc info
=================

root@dm814x:/mnt/nfs# cat /proc/asound/card0/pcm1p/info
card: 0
device: 1
subdevice: 0
stream: PLAYBACK
id: AIC3X tlv320aic3x-hifi-1
name:
subname: subdevice #0
class: 0
subclass: 0
subdevices_count: 1
subdevices_avail: 1
root@dm814x:/mnt/nfs#

root@dm814x:/mnt/nfs# cat /proc/asound/card0/pcm1c/info
card: 0
device: 1
subdevice: 0
stream: CAPTURE
id: AIC3X tlv320aic3x-hifi-1
name:
subname: subdevice #0
class: 0
subclass: 0
subdevices_count: 1
subdevices_avail: 1

I have looked in the use APIs of alsa, but I can't figure out the channel
usage for controlling the route.
If for example I want to capture only one of the channels (mic in), how do
I do it using snd_xxx api  ? The same goes with playback, which API do I
have so that I control the data for specific channel ?


Thank you!
Ran
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