[MPlayer-users] Getting the best sound from mplayer

[Vladimir Mosgalin]

Hi Grant!

 On 2011.07.17 at 18:18:39 -0700, Grant wrote next:

> Blu-Ray rips in mplayer.  I've tried:
> 
> mplayer -ao alsa:device=hw=0.0 -format s24le video.mkv

There is no real need to use hw devices at all. If you are trying to do
that only to pursue clean audio, you are doing something wrong.

default device should work just as well, providing that you have dmix
turned off. At very least, plughw device should work at least as good.
If you want to ensure max resolution and audio quality, I suggest you to
use pulseaudio. In mplayer, -ao pulse will always do ouput at stream
resolution and with floatle samples, which is best it's possible to get,
quality-wise, and at pulseaudio you can set up once and for all to
output at max sample size and highest resolution that your card support,
with some high quality resampler.

> but the result sounds like it's been altered by dmix or a software
> volume control or another digital alterer.  I think the problem
> doesn't exist with DVD rips.  Does anyone know why this is happening?

You should explain in more detail what you are talking about. Also, does
the problem persist with plughw? With pulse?

> I'm also curious about the downmix from 6-channel audio in a Blu-Ray
> rip for my 2-channel USB DAC.  Does that take place in mplayer or
> elsewhere?

In mplayer. This is probably where you lose most quality, anyway. If you
are forced to listen to multichannel signal on stereo system, the
default resampler might not be what you desire. Mplayer supports
downmixing for headphones (use -channels 6 -af volume=-5,hrtf. If you
hear cracking of sound at loud scenes, use bigger volume reduction, like
volume=-10,hrtf) and you can emulate various multichannel-to-stereo
conversion formulas, like
-af pan=2:0.4:0:0:0.4:0.2:0:0:0.2:0.3:0.3:0.1:0.1
or
-af pan=2:0.4:0:0:0.4:0.2:0:0:0.2:0.2:0.2:0.2:0.2
or some others.

If you desire better quality and can't use multichannel for some reason,
probably your only hope is multichannel receiver which will accept all 6
channels from mplayer (unlike current stereo DAC) and convert them to
stereo, emulating some kind of room and such. These things can be pretty
configurable and can give pleasant results. This affect sound in movies
much more than making sure you are using 32-bit samples and such; all
talk about "purest audio" is kind of meaningless if you have to convert
multichannel to stereo, that's where you lose most of information
anyway.
(note that you will need HDMI complaint receiver and sound card to get
multichannel audio from blu-ray on the PC properly)

-- 

Vladimir