"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
=================
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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