[alsa-devel] wrong decibel data?

Raymond Yau superquad.vortex2 at gmail.com
Thu Apr 8 01:38:25 CEST 2010

2010/4/7 Nicolo' Chieffo <nicolo.chieffo at gmail.com>

> This is what I'm doing:
> - got a jack-jack audio cable
> - connected the headphone to the mic
> - open alsamixer and put everything to 0 dB
> - verified that the pass-throw works by using the sound recorder
> ./dbmeasure plughw:0 dbmeasure_hw.log
> exits with this error:

Have you ask  the author of "dbmeasure" ?

> Iteration 1, level is 0 (-inf dB).
> Volume level measured (0) was too high or too low.
> Please adjust mixer so that initial level is between 0.8 and 0.97.
> Test run canceled.
> I've also tried to put the mic level at 100% (22.50 dB) but the output
> is the same.

your card seem to support 16/20/24bits

if you right shift your 16/24 bits digital audio by 16/24 bits , the digital
data are always zero
so any software atten on a 16/24bits sound card is still a finite negative
number dB instead of -inf  dB

that 's why the professional user prefer 32bits sound card

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