[MPlayer-users] A plea for LFE-help (solution)

[Adam Nielsen]

> The manual describes the pan- and channels audiofilters in a very
> abstract way, and that is what my plea for help is about.

It's not *that* bad ;-)

> By following (or trying to follow) the instructions in the manual I don't
> get this to work, that is why I asked if someone has managed to do what I
> want and could share their mplayer configuration with me..

Well, having never tried this before I just had a read of the manpage and got 
it working myself, so I'll try to explain it in a little more detail for you.  
Here goes ;-)

The pan command looks like this (spaced out so you can see it more easily.)

-af pan= num : FL:FR:RL:RR:CTR:LFE

Where num is the number of incoming channels (5.1 == 6 incoming channels) and 
FL is front left, FR is front right, etc.  Use zero for no mix or 100 for 
full mix (any non-zero value seems to have the same effect.)  This will 
become clearer further down.

You then repeat the whole FL:FR bit for every output channel - so if you're 
outputting stereo, you'll repeat it twice:

-af pan= num : [left-channel] : [right-channel]

Then, replace [left-channel] with the mix values:

  FL :FR:RL :RR:CTR:LFE
  100:0 :100:0 :100: 0

This means that the mix for the left channel will contain the Front Left, the 
Rear Left and the Centre channel.  If you replace [left-channel] with this 
(removing the extra spaces of course) then you'll get this front+rear left 
mix coming out of the left channel.  If you replace [right-channel] then 
obviously it'll come out of the right-channel instead.

So if that's the value for left, you'd probably want this for the 
right-channel:

  FL:FR :RL:RR :CTR:LFE
  0 :100:0 :100:100: 0

If you want the LFE included into the mix, then mix that value in as well:

  FL:FR :RL:RR :CTR:LFE
  0 :100:0 :100:100:100

Then join them all together, remove the spaces and you should have something 
similar to this:

  [left-channel] is 100:0:100:0:100:0
  [right-channel] is 0:100:0:100:100:100

Therefore:

  -af pan= num : [left-channel] : [right-channel]

becomes:

  -af pan=6:100:0:100:0:100:0:0:100:0:100:100:100

Which you use like this:

  mplayer filename -af pan=6:100:0:100:0:100:0:0:100:0:100:100:100


And that will mix all the channels into a stereo output.  You won't get Dolby 
surround like this (the rear channels will go out of their corresponding 
front ones (like the probably already do), they won't be converted into a 
mono channel that sounds like it's coming from behind you.)

You said that everything works fine except for the LFE, but you'll still need 
to mix in the rear+centre inputs I think, because once you start outputting a 
stereo signal your sound card won't mix the rear channels in for you any 
more.  Anyway, try fiddling with the mix amounts and see what you come up 
with.

If you find something you're happy with, you can add it to your config file 
(~/.mplayer/config):

af=pan=6:100:0:100:0:100:0:0:100:0:100:100:100

Cheers,
Adam.