Tuesday, November 10, 2009

Optimizing mplayer for interview transcriptions

Yes, transcribing interviews is a pain! But there are several thing you can do on a Unix system that can help you ease the pain.

Although there exists a software out there that is even supposed to work with a pedal: Express Scribe by Australian company NCH Software - which works natively or as a Windows binary with wine, I chose mplayer. First and foremost because scribe didn't load the WMA files produced by my voice recorder.
Interestingly enough though, NCH Software describe a couple of ways to use their software with a pedal, and even offer tips on 'DIY' foot pedal solutions and they also have a documentation on "Writing a driver for an unsupported controller" (for Windows though).

There's a couple of tweaks and treats you can do to optimize mplayer for such a task. The most obvious at first seemed to reduce the playing speed, which can be done in every mplayer installation by the default keys "[" and "]".

To keep the same pitch of the voices however, you'll have to use an audio filter, that is by now part of every standard installation: scaletempo

Which brings us to the following command:
~ $ mplayer -af scaletempo
Now there is one remaining problem, namely the left and right buttons on your keyboard, in their default confirguration, do rewind or fastforward your file by 10 seconds. That is way too far when transcribing interviews.
Luckily, this can be configured as well. What you'll have to do is create a file in your .mplayer directory that holds a new configuration for the right and left keys. I.e.:
~$ cat ~/.mplayer/transcribe
RIGHT seek +3
LEFT seek -3
Now if you start mplayer while passing it that file as input configuration, your directional keys will seek by 3 seconds instead of 10. You might want to add an alias to you bashrc that says

alias transplayer="mplayer -af scaletempo -input conf=transcribe $1"
After sourcing that file, you may then use your customized setup by invoking "transplayer" at the cli:

~ $ source ~/.bashrc
~ $ transplayer

Of course, more than just the right or left keys can be reconfigured. To get an idea of what commands and keys are available, you may use

~ $ mplayer -input cmdlist
~ $ mplayer -input keylist

For more information on customizing your mplayer setup, please RTFM ;)

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