[MPlayer-users] Mplayer win32 audio to alternate output

[David Bolen]

"Brian J. Simecek" <BSimecek at InfoShare-Consulting.com> writes:

> Is there a way to send the audio from mplayer to an alternate output?  I'm
> running a dual monitor setup and have two sets of speakers connected to
> different outs on the sound card (two video's at once).  I've searched
> through the documentation and havn't found anything.

Are the two "outs" totally independent, or just different channels on
the same device?  If a completely discrete device, the dsound driver
has a device parameter that should let you control which output device
is used.

If you're instead trying to use a subset of the available channel
outputs of a single audio device (which it sounds like given that you
reference a single sound card) you may be doing something similar to
what I am.  I have a setup where we split the pair of normal stereo
output channel speakers among two screens.  I have two mplayer
instances, one for each screen.

What I do is use the channels audio filter to remap just the channel
in the source I need to the appropriate output channel (left or right)
while excluding anything else in the source.  In my case I never have
more than one source channel (generally straight through, but
occasionally reversed), but no reason you can't map multiple channels.

So for example, if I'm on the screen with the "left" speaker on the
sound card, I use something like:
    -af channels=2:1:0:0   (end with 1:1 for the source's right channel)
or if that same media was playing on the screen with the "right" speaker
it would be:
    -af channels=2:1:1:1   (end with 0:1 for the source's left channel)

I found it important to actually generate stereo output even though
only one of the channels had information or else I'd get glitches on
the other channel.

I have an additional complexity as I ended up using the win32 audio
output driver, as the default dsound driver caused audio glitches at
the end of media where the audio stream was shorter than the video.

But the win32 driver controls the master wave volume portion of the
system audio mixer, which affects all channels, so the two mplayers
would interfere with each other.

In response I stopped using mplayer for volume and instead controlled
the wave mixer volume myself, being sure to only adjust the channel I
was responsible for.

But that shouldn't be a problem if you can use dsound.

-- David