[alsa-devel] Verifying mixer dB data/Invalid dB data from USB cards, especially Aureon 5.1 MkII

[Raymond Yau]

2010/2/16 Lennart Poettering <mznyfn at 0pointer.de>

> Heya,
>
>
> Invalid dB data from the driver is a real problem for the "flat
> volume" logic in PA. We basically allow each app to control the full
> hw volume range individually, and then set the hw volume to the max of
> what all apps wanted and attenuate the other streams accordingly. On
> the Aureon this doesn't work at all, since the attenuation of the
> streams is miscalculated due to the invalid dB data.
>
> Lennart
>
>
But PA also did not provide dB information to alsa application through
alsa-pulse plugin

amixer -D pulse
Simple mixer control 'Master',0
  Capabilities: pvolume pswitch pswitch-joined
  Playback channels: Front Left - Front Right
  Limits: Playback 0 - 65536
  Mono:
  Front Left: Playback 65536 [100%] [on]
  Front Right: Playback 65536 [100%] [on]
Simple mixer control 'Capture',0
  Capabilities: cvolume cswitch cswitch-joined
  Capture channels: Front Left - Front Right
  Limits: Capture 0 - 65536
  Front Left: Capture 65536 [100%] [on]
  Front Right: Capture 65536 [100%] [on]