[MPlayer-users] possible to send mono sound to just one speaker?

[Corey Hickey]

Alec Bennett wrote:
> Thanks, that's progress. This line sends audio to only one of the speakers:
> 
> -af pan=2:1
> 
> The problem is, I can't figure out the pan filter. I can't really find any
> docs on it. This is the closest I found:
> 
> http://www.mplayerhq.hu/DOCS/HTML/en/advaudio.html

It's difficult, I admit. Do you have any suggestions as to how I could
improve that document?

I think you might be getting confused by this particular example. In
order to hear a mono file in one channel, you need to make two channels
out of it, which seems rather strange at the outset.

1. When mplayer outputs mono sound, the sound card (or the driver?)
automatically sends the same channel to both speakers.
2. If mplayer outputs two channels instead, the channels are each played
on their respective speakers.
3. If one of those channels contains silence, then you'll only hear a
single speaker.

The pan example you gave above is actually short for pan=2:1:0. Missing
parameters at the end default to 0. 2:1:0 means:
- two output channels
- the input channel is mixed 100% into the first (left) output channel
- the input channel is mixed 0% into the second (right) output channel

As Alec Benett pointed out, 2:0:1 will play to the right speaker.


Normally I would recommend using the channels filter instead of pan, for
moving entire channels around without mixing, but in this case the
syntax is actually longer:
Left  speaker -- channels=2:1:0:0  (shortens to channels=2:1)
Right speaker -- channels=2:1:0:1


-Corey