Monday, July 7, 2008

Audacity Recording Tips and Crash Recovery

Info from the following URLS:

Continuing from my previous post on installing Audacity, a thought later came into my mind - "Why not just use the Eee PC to do the recording?" There would be no need to charge any rechargeable batteries, no fear of the batteries running out, no need to worry about exceeding disk space, plus recordings could be recovered should the device crash and most importantly, there would be a spectrogram to show whether anything is being recorded DURING the recording.

I just tried it for the first time last Sun, 06 Jul 2008, with 1 person from the church PA crew manning it. A line-in cable connected to the mixer was plugged into the EeePC's microphone port. Here are some tips that I have learnt:

  1. Remember to plug in AND switch on the power supply. At the end of the service, my friend told me that the Eee PC suddenly shutdown by itself. I checked and found out that I had plugged in the power supply but forgot to switch it on. More on crash recovery below.

  2. Adjust the microphone volume to ONE-QUARTER of its maximum volume. When I first tried it on the PA system, I turned on my Eee PC mic volume full, and the recording was full of distortion and background noise. I thought it was finished. Later, I played with the Sound Recorder provided under the Play tab and discovered the Input Level which pointed out the problem. NOTE: When you mute and unmute your volume, it seems that both the speaker and mic volume are reset to zero. Always do a check before you start your recording.

  3. Though you can export as an MP3 file, the recording is in uncompressed WAV format. For 60 mins of recording, you would need roughly 900MB of disk space to store the temporary files. There's no way my 4GB SSD with only 1.39MB available can ever take that, so I set the temporary directory to my SD card. You can do that by going to Edit -> Preferences -> Directories and choose a folder in your SD card to store the temporary files.

  4. Crash Recovery. Continuing the story from the 1st tip, I switched on the power supply and my Eee PC, and went into Audacity. It asked me whether I wanted to delete the temporary files. I chose NO. I then went into the temporary directory and found 638 .au files inside, about 1MB and lasting 10 secs each. If there were only a few files, I could combine them by cutting and pasting, but 638 files?? I searched and found the URLs above. The Aud_Recover command-line utility didn't work on my Eee PC and my Windows desktop PC. I gave up installing the Audacity Recovery utility on my Eee PC as it involved installing wxPython, glib, gtk+ and PyOpenGL, of which there were no simple installation instructions or packages. I almost gave up on recovering the recording. I decided to give it a last shot. I copied the 638 .au files to my external hard disk, connected it to my Windows desktop PC, installed the much-simpler-to-install Windows version of the Audacity Recovery Utility and after a few clicks and some processing time, the recording was recovered! It was not the complete sermon as the Eee PC had shutdown before it ended, but otherwise, it was a good recording. The Audacity website ( says that Audacity Beta 1.3.2 and later has automated data recovery. My current version is 1.2.4 and there is no Debian or Eee PC distribution yet for the 1.3.x versions. Once they are out, I'll probably upgrade it. Despite all these, it still proved better than the MP3 player because at least there were temporary files to recover from.

(^ v ^)

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