alsa and sox questions

[Gregory Nowak]

Thanks Chuck. I'll try this out.
Greg


On Fri, Mar 29, 2002 at 04:55:15PM -0500, Charles Hallenbeck wrote:
> Greg -
> Your example showed that you did not use any parameters with the
> arecord command at all. No wonder it did not work!
> 
> I will include below a script which I use to record wav files but
> first I will talk about it.
> 
> The script contains some statements that let you use "ctrl-c" to
> interrupt a running program without interrupting the script
> itself. The reason is that I want to run arecord for an
> indefinite amount of time and interrupt it when the work is done,
> but I want the script to continue.
> When the recording is complete, I want to use sox to copy it to
> my home directory from the /tmp directory where it was created,
> so that sox can fix the length parameter in the RIFF header as a
> by-product.
> The script is called "rec22km" which means 22k sampling rate and
> mono format. I have other scripts for 22k stereo and other
> speeds, Mono and stereo. All the scripts produce 16 bit signed
> samples.
> The script can be run just by typing the script name, in which
> case the resulting file in your home directory will be
> "rec22km.wav", or you can include a name such as "myvoice" on the
> command line: "rec22km myvoice" and the resulting file in your
> home directory will be called "myvoice.wav".
> Once the copying is complete, the file is played just for kicks,
> and to verify that it worked. You can also interrupt the play
> command with ctrl-c and the script survives so that it can remove
> the /tmp file before exiting.
> 
> The parameters on the arecord command are what you have failed to
> include. I use "-d 7200" to allow a ridiculously long duration.
> This parameter was optional in earlier versions, but somewhere
> along the way the default duration became "0 seconds" so you have
> to give it a positive value.
> I use "-q" to throw away the reporting messages.
> I use "-r 22050" to set the sampling rate.
> I use "-f S16_LE" to specify the format of the output file:
> S16_LE means "signed 16 bit little endian". This parameter has
> changed regularly with each upgrade and is a pain in the ass to
> keep track of when you upgrade.
> I use the "-c1" parameter to specify one channel (i.e., monaural)
> and a space between the 'c' and the '1' is permitted but not
> required.
> Finally comes the file name.
> The trailing ')' on the arecord line of the script below belongs
> to the subshell interruption control from the previous line.
> 
> Sorry this has been so complicated, but once you get it going it
> works like a charm. Of course you must be sure you have enable
> 'capture' on the input source you want to record (you cannot just
> set your speaker level, since that is not the signal that gets
> recorded). For example you would want to mute your mike channel
> or turn the speaker volume off, but enable capture on the mike
> channel and adjust the capture volume appropriately. I have to
> use different capture volume settings for mike, CD, and Line, but
> once they are set, arecord works like a charm for me.
> 
> Here is the script:
> -------------
> #!/bin/bash
> trap "" SIGINT # ignore ^C
> (trap - SIGINT # except in this subshell
> arecord -d 7200 -q -r 22050 -f S16_LE -c1 /tmp/rec22km.wav )
> echo wait...
> if [ "$1" = "" ]; then
> sox /tmp/rec22km.wav rec22km.wav >/dev/null 2>&1
> echo rec22km.wav
> (trap - SIGINT # except in this subshell
> play rec22km.wav )
> else
> sox /tmp/rec22km.wav $1.wav >/dev/null 2>&1
> echo $1.wav
> (trap - SIGINT # except in this subshell
> play $1.wav )
> fi
> rm /tmp/rec22km.wav > /dev/null 2>&1
> -------------
> 
> HTH - Chuck
> 
> 
> 
> Visit me at http://www.valstar.net/~hallenbeck
> The Moon is Waning Gibbous (98% of Full)
> 
> 
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