[MPlayer-users] MPlayer Audio Quality

[Rich Felker]

On Wed, May 18, 2005 at 02:09:16AM +0930, Mark Williams (MWP) wrote:
> Greetings all,
> 
> Due to all the different audio media formats i play, and requiring the use of
> JACK, i use mplayer for all my music playing duties.
> 
> Im wondering how pure the audio out of mplayer is though.
> 
> For example, if i use the FLAC decoder to play music, mplayer shows it goes
> through a lot of format conversions and i assume, a couple of volume filters before it
> reaches JACK.
> 
> I assume its going through a few volume filtes as using +,- keys changes volume
> separtley to the command line volume option.
> 
> Can anyone explain the audio chain inside mplayer and how best to optimise it
> for quality?
> 
> I also just made and tried playing a simple 48khz, 32bit WAV file.
> I get this:
> 
> Playing test.wav.
> Audio file detected.
> ==========================================================================
> Forced audio codec: mad
> Opening audio decoder: [pcm] Uncompressed PCM audio decoder
> AUDIO: 48000 Hz, 2 ch, floatle, 3072.0 kbit/100.00% (ratio: 384000->384000)
> Selected audio codec: [pcm] afm:pcm (Uncompressed PCM)
> ==========================================================================
> Checking audio filter chain for 48000Hz/2ch/floatle -> 48000Hz/2ch/floatle...
> AF_pre: 48000Hz/2ch/floatle
> AO: [Jack] Initialising library.
> AO: [Jack] Sample rate mismatch, trying to resample.
> AO: [Jack] OK. I'm ready to go (44100 Hz/2 channels/16 bit)
> AO: [jack] 44100Hz 2ch s16le (2 bps)
> Building audio filter chain for 48000Hz/2ch/floatle -> 44100Hz/2ch/s16le...
> 
> Why is the audio being output to JACK at s16le when JACK can handle 32bit audio?

MPlayer doesn't do 32bit audio, and apparently your device doesn't
support 48000 Hz sampling so it gets resampled to 44100 too. Neither
of these changes is audible unless the volume of your file is
EXTREMELY low and being heavily boosted by the amp after it comes out
of the soundcard.

Rich