I want to have as long (minutes of playing time) an mp3 as will fit on a standard 700MB CD-R. The rub is that I want this mp3 to be silent - no audio information at all. I just want it to play silence for as long as possible.

I'm assuming I'll be able to make an arbitrarily long silent .wav file as a source.

This leaves two questions, how do I compress this .wav file for maximum data density (longest play time)? Secondly once I know how to encode the .wav file, how long must it be pre-encoding to fit (within a few MB) on an 700 MB CD?

An odd request, but here's the why of it:

The 2005 Subaru Legacy/Outback has a nastily integrated stock stereo with no AUX input. People have figured out how to hardware hack line level into the CD audio path. This requires playing a silent CD while really playing your Aux source. My Outback has the stereo with MP3 capability, so I want to have as long a CD as possible. The non-MP3 head units mute briefly every 72 minutes as the CD mechanism repeats. I want to maximize the time between these brief mutes by using a hyper long silent MP3 track.

Thoughts?

-Zeke