Fast-forwarding through screencasts without ant voice

One thing that always stopped me from using screencasts as a viable learning tool is that they usually take too long. And most of the time it’s the guy moving around, or saying “uh”, “er…”, or doing stuff I already know. And when I tried skipping a few seconds ahead I usually skipped the very few meaty bits and had to go back and listen to them again. So what I did sometimes was increasing the playback speed (by pressing the ]-key on mplayer), but that made the guy speak as if breathing helium.

Not anymore!

Mplayer (from svn) has a fantastic new audio filter called scaletempo. It basically lets you change the playback speed without changing the sound pitch. The guy speaks faster, but in the same tone. Isn’t that amazing?! So, here’s how to do it (you really need the svn version as of now; 1.0rc2 won’t do it) on Ubuntu:

First, we need to install the dependencies for compiling the new package (without installing the package itself):

sudo apt-get build-dep mplayer

Now the usual checkout, compile and install:

cd /tmp
svn checkout svn://svn.mplayerhq.hu/mplayer/trunk mplayer
cd mplayer
./configure
make
sudo make install


And that’s it! Now you just open your videos like this:

mplayer screencast.ogm -af scaletempo

and use the keys [ and ] to adjust playback speed at will.

Edit: from my experience, you can speed up speech up to 1.5-1.75 without losing quality. That means you can watch a 1-hour video in 34-40min!