Version 0 of A Radio Recorder

A Snack based application.

I enjoy talk radio, but some of my favorite shows play when I don't have access to a radio (like when I'm sleeping, for example). I finally got around to enabling the sound card on my UNIX server (Slackware 8 based). I installed the Linux Alsa drivers, which appear to work just fine.

Anyway, I figured I could just connect the Line-out from an available radio into the Line-in of the UNIX server machine, and record the programs. Well, being a Tcl kind of guy, I immediately thought of using Snack. I wanted the output to be in mp3 format, so I also have to use another application (Snack doesn't support mp3 for output). The following is a summary of the process, which might be useful to a few others.

Here are the components that make up my Radio Recorder:

cronjob - schedules the recordings. UNIX only, but other platforms have equivalents.
Tcl - Needed for Snack. Available for all platforms.
Snack - Extension to Tcl. Controls the audio card mixer and reads the Line-in and writes to WAV format. Available for all platforms.
lame - An mp3 encoder that converts the WAV output from Snack to mp3 format. Available for all platforms.

Here's the small Tcl program that's the core of the process. Since it's not a Wish application, it does a 'package require sound' instead of 'package require snack'. The snack package includes widgets, so you can't load it into a tclsh application. It sets the gain for the Line-in, reads the Line-in at 16000 sampling (remember, I'm recording talk radio, so this is plenty) and writes to stdout in WAV format. It takes one parameter, the number of seconds to record.

  #!/bin/sh
  # \
  exec tclsh "$0" "$@"

  package require sound

  set ::left  90
  set ::right 90

  snack::mixer volume IGain left right

  snack::sound ss -channel stdout -rate 16000 -channels Mono
  ss record -input Line1 -fileformat WAV

  after [expr [lindex $argv 0] * 1000] exit

  vwait forever

The output from this program is piped through lame to write the final output to an mp3 file. One hour of recording generates a ~10 MB file.

Here is an example shell script that gets run from a crontab entry. It creates a 1 hour time-stamped recording, storing it on a network accessible drive

  #!/bin/sh

  DEST=/mnt/bilbo/windows/MP3/Radio/DougMcIntyre

  TOD=`date +%d%b%Y_%H%M%S`
  exec /usr/local/bin/tclsh $HOME/radio/radiorecorder.tcl 3600 | /usr/local/bin/lame - $DEST/DougMcIntyre$TOD.mp3

That's it. I have various cronjobs that make hours of recordings of my favorite programs. I use Snackamp [L1 ] to play back the radio shows on any of my Windows or UNIX machines. My next step will be to get an AM/FM tuner card that I can install in the server (anyone know of a good one?).

Marty Backe 07 Aug 2002