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

[Mark Knecht]

Clemens,
   Thanks very much for responding. A couple of questions below.
Cheers,
Mark

On Sat, 2003-07-26 at 04:37, Clemens Ladisch wrote:

> 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).

OK, so the RME HDSP 9652 has a mixer as I use it under Windows. In this
case, I would assume that alsamixer would not show mixer controls if the
driver didn't tell it the hardware had a mixer? 

To clarify, what I'm understanding is that since Alsa doesn't modify
volumes in software, then the hardware has to do it, and the alsamixer
controls (or amixer controls) show the levels that Alsa is telling the
hardware to modify volumes by?

Makes sense, I think...


> 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.

Very helpful. plughw would address having the card in a certain
frequency mode, but playing a file recorded at a different frequency.
This is great from a user's POV. Thanks.

I suppose hw:0 would be sensible if I recorded from the card, saved in
the card's data format, and then wanted to play that back. Sounds
efficient.

> 
> 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.

Will do. Maybe this route plugin will help me test which channels are
and are not working with this new driver.

Thanks!

Cheers,
Mark