Re: Recording specific channels

On 2024-05-10 23:56, Michael Cottle, (David) wrote:

> I need to record specific channels from a multi-channel interface.

I would GUESS that how you do this depends on whether the audio 
interface(s)
always send all channels of audio, or only those you choose on the 
inteface
itself.

Then the file (or stream) of audio might contain header info saying (to 
sox)
how many channels of data are being sent.  Or it might not in which case 
you
would HAVE TO TELL sox what is coming in.


According to the so manual, sox can be told via   -c n    eg -c 4   that 
the
incoming audio contains that number of channels ... so your example of 
-c 2
doesn't seem right to me unless the interface was ONLY SENDING 2 
channels of
audio.


If eg you have an 8 channel interface configured only to send 5 channels 
I've
no idea whether sox would know there's 5, or know there could have been 
8,
or be sent 8, 3 of which are silent, or have no idea at all.  Presumably 
the
manuals for the interfaces will tell you...  Alternatively you could use 
soxi
to find out what is in the file according to its headers.


If sox is being sent, say, 5 channels of audio, you use the "remix" 
effect
to map selected input channels onto the desired output channels.


-- 
Jeremy Nicoll - my opinions are my own