[alsa-devel] Handling of the DXS controls in the via82xx driver
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 [http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.32.y.git;a=commit...], 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 3d00941371a765779c4e3509214c7e5793cce1fe [http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.33.y.git;a=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
Sören
2010/3/28 Soeren D. Schulze soeren.d.schulze@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 [ http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.32.y.git;a=commit... ], 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 3d00941371a765779c4e3509214c7e5793cce1fe [ http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.33.y.git;a=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
Sören
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
2010/3/28 Soeren D. Schulze soeren.d.schulze@gmx.de
Hi everyone,
amixer cset numid=47,iface=PCM,name='PCM Playback Volume' 24,24
When restarting mplayer, the volume is reset to 31,31 (maximum). Commit 3d00941371a765779c4e3509214c7e5793cce1fe [ http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.33.y.git;a=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.
Sören
In theory , the driver should reset the per voice volume control to 0dB after the subdevice is opened , may be something wrong in dB scale of these volume control if you get distorted sound
Soeren D. Schulze wrote:
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.
As I'm not an ALSA developer, I don't realize the intended effect of this change,
Hiding these controls is an intended effect, because normal mixers do not show application-specific controls that could go away or be reset at any time.
but the actual effect is that I cannot change the DXS volumes any more.
You can with the hwmixvolume tool in the alsa-tools package (version 1.0.23, not yet released).
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).
The old behaviour was considered buggy: these stream controls are logically associated with a stream opened by an application, not with a particular hardware stream.
The bad thing about it is that 31,31 is a really bad setting for my poorly engineered sound card. It distorts a lot.
If the card cannot handle any loud output, then all outputs from any source must be restricted, so the logical place for lower volume would be the "Master" or "PCM" controls.
Regards, Clemens
Clemens Ladisch wrote:
The bad thing about it is that 31,31 is a really bad setting for my poorly engineered sound card. It distorts a lot.
If the card cannot handle any loud output, then all outputs from any source must be restricted, so the logical place for lower volume would be the "Master" or "PCM" controls.
The problem is rather that it cannot handle loud *input*. With loud input from digital plus the respective DXS lever on high volume, it apparently overdrives at a very early stage in the sound card. Master and PCM do not help anything any more.
The other workaround would probably be using softvol for reducing the volume before it enters analog, but lowering the DXS levers is still better IMHO.
Thank you
Sören
2010/3/29 Soeren D. Schulze soeren.d.schulze@gmx.de
Clemens Ladisch wrote:
The bad thing about it is that 31,31 is a really bad setting for my poorly engineered sound card. It distorts a lot.
If the card cannot handle any loud output, then all outputs from any source must be restricted, so the logical place for lower volume would be the "Master" or "PCM" controls.
The problem is rather that it cannot handle loud *input*. With loud input from digital plus the respective DXS lever on high volume, it apparently overdrives at a very early stage in the sound card. Master and PCM do not help anything any more.
The other workaround would probably be using softvol for reducing the volume before it enters analog, but lowering the DXS levers is still better IMHO.
Thank you
Sören
did you set those per voice volume control to 0dB ?
try to play a sine wave of full amplitude and record using analog loopback of ac97 codec and audacity to find out whether the sine wave is clipped
2010/3/29 Clemens Ladisch clemens@ladisch.de
Soeren D. Schulze wrote:
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).
The old behaviour was considered buggy: these stream controls are logically associated with a stream opened by an application, not with a particular hardware stream.
The bad thing about it is that 31,31 is a really bad setting for my poorly engineered sound card. It distorts a lot.
If the card cannot handle any loud output, then all outputs from any source must be restricted, so the logical place for lower volume would be the "Master" or "PCM" controls.
Regards, Clemens
Correct me if I am wrong , ac97 codec support 16,18,20 bits resolution and the ac97 specification mention that if a sample stream of resoultion is less than 20 bits is transferred through ac97 link, the ac97 controller must stuff all trailing invalid bits with zero.
This mean that the ac97 controller can provide a maximum of 12 dB gain if your codec support 20 bits resolution , any gain over 12dB by the ac97 controller will lead to clipping
participants (3)
-
Clemens Ladisch -
Raymond Yau -
Soeren D. Schulze