[alsa-devel] wrong decibel data?

[Raymond Yau]

2010/4/10 Nicolo' Chieffo <nicolo.chieffo at gmail.com>

> DMBEASURE
>
> There's still no way to run the measurement with "pulse" because of
> the previous error: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.
> Are you sure that the test has sense using the pulse device?
>
> "./dbmeasure plug:front plug_front.csv" works, but seems to never end:
>   Iteration 3297, level is 0.0414072 (-27.6585 dB).
>   Iteration 3298, level is 0.0414074 (-27.6584 dB).
>   Iteration 3299, level is 0.0414064 (-27.6587 dB).
>   Iteration 3300, level is 0.041406 (-27.6587 dB).
>   .....
>
>
> "./dbmeasure hw:0 hw.csv" fails with this message: "Cannot set sample
> format: Invalid argument"
>

The sum the dB range of these two hardware volume controls are already -96dB
to 0 as same as the DR of 16 bits digital audio data is 96dB

the point is that PA developer think the dB range of the pulseaudio master
volume control is -inf dB to 0dB

    control.18 {
        comment.access 'read write'
        comment.type INTEGER
        comment.count 1
        comment.range '0 - 64'
        comment.dbmin -4800
        comment.dbmax 0
        iface MIXER
        name 'Master Playback Volume'
        value 27
    }

    control.7 {
        comment.access 'read write'
        comment.type INTEGER
        comment.count 2
        comment.range '0 - 64'
        comment.dbmin -4800
        comment.dbmax 0
        iface MIXER
        name 'Headphone Playback Volume'
        value.0 64
        value.1 64
    }