Regarding exporting to mono in QT Player Pro,
I though of this, but wouldn't it recompess the audio?
Probably not a problem for voice quality though.
If you are starting with compressed stereo source then
there is not currently a method that you can use to mix
down to mono directly without reencoding.
You would need to bounce the Stereo compressed
source to LPCM and then reencode, or transcode the
compressed source directly into the ultimate target
output format. If you are starting with LPCM source
then you would be able mix down from stereo (or
multichannel) source to mono.
It may be possible to use an audio editor such as Peak
to extract a single channel from a stereo encoded file
directly; but, I suspect that it would be making a bounce
to LPCM data before it actually performs the edit. Worth
checking into. They have a fully functional time limited
demo for all of their products posted on their website.
http://www.bias-inc.com/downloads/freeTrials/