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On my Debian machine, I was trying to extract the audio track of a video file, and then convert it to MP3.

First of all, we must take care that we allow non-free packages on our package system.

Example: /etc/apt/sources.list with Debian Wheezy

deb http://security.debian.org/ wheezy/updates main
deb-src http://security.debian.org/ wheezy/updates main

deb http://ftp.de.debian.org/debian wheezy-updates main
deb-src http://ftp.de.debian.org/debian wheezy-updates main

deb http://ftp.de.debian.org/debian wheezy main contrib non-free
deb-src http://ftp.de.debian.org/debian wheezy main contrib non-free

Then, we need to install libmp3lame0. Run this code:

aptitude update
sudo aptitude install ffmpeg libmp3lame0 libav-tools

Now, the problems came.

After this was done, I tried following:

avconv -acodec libmp3lame -i "helloworld.webm" helloworld.mp3

The result was "Unknown decoder 'libmp3lame'"

Then I tried this:

avconv -acodec mp3 -i "helloworld.webm" helloworld.mp3

Running this command, I got thousands of error messages with the content "[mp3 @ 0x1c0dc40] Header missing . Error while decoding stream #0:1" .

Finally, I found a working code:

ffmpeg -i helloworld.webm -vn -acodec libmp3lame helloworld.mp3

This finally worked, but a warning message reminds us that ffmpeg is obsolete, and instead, avconv should be used.

So, I gave it a last try:

avconv -i helloworld.webm -acodec libmp3lame helloworld.mp3

And it worked!

This is really strange: avconv does require a specific order of the parameters, otherwise it will output bogus error messages. It might be probably a bug.
Daniel Marschall
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