2010/6/23 Colin Guthrie gmane@colin.guthr.ie
'Twas brillig, and Raymond Yau at 22/06/10 16:29 did gyre and gimble:
2010/6/22 Colin Guthrie gmane@colin.guthr.ie
As I said above, anything that comes from alsa is considered h/w amplification for the purposes of PA's volume scale. It's not practical to differentiate them
Software gain is different from hardware gain.
Really? Wow, thanks for that :p
Clipping due to software gain +12dB cannot compensated by -12dB by
hardware
atten
Another obvious statement, but not really anything to do with the discussion.
This only becomes a problem if the softvol plugin is configured to go
0dB. And if it is, then I've got to ask why....
You can configure all sorts of crazy and weird shit in alsa if you care to, but it's totally impractical for something higher in the stack to deal with all the nuances of the ultimate results of that configuration. As far as anything further up the stack is concerned, if it's represented in alsa, it's "hardware".
Just like softmodems, I don't care further up the stack whether or not the functionality is implemented in firmware or software, I just care that I have an interface to use a modem.
So, yes, of course you could configure softvol plugin to do nuts things in ALSA if you're that way inclined. I don't think anyone who is not trying to do weird things will do that, however, and I don't know of any particular h/w that is setup in a weird way by default either.
Does any card actually configure softvol, by default, to provide any gain, > 0dB for outputs? If so, then this is IMO a bad idea.
-51dB to 0dB is also software atten of softvol plugin
So that's not > 0dB then is it?
Col
As you have modified /usr/share/alsa/cards/HDA-Intel.conf
HDA-Intel.pcm.front.0 { @args [ CARD ] @args.CARD { type string } type softvol slave.pcm { type hw card $CARD } control { name "PCM Playback Volume" card $CARD }
you should notice that the front device has a softvol plugin with name "PCM Playback Volume"
why PA server still insist to open front device for capturing ?
http://thread.gmane.org/gmane.linux.alsa.devel/67912/focus=68248
As Takashi had already mention that
"I agree that the capture from "front" PCM isn't considered as valid. The "front", "rear", "center_lfe" definitions are rather for multi-channel playbacks. The capture on these channels aren't useful in most cases."
you can perform an experiement
pcm.test { type softvol slave.pcm "hw:0,0" control { name "PA Playback Volume" card 0 }
arecord -D test -f CD -d 10 -v test.wav
you will find "PA Playback Volume" in playback screen of alsamixer
I am not sure the softvol control created when PA open front device for playback and capture is used for playback or capture
BTW , PA still using "front" to open CTL device too