#580: pulseaudio master volume is scaled differently as alsa master
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Reporter: yelo3 | Owner: lennart
Type: defect | Status: reopened
Milestone: | Component: module-alsa-*
Resolution: | Keywords:
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Comment(by yelo3):
Another quote from the alsa bug
Refer to HD audio specification
The theoretical possible maximum dB range of HDA codec is -32dB/step x
128step = -4096dB which is much larger than -inf dB and 0dB is defined by
the offset
, so it is wrong for PA developer to assume the minimum dB of the HDA
codec volume control is -inf dB
7.3.4.10 Amplifier Capabilities
The “Amplifier Properties” parameters return the parameters for the
input
or the output amplifier on a node. In the case of a Pin Widget, the terms
input
and output are relative to the codec itself; for all other widgets, these
terms
are relative to the node. The amplifier capabilities are indicated by the
step
size of the amplifier, the number of steps, the offset of the range with
respect to 0 dB, and whether the amplifier supports mute.
StepSize (7 bits) indicates the size of each step in the gain range.
Each
individual step may be
0-32 dB specified in 0.25-dB steps. A value of 0 indicates 0.25-dB
steps,
while a value of 127d indicates a 32-dB step.
NumSteps (7 bits) indicates the number of steps in the gain range.
There
may be from 1 to 128 steps in the amplifier gain range. (0d means 1 step,
127d
means 128 steps). A value of 0 (1 step) means that the gain is fixed and
may
not be changed.
Offset (7 bits) indicates which step is 0 dB. If there are two or
more
steps, one of the step values must correspond to a value of 0 dB. The
“Offset”
value reflects the value which, if programmed in to the Amplifier Gain
control,
would result in a gain of 0 dB.
Mute Capable (1 bit) reports if the respective amplifier is capable
of
muting. Muting implies a –infinity gain (no sound passes), but the actual
performance is determined by the hardware.
--
Ticket URL: <http://pulseaudio.org/ticket/580#comment:11>
PulseAudio <http://pulseaudio.org/>
The PulseAudio Sound Server
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