Transcode and cache audio only from video

[ramschel]

I like to listen to the audio of movies while I drive. Since I am not watching the video, there isn't a need to take up bandwidth and memory to keep that stream of the file. In the past I have manually extracted the audio stream of movies and then encoded them as MP3 for listening on the road. It seems like this could be streamlined with Subsonic into one step of picking a movie and then choosing to transcode/cache the audio only. Thank you for considering this.