[alsa-devel] Handling of the DXS controls in the via82xx driver
superquad.vortex2 at gmail.com
Mon Mar 29 03:24:33 CEST 2010
2010/3/28 Soeren D. Schulze <soeren.d.schulze at gmx.de>
> Hi everyone,
> before my latest upgrade to Linux 2.6.32 (yes, sorry, it's Debian), I
> had four levers in my alsamixer: VIA DXS, VIA DXS 1, VIA DXS 2 and VIA
> DXS 3. They controlled the hardware mixing when accessing the sound
> device multiple times.
> Now they have disappeared. I think I can pretty certainly trace this
> down to commit 2fb930b53f513cbc4c102d415d2923a8a7091337 to Linux
> which "move[s] DXS volume controls to PCM interface".
> As I'm not an ALSA developer, I don't realize the intended effect of
> this change, but the actual effect is that I cannot change the DXS
> volumes any more. mplayer still controls the global PCM volume. Well,
> in fact, there is one way. While an mplayer is running, I can do:
> amixer cset numid=47,iface=PCM,name='PCM Playback Volume' 24,24
> When restarting mplayer, the volume is reset to 31,31 (maximum). Commit
> seems to be responsible for this.
> The bad thing about it is that 31,31 is a really bad setting for my
> poorly engineered sound card. It distorts a lot.
> I suspect that the real *bug* is that mplayer does not use the
> per-channel DXS controls even though it's supposed to (which seems to be
> why the DXS controls are called "PCM Playback Volume").
> Personally, rather than fixing this bug, I would just revert to the
> former state. I was always happy with all the DXS levers set to 75%.
> Thank you
Those are per voice volume control , they can be used for the hardware
acclearation in wine if wine implmenet the real hardware acceleration
After this change , they are not used by the mixer any more , only those
application which open those subdevices can find the corresponding control
by the subdevice number
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