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Upsampling to 32bit

Posted: December 11th, 2013, 5:19 am
by Ran
When playing a 24Bit / 96Khz file, MPD identifies the file correctly but according to the logs, upsamples the file:

Dec 11 00:17 : alsa_output: opened hw:CARD=Interface,DEV=0 type=HW
Dec 11 00:17 : alsa_output: format=S32_LE (Signed 32 bit Little Endian)
Dec 11 00:17 : alsa_output: buffer: size=24..131072 time=250..1365334
Dec 11 00:17 : alsa_output: period: size=12..65536 time=125..682667
Dec 11 00:17 : alsa_output: default period_time = buffer_time/4 = 500000/4 = 125000
Dec 11 00:17 : alsa_output: buffer_size=48000 period_size=12000
Dec 11 00:17 : output: opened plugin=alsa name="Wyred4Sound" audio_format=96000:32:2
Dec 11 00:17 : output: converting from 96000:24:2

Why MPD converts the bit rate from 24 to 32?

Running Ubuntu 13.10 64bit / MPD - Latest GIT version.

Re: Upsampling to 32bit

Posted: May 3rd, 2014, 8:43 pm
by scar
would also like to know why this is happening. thanks

Re: Upsampling to 32bit

Posted: May 4th, 2014, 7:33 am
by erre_erre
Converting form 24 to 32 bits is not upsampling, but probably only zero padding (no new samples are generated, since the sampling rate is the same).

Probably your soundcard interface demands 32 bits samples, as do my M-Audio Delta 1010-LT. Try to see if it happens with other sample rates and bit depths (say, 44.1/16 bits)