Cyclic sound MP3 audio recording in ubuntu




I work in a relatively safe environment, yet it may very well happen that I need to prove something that someone said in my office, so I can hold it against them when the time comes.

My laptop is always turned on, so I could use it to record the environmental sounds around it, with a couple of requirements:

  • the recording must be totally unattended, starting when I turn on the pc, and stopping when I turn it off, without any user intervention
  • the recorded files must be somehow purged, starting from the oldest ones, so that my disk doesn’t get filled with audio files

As in the Ubuntu spirit, I tried to search for something that did the job right away, but with no luck.

So, still in the Ubunt spirit, I had to arrange it myself: the idea is to record the audio in chunks of 10 minutes, and each time delete the oldest files, so that there is a chosen number of max files inside the recording folder.

You will need the audio-recorder package for the job, install it as follows:

sudo apt-add-repository ppa:osmoma/audio-recorder
sudo apt-get update
sudo apt-get install audio-recorder

when the program is installed, open it (Alt-F2 and then launch audio-recorder), click on the “additional settings” button, and setup your default recording folder there, in this example it’s the folder “audiofiles” directly under your home folder.
Also I suggest changing the file naming standard to %Y-%m-%d-%H:%M:%S so that each recording can be easily associated with the time of starting.

Then, you need to make a bash script that will deal with starting a new recording, while closing the previous one, this is what I came up with:

#!/bin/bash

/usr/bin/audio-recorder --display=:0.0 -c stop
/usr/bin/audio-recorder --display=:0.0 -c start
cd /home/username/audiofiles
rm `ls -t | awk 'NR>150'`

which does exactly the following: stops a previously open (if existing) instance of the program, and starts a new one, then deletes the oldest recorded audio chunks so that there are maximum 150 files inside the recording folder (if you want a different amount, just replace 150 with the number you prefer); please note that the recording folder written in this bash script must be the same that is set in the additional settings, so if you want to use a different folder make sure to set it up both in audio-recorder and in this bash script.
Also, please note that the username part of the path must be replaced with your ubuntu username.

You can create this bash script as a “recordaudio.sh” file in your home folder, and then be sure to chmod +x recordaudio.sh so you can execute it.

Then, you need something that actually starts the recording, and cron is our friend here.

Run the command

crontab -e

and if it’s the first time you run it,  you should be presented with a choice screen asking you which editor you prefer… absolutely choose nano!

Inside the editor screen, paste this:

*/10 * * * * /home/username/recordaudio.sh

where “username” must be replaced with you ubuntu username, then press Ctrl-X to save the file (press Y is prompted to confirm).

What this cron line does, is running the bash script we just created every ten minutes, so the recorded sound files will be 10 minutes long. If you want to change this length, just change the 10 in the command to the number of minutes you prefer.

Restart the pc, and notice how files are being created inside of your folder. After a while, you will also get over the set limit for the files, and you will notice how the number of files will always stay the same, with the oldest files being deleted.




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