FFmpeg imports mono tracks as stereo[SOLVED]

for saving space and before conversion to AAC by FFMPEG. very easy in principle, looking here http://wiki.audacityteam.org/wiki/Talk:Mixing_stereo_tracks_to_mono_in_your_Project
still, if I save the mono track and re-open it I still se two channels. I cannot fine any oprion which sets the mono bit in the AAC file
If i do the same using the mp3 lame encoder I can see just one track in audacity when re-reading the saved fil
thanks for your help
I am 2.x and W7

To convert a stereo track to mono in Audacity 2.x,
Select the track, then “Tracks menu > Stereo Track to Mono”

…for saving space and before conversion to AAC by FFMPEG.

I wouldn’t want a “fake” stereo file, but I don’t think you’ll save space by saving a mono file as mono AAC. AAC uses [u]Joint Stereo[/u] by default, which encodes the L+R & L-R signals separately. With mono, there is no sound in the L-R “channel”, and AAC (and MP3) are “smart enough” not to waste space when there is nothing to encode, so you are only encoding one channel’s worth of information.

Update to the currently recommended FFmpeg 0.6.2 ( http://manual.audacityteam.org/o/man/faq_installation_and_plug_ins.html#ffdown ) then it will import mono AAC files as mono.


thanks, it works! and yes, saving mono files will save 50% of space approx (as expected)