All you need is a version of the Open Source software Media Coder. Just download and install the version and start the program afterwards. The easiest way is to drag and drop video files into the main window and select them by left-clicking them.

Once that is done you have to choose transcode from the menu and select Transcode Audio Only from it. This rips the audio of the video file and saves it in the same directory.

You may want to make sure that all settings are correct before you start your first transcoding. The first thing that you should do is to click on the Audio tab and make sure that all settings there are the way you want them to be. I suggest that you use the lame mp3 encoder but you could select another one installed on your computer.

It is possible to normalize the audio and resample it as well. The default transcoding bitrate is 128 Kbit which can be changed in the Lame tab by raising the quality bar.

Multiple video files can be processed in batch mode. Just drag and drop everything into the main window and perform the same actions that are valid for a single process.