How to detect whether OSS mixer is emulated by ALSA

How to detect whether OSS mixer is emulated by ALSA

[Christian Esken]

Hi,

my mixer (kmix) supports OSS and ALSA at the same time. This is good for a 
mixed-mode environment (e.g. if there is a TV card w/o ALSA support).

Unfortunately this means that kmix finds some mixers twice.
- One time the real thing (ALSA)
- One time the OSS-emulation

This will confuse users.

Is there any way to find out those OSS mixers which are just emulated?
I browsed http://www.alsa-project.org/~iwai/OSS-Emulation.html and other 
documentation but found nothing . I also tried to build the docs below 
alsa-doc/lib, but failed (Yes, I have openjade installed). 

Chris



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Re: How to detect whether OSS mixer is emulated by ALSA

[Paul Davis]

>Hi,
>
>my mixer (kmix) supports OSS and ALSA at the same time. This is good for a 
>mixed-mode environment (e.g. if there is a TV card w/o ALSA support).
>
>Unfortunately this means that kmix finds some mixers twice.
>- One time the real thing (ALSA)
>- One time the OSS-emulation
>
>This will confuse users.
>
>Is there any way to find out those OSS mixers which are just emulated?

check for the existence of /proc/asound and the absence of
/proc/sndstat. if the first is there and the second is not, then any
OSS mixers are emulated.

--p



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Re: How to detect whether OSS mixer is emulated by ALSA

[Jaroslav Kysela]

On Sat, 5 Apr 2003, Christian Esken wrote:

> Hi,
> 
> my mixer (kmix) supports OSS and ALSA at the same time. This is good for a 
> mixed-mode environment (e.g. if there is a TV card w/o ALSA support).
> 
> Unfortunately this means that kmix finds some mixers twice.
> - One time the real thing (ALSA)
> - One time the OSS-emulation
> 
> This will confuse users.
> 
> Is there any way to find out those OSS mixers which are just emulated?
> I browsed http://www.alsa-project.org/~iwai/OSS-Emulation.html and other 
> documentation but found nothing . I also tried to build the docs below 
> alsa-doc/lib, but failed (Yes, I have openjade installed). 

ALSA emulation layer always report the version of OSS mixer (OSS_GETVERSION) as:

#define SNDRV_OSS_VERSION         ((3<<16)|(8<<8)|(1<<4)|(0))      /* 3.8.1a */

						Jaroslav

-----
Jaroslav Kysela <perex@suse.cz>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs



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Re: How to detect whether OSS mixer is emulated by ALSA

[Christian Esken]

Am Sunday 06 April 2003 14:05 schrieb Jaroslav Kysela:
> On Sat, 5 Apr 2003, Christian Esken wrote:
> > Hi,
> >
> > my mixer (kmix) supports OSS and ALSA at the same time. This is good for
> > a mixed-mode environment (e.g. if there is a TV card w/o ALSA support).
> >
> > Unfortunately this means that kmix finds some mixers twice.
> > - One time the real thing (ALSA)
> > - One time the OSS-emulation
> >
> > This will confuse users.
> >
> > Is there any way to find out those OSS mixers which are just emulated?
> > I browsed http://www.alsa-project.org/~iwai/OSS-Emulation.html and other
> > documentation but found nothing . I also tried to build the docs below
> > alsa-doc/lib, but failed (Yes, I have openjade installed).
>
> ALSA emulation layer always report the version of OSS mixer
> (OSS_GETVERSION) as:
>
> #define SNDRV_OSS_VERSION         ((3<<16)|(8<<8)|(1<<4)|(0))      /*
> 3.8.1a */

Well, how should this help?!? It reports this value for any device, whether 
showing up duplicated or not. It doesn't help mapping ALSA mixers to 
ALSA_OSS-Mixers, does it?

For explaining things better I'll show the log of scanning 4 (sound)cards on 2 
drivers. Driver 0 (drv=0) is ALSA, Driver 1 (drv=1) is OSS:

chris@debut:~/CVS/kdemultimedia/kmix> kmix
kmix: drv=0
kmix:   dev=0
kmix:     card=0
kmix: Added one mixer: Sound Fusion CS46xx
kmix:     card=1
kmix:     card=2
kmix:     card=3
kmix:   dev=1
kmix:     card=0
kmix:     card=1
kmix:     card=2
kmix:     card=3
kmix:   dev=2
kmix:     card=0
kmix:     card=1
kmix:     card=2
kmix:     card=3
kmix: drv=1
kmix:   dev=0
kmix:     card=0
Version is: 198672
kmix: Added one mixer: Cirrus Logic CS4294 rev 5,Cirru
kmix:     card=1
kmix:     card=2
kmix:     card=3
kmix:   dev=1
kmix:     card=0
Version is: 198672
kmix: Added one mixer: Avance Logic ALC650 rev 0
kmix:     card=1
kmix:     card=2
kmix:     card=3
kmix:   dev=2
kmix:     card=0
kmix:     card=1
kmix:     card=2
kmix:     card=3
kmix: Mixers found: 3, multi-driver-mode: true

So I find
1) "Sound Fusion CS46xx" (ALSA) and 
2) "Cirrus Logic CS4294 rev 5,Cirru" (OSS-ALSA)
3) "Avance Logic ALC650 rev 0" (OSS-ALSA)

Both 2) and 3) have version "198672", but I only need to discard 2) as this
is a duplicate of 1). How should I do this?!?

Chris



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Re: How to detect whether OSS mixer is emulated by ALSA

[Paul Davis]

>Well, how should this help?!? It reports this value for any device, whether 
>showing up duplicated or not. It doesn't help mapping ALSA mixers to 
>ALSA_OSS-Mixers, does it?
>
>For explaining things better I'll show the log of scanning 4 (sound)cards on 2

although i am somewhat sympathetic to what you are trying to do, and i
agree that there should be a way to do it more easily than now, i
think that your goal is misplaced.

you need to pick an audio API, and write a mixer app that uses
it. ALSA's provision of OSS back-compatibility is not there to be used
by programs that use the native ALSA API. either use OSS, or ALSA, and
don't try both.

that's just my US$0.02, worth ever less with every bomb this country
drops on iraq.

--p


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Re: How to detect whether OSS mixer is emulated by ALSA

[Takashi Iwai]

At Tue, 08 Apr 2003 16:27:43 -0400,
Paul Davis wrote:
> 
> >Well, how should this help?!? It reports this value for any device, whether 
> >showing up duplicated or not. It doesn't help mapping ALSA mixers to 
> >ALSA_OSS-Mixers, does it?
> >
> >For explaining things better I'll show the log of scanning 4 (sound)cards on 2
> 
> although i am somewhat sympathetic to what you are trying to do, and i
> agree that there should be a way to do it more easily than now, i
> think that your goal is misplaced.
> 
> you need to pick an audio API, and write a mixer app that uses
> it. ALSA's provision of OSS back-compatibility is not there to be used
> by programs that use the native ALSA API. either use OSS, or ALSA, and
> don't try both.

yep, the easiest way would be to detect the alsa mixers at first then
run kmix as alsa-native mode if any found.  if no alsa mixer is found,
try to probe oss mixers and run in oss mode as fallback.

even if you want to mix up the both modes, the same rule is applied -
probe ALSA first then OSS.
the ALSA OSS-emulation maps the devices based on the card.
that is, the ALSA card #0 uses only /dev/mixer0 and /dev/amixer0
(for pcm, only /dev/pcm0 and /dev/apcm0).
hence, you can check the alsa cards at first, then skip the
corresponding oss devices.

but this won't work well if ALSA OSS-emulation is DISABLED and both
ALSA and OSS systems are running at the same time (yeah it's
possible), although this must be a veeery rare case.


ciao,

Takashi


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Re: How to detect whether OSS mixer is emulated by ALSA

[Christian Esken]

Am Wednesday 09 April 2003 11:19 schrieben Sie:
> At Tue, 08 Apr 2003 16:27:43 -0400,
>
> Paul Davis wrote:
> > >Well, how should this help?!? It reports this value for any device,
> > > whether showing up duplicated or not. It doesn't help mapping ALSA
> > > mixers to ALSA_OSS-Mixers, does it?
> > >
> > >For explaining things better I'll show the log of scanning 4
> > > (sound)cards on 2
> >
> > although i am somewhat sympathetic to what you are trying to do, and i
> > agree that there should be a way to do it more easily than now, i
> > think that your goal is misplaced.
> >
> > you need to pick an audio API, and write a mixer app that uses
> > it. ALSA's provision of OSS back-compatibility is not there to be used
> > by programs that use the native ALSA API. either use OSS, or ALSA, and
> > don't try both.

That's the theoretical approach - and I agree with you that this is the best 
way.

> yep, the easiest way would be to detect the alsa mixers at first then
> run kmix as alsa-native mode if any found.  if no alsa mixer is found,
> try to probe oss mixers and run in oss mode as fallback.

That's how kmix is working since some months (years?).

OK, thanks for all your feedback. So now I know I have not missed a trivial 
soulution. I'll start to think up a workaround.

Bye,
 Christian



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