[MPlayer-users] Getting the best sound from mplayer

[Grant]

...
>> 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.

I'm trying to implement something that will work in all situations
without me determining how many channels a video has and changing the
command line based on that before I can play it optimally.  Can I have
ALSA downmix so that all multichannel audio is downmixed using this
superior method?  I could even use libsamplerate_best with ALSA.

If not, is there any way to select a higher quality resampling than
the default in mplayer?

>> 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.

I tried this:

mplayer -channels 6 -ao alsa:device=plughw=0.0 -format s24le title.mkv

but got the same results with missing sound.  Shouldn't ALSA downmix
the 6 channels to 2 if I specify plughw like this?

>> 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.

Does mplayer resample to 16/48 regardless of the source's sample size and rate?

- Grant