2010/5/27 Colin Guthrie gmane@colin.guthr.ie
'Twas brillig, and Clemens Ladisch at 27/05/10 14:48 did gyre and gimble:
Colin Guthrie wrote:
state.Intel { control.1 { comment.access 'read write' comment.type INTEGER comment.count 2 comment.range '0 - 31' comment.dbmin -4650 comment.dbmax 0 iface MIXER name 'Master Playback Volume' value.0 30 value.1 30 }
This is the hardware volume control.
control.11 { comment.access 'read write user' comment.type INTEGER comment.count 2 comment.range '0 - 255' comment.tlv '0000000100000008ffffec1400000014' comment.dbmin -5100 comment.dbmax 0 iface MIXER name 'PCM Playback Volume' value.0 253 value.1 253 }This is the emulated software volume control that is created by the softvol plugin. This control gets recreated by "alsactl restore" even when the plugin is not running.
Might it be possible that PA is trying to use this, but that it doesn't have any effect because PA is using PCM device hw:0? (Try unloading snd-hda-intel and then deleting that entry from /etc/asound.state.)
PA should play nice with the softvol plugin so I don't think this is the bit that is at fault.
For AC97 codec
PCM -34.5dB to +12 dB Master -46.5dB to 0dB
The total dB range is -81dB to +12dB
For HDA
No idea how to know the master volume control is a virtual master volume control
The softvol plugin -51dB to -0dB is software atten of the input digital signal before pass to the HDA sound card
PA seem has its own software atten/gain and mixing of the digital signal from the PA clients
I strongly suspect that the reason has already been correctly identified a while ago, which is that this card considers -48dB silent where as PA assumes this level is -200dB. I believe it was Raymond who pointed out the -48dB level in the HDA spec before on this list.
Different HDA codecs have different dB range according to the HDA spec
I'm not sure of the internals, but things do indeed go silent when the volume reaches the magic -48dB mark (which is around the 14% mark with the current cubic mapping).
I suspect that if I were to define infinity to be 48.0 in PA, everything would work nicely.
I have doubt since I can still hear sound when using ac97 codec of my au8830 below -48dB and using baudline (require OSS emulation) also indicate that there is signal recorded by using loopback of ac97 codec
What I think is then ultimately needed is a way to ensure that everyone sings from the same hymn sheet regarding the real world value of -inf dB.
I was hoping Lennart would have commented on this thread by now, so I'll try and prod him to get some proper input as I'm very much flailing around wildly in the dark!
Col