ramblin rec

[Geoff Shang]

On Sun, 24 Jan 2010, Brian Tew wrote:

> Right now my pc is a glorified amplifier. I can hear the mic
> thru my earphones, and cannot get it to stop.
> I turn down the volume with aumix to avoid feedback.

Your mic is probably not muted.  Try something like:

amixer sset Mic off

Note the two letter s's in sset.

This *should* mute your mic.  If it doesn't like the 'Mic" bit, run amixer 
without any arguments (probalby pipe it through more/less) and see what 
your mic channel is called.

Note that amixer is inthe alsa-utils package.  I'm recommending amixer 
because (a) I'm not very familiar with aumix, and (B) your message 
indicates that you're using ALSA.

Note that this assumes you hear your voice back immediately with no 
delay/echo.  If there is some kind of delay then this will be a different 
problem (see below).

> I can play wavs and mp3s just fine, but cannot record.
>
> I type:  rec -d foo.wav
> -d means use the default input device, which should be the mic.

I'm assuming this is rec as one of the forms of sox.  I couldn't find any 
documentation for a -d switch.  The default device, which referrs to the 
soundcard, not the channel on the card, will be used in any case, 
regardless of any -d switch (according to the sox manpage and my testing).

> linux replies: snd_pcm_open error: device or resource is busy

This indicates that something else has the card open.  Do you perhaps have 
something else managing yoru sound as part of Gnome or something?

You can probably find out what has the card open by using fuser, though 
exactly which device to search for I'm not sure.

> Something is forcing a connection from mic to pcm to earphones.

If you hear the mic back with no delay of any sort, then this is probably 
not the case.  the snd_pcm_open above refers to a function call called 
snd_pcm_open, which is not related to the PCM output channel of your 
soundcard.

Geoff.