[MPlayer-users] Movie Surround Downmixing

[Rashkae]

On 09/12/2011 05:56 AM, Nico Sabbi wrote:
> 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
>
I'll test a few like that just to see/hear the difference.  But I would 
think that would cause horrendous clipping with sound samples way over 
max amplitude.