[MPlayer-users] Surround Decoding on AC3: 2.0 (stereo) and AC3: 2.0 (dolby)

[Alexander Roalter]

As I recently found out, using -af surround enables the surround 
decoding abilities of mplayer even for Dolby Surround tracks (2.1). This 
was not possible on my older system, where I only used -channels 6, but 
with my (non-onboard) Sound card (Terratec something, still AC97) I have 
to use -af channels=6 too.
Appending -af surround to this does the trick, and playing 5.1 sound 
everything is decoded just fine, and playing dolby surround encoded 
material, the rears and the center are fed appropriately with material.

But when playing stereo (without the surround marker), the decoder is 
still applied, and I hear the voices, which should only come from the 
center speaker (or front left&right) also from the rears, which is very 
distracting.

As this is probably intended to apply the decoding even to incorrectly 
flagged audio streams, I'd like to know if there's an automatic way of 
turning this off on plain stereo tracks - sort of
-af surround_only_when_flagged_as_surround

Otherwise one would always have to specify -af surround only on dolby 
surround tracks and leave it out otherwise... :(

cheers,
Alex