[linux-audio-user] aplay, plughw, alsamixer question

[Clemens Ladisch]

Mark Knecht wrote:
>    This info is to help me do more debug work on a new HDSP 9652 driver
> version that I am helping to test.
>
>    Should the volume levels I hear when using the command
>
> aplay -Dplughw:0 -r 44100 data/wave/seque~10.wav
>
> be controlled by alsamixer?

Depends on the hardware (or the driver). Many cards have a mixer for
certain output streams and/or a master mixer, some don't. (ALSA
doesn't modify volume levels in software by default).

>    Also, on a multichannel card, how do I direct the above aplay command to
> a specific channel? I am finding that with this new driver the audio is
> appearing on ALL channels on the card, even for a mono wave file. I think
> this is a bug, but I'm not sure.

The plughw plugin automatically converts sample formats. To access the
hardware directly, use "hw:0" instead of "plughw:0", but this won't
work if your file isn't exactly in a format supported by the hardware.

To access a subset of the channels, you can use the route plugin IIRC.
The "documentation" at
<http://www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html> lacks
the interesting parts, so try to search in the list archives.


HTH
Clemens