[MPlayer-users] Getting the best sound from mplayer

[Vladimir Mosgalin]

Hi Grant!

 On 2011.07.23 at 12:47:47 -0700, Grant wrote next:

> > I'm not sure. I don't use this one, really; maybe "default" is high
> > quality. If resampling quality isn't enough for you (which can be
> > perfectly possible, as imho lavc doesn't provide high quality resampling
> > unless you manually specify high quality options like higher filter
> > length and number of polyphase entries or linear interpolation (if you
> 
> How can I set those high quality options?

Uhh something like
lavcresample=96000:32:0:12
or
lavcresample=96000:32:1:7
are example of higher quality resampling to 96k

First example uses higher number of polyphase entries, second uses
linear interpolation instead (check lavcresample options in manpage).
Both should be "good". 

> > use it, no need to increase anything else iirc). Then again,
> > lavcresample is said to use only s16le, so your audio will be
> > downsampled to 16-bit for sure if mplayer resamples something.
> 
> Hmmm, so I can use a lower quality resampler that will leave 24-bit
> Blu-Ray audio intact, or I can use lavcresample which is a higher
> quality resampler that will convert the 24-bit audio to 16-bit?

You got me confused. I forgot, explain again please why you need
resampling in mplayer anyway?


> >> Doesn't resampling need to take place in order to downmix the 6
> >> channels to 2?  My question was meant in the context of that downmix
> >> and resampling.
> >
> > No, you can both "cut off" extra channels or do the work like pan filter
> > does in any sample rate and size. Nothing has to be resampled.
> 
> Two or more digital audio streams are combined without resampling?
> Wouldn't resampling be required in order to accomplish digital mixing
> like that?  Maybe you mean the sample rate is not changed during
> mixing?

resampling isn't required to combine two or more digital audio streams
of same sample rate. It is required when streams have different rate;
then one will have to be resampled to rate of other first, or (more
common) each has to be resampled to same common sample rate before
muxing.

pulseaudio needs base sample rate which it resamples every stream to
because it muxes audio streams with various sample rates. However, if
you only have to output single stream, you can output it with any rate
(as long as your soundcard & DAC are ok with it), without any need for
resampling.

Note that multiple resampling is always bad; which is why when you use
pulse, it always handles resampling in itself and accepts streams of any
sample rate, so another resampling won't happen in mplayer or other
application.

If you are not using pulse, however, and mplayer detect that your sound
card can only accept 48k stream (for example), it might turn on
resampling to that rate automatically (well, depends on audio driver
again, sometimes it'll be up to audio driver to behave differently). You
will see some line about that in mplayer output during playback.

-- 

Vladimir