[MPlayer-users] Movie Surround Downmixing

[Nico Sabbi]

Rashkae ha scritto:
> I've noticed that an increasing number of videos have their sound
> recording levels such that speech often gets drowned out by
> surrounding sound/noise.  And if volume is increased to levels where
> it's easy to hear what actors are saying, the volume of everything
> else will seem disproportionately loud.  With some research, I've
> found that the common wisdom is to increase the volume of the center
> channel of your surround system.  Not such an easy feat with 2 speaker
> sound system/headphones.
>
> After studying Mplayer documentation and source code, I've come with
> the following options:.
>
>
> -channels 6 -af pan=2:0.4:0:0:0.4:0.2:0:0:0.2:0.5:0.5:0.1:0.1
>
> (Note, the mplayer default for downmixing puts the volume level of
> center channel at .3, here I've boosted that to .5)
>
> In theory, increasing the volume of center channel without decreasing
> everything else runs the risk of total volume being too high and sound
> clipping as a result.  In practice, every soundtrack I've tested has
> more than enough headroom for this extra boost and overall, sounds
> much better in stereo.  I believe this is what most set top dvd/bd
> players do when playing Surround to stereo.
>
> Question: Any more experienced mplayer users/devs have different insight?
>
>
> Suggestion: If this problem is something that affects people (besides
> myself), it might be good to have an option to boost center channel
> when downmixing.  Manually tweaking the pan filter isn't really
> something I would expect people to do who just want to watch a movie.

I always use
-af pan=2:1:0:0:1:1:0:0:1:1:1:1:1

that is, all that is left goes to the left and all that is right goes to 
the right. All else goes to both.
Dumb, but much better for me.