[alsa-devel] need input on USB Audio class device.

Sakthi Subramanian sakthi.subramaniang at gmail.com
Mon Jan 31 11:21:34 CET 2011

Hi All,
i am trying to develop a ALSA record application for USB - Audio device.
This USB Audio device has stereo recording and 4 inputs (4 mics).
I am trying to capture PCM audio from the 4 mics using the simple record

Need inputs on the below questions, thanks in advance for the inputs.

1. I have used the ALSA API to set the number of channels as 8.
snd_pcm_hw_params_set_channels (capture_handle, hw_params, 8);

I have started capturing the data with the above change,
and opened the same using Audacity, it says 16 bit PCM Mono channel Little
in my opinion, that must show as 8 channel.

Am i calling the right API with parameters? or Please let me know how to get
the multi channel PCM capture data from ALSA?

This is the output of arecord -l:

# arecord -l
**** List of CAPTURE Hardware Devices ****
card 0: Device [USB PnP Audio Device], device 0: USB Audio [USB Audio]
  Subdevices: 0/1
  Subdevice #0: subdevice #0

Once again thanks a lot for ur inputs..

Sakthi  SG

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