Downmixing Surround Flac to Stereo.

[Linux for blind general discussion]

I recently downloaded a .mkv file with 5.1 audio encoded to flac and
as I inteneded to listen to it on my Blaze ET, which doesn't support
mkv files, I used mkvextract to extract the audio, producing a 1.1GB
file with roughly a 90 minute runtime. Unfortunately, My Blaze ET
apparently can't handle surround files and trying to play the flac in
ogg123 seems to only be producing sound effects.

Can anyone suggest either a means of converting the surround flac file
to stereo from the command line or suggest a lightweight command line
flac player that can properly playback surround sound files through
earphones?

-- 
Sincerely,

Jeffery Wright
President Emeritus, Nu Nu Chapter, Phi Theta Kappa.
Former Secretary, Student Government Association, College of the Albemarle.