[pulseaudio-tickets] [PulseAudio] #580: pulseaudio master volume is scaled differently as alsa master

[PulseAudio]

#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.

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Ticket URL: <http://pulseaudio.org/ticket/580#comment:11>
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