[pulseaudio-discuss] Alsamixertest

Colin Guthrie gmane at colin.guthr.ie
Wed Sep 29 03:24:29 PDT 2010

'Twas brillig, and David Henningsson at 29/09/10 10:19 did gyre and gimble:
> Hi Colin,
> for some reason your test of alsamixertest didn't reach me the normal
> path, so I'm pasting it in from the archives:

Strange... Seems to be on gmane.org so not quite sure where it could
have disappeared to. Hey ho.

>> What license do you use.
>> Couldn't seem to find any reference to it...
> It should be GPLv3, thanks for noticing.

No worries.

>> Ultimately the results seem to indicate that "Master" is OK,
>> but out by a bit,
> Yeah, I have seen that on one of my test machines here as well, and I
> don't know if one should mark that as error, I probably shouldn't. I
> don't even know if that's a volume control or an ADC problem in that case.

The values are not crazy ridiculous, so I'm not overly worried about
them, but it is interesting to note.

>> but PCM is all kinds of broken.
> PCM is indeed very broken. I've traced it down to alsactl as well, and
> if the decision was mine, I would remove it right away, but upstream
> wasn't convinced. :-( See the long thread starting at
> http://mailman.alsa-project.org/pipermail/alsa-devel/2010-August/031054.html

Ahh thanks. I didn't catch that the first time round. Interesting read.

It doesn't sound like there is a solution yet.

Could the problem be simplified: when PCM isn't really needed, just make
the volume range something very small like 1dB (currently mine has a
51dB range). In PA we can just check the range of any element and if
it's stupidly small, we can ignore it.

Would that work? Is it worth taking this suggestion to the alsa folks?

>> FWIW, the testing for -18.0, expected -21.04 measure -20.03dB is all a
>> little confusing. When testing for -18.0, why is 021.04 expected?
>> Perhaps some more explanation would be nice as to why the expected
>> values differ from the test value.
> So when it did the initial testing signal, it set everything to 0 dB and
> the input signal received was -3.04 dB. So when setting Master to -18
> dB, it expects the input signal to be -18-3.04 = -21.04 dB.

Right and that's why the PCM results always reported ~-3dB too (as PCM
was essentially "inactive" despite reporting that it is used.



Colin Guthrie

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