[MPlayer-users] Getting the best sound from mplayer

[Vladimir Mosgalin]

Hi Grant!

 On 2011.07.18 at 17:52:03 -0700, Grant wrote next:

> > 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.
> 
> Ideally, I'd like to avoid any resampling, even with
> libsamplerate_best, and any digital alteration of the audio signal
> whatsoever.

Well, realistically, these alterations introduce less distortion than
DAC process itself. Which is why they are often desired to get around
some other problem (it could be easier for DAC to convert signal sampled
at higher rate, for example).

> I think you're right that the sound is being messed up by the codec's
> downmix.  I just tried -channels 6 -af
> pan=2:.8:0:0:.8:.4:0:0:.4:.6:.6:.2:.2 and the results are great.  I
> wish I could have ALSA do that automatically for the playback of all
> audio with more than 2 channels.
> 
> Am I better of using -channels 8 and the appropriate pan config in
> case what I play has 7.1 channels?  Would a config like that work for
> 5.1 and 7.1?

I'm not sure of any good pan line for downmixing 8 to 2, sorry.. maybe
someone can suggest something. Or you can create your own, even.

> Can I have libsamplerate_best used for the downmix resampling?
> 
> If I specify -channels 6 but no pan, a lot of the sound is missing.
> Is that the equivalent of sending only the front left and right
> channels to my 2-channel DAC?

Yes.

> Isn't Blu-Ray audio always, usually, or at least sometimes 24/96?
> mplayer always lists 16/48 and the LEDs on my DAC agree.  Is mplayer
> resampling to 16/48?

Nope, it doesn't have to be of high resolution at all. I didn't meet 96
khz movie soundtrack yet, though this certainly should be possible and
maybe used for some music films or concert recordings. As for 24 bit, I
believe that loseless Blu-ray audio often contains 24 bit samples, like
DTS master audio or DD TrueHD. Though, of course, it doesn't mean that
there is any actual information past 16 bits, just because it carries
24-bit stream. Still, check out truehd track on blu-rays; mplayer
decodes it as 32-bit "s32le" so you can't really check what stream
resolution is inside (could be still 16 bit, probably), but I'm sure
that at least some of these tracks contain 24-bit audio.

-- 

Vladimir