Standard mixer control names

Standard mixer control names

[Lennart Poettering]

Heya!

I'd like to add functionality to PulseAudio to allow a simplified
selection of capture input (i.e. "Mic", "Line-In", ...) and playback
outputs ("Headphones", "Line-Out", ...) for ALSA cards. By
"simplified" I mean that only one input and output shall be active at
a time. Also, some more nonsense items shall be filtered out
(i.e. recording from "Phone"). Hence, basically I want to compile a
list of available and whitelisted inputs and outputs and allow the
user to select exactly one from each.

ALSA is making that very hard to implement something like this because
every driver seems to wrap input/output selection differently.

On one card I have only has a couple of cswitches
(snd-es1371). The same one has an enum "Mic Select". Another card has
an enum "Input Source", but no cswitches (a HDA chip). The
"ControlNames.txt" file in the kernel seems to suggest that there is an
element "Capture Source".

For playback it seems that some cards have a a headphone switch, and
others a headphone slider (which i guess makes sense).

Now, the question, how should I implement this?

For playback the handling is easy as long as there is only one element
to deal with, but what about capture? One option would be to simply
go by cswitch and nothing else. Or go by "Input Source" and nothing
else. Or combine some form. Now I'd of course prefer if the drivers
get fixed to use a single element naming scheme only. Is there any
chance to get that? And which one would that be?

Lennart

-- 
Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net         ICQ# 11060553
http://0pointer.net/lennart/           GnuPG 0x1A015CC4

Re: Standard mixer control names

[Liam Girdwood]

On Sun, 2009-02-22 at 00:36 +0100, Lennart Poettering wrote:
> Heya!
> 
> I'd like to add functionality to PulseAudio to allow a simplified
> selection of capture input (i.e. "Mic", "Line-In", ...) and playback
> outputs ("Headphones", "Line-Out", ...) for ALSA cards. By
> "simplified" I mean that only one input and output shall be active at
> a time. Also, some more nonsense items shall be filtered out
> (i.e. recording from "Phone"). Hence, basically I want to compile a
> list of available and whitelisted inputs and outputs and allow the
> user to select exactly one from each.
> 

Fwiw, I may have mentioned at the FOSDEM beer party that this feature
was on the to todo list for the hardware use case or scenario manager.
Although being a beer party we may not remember discussing....

http://www.slimlogic.co.uk/?p=40

>  Now I'd of course prefer if the drivers
> get fixed to use a single element naming scheme only. Is there any
> chance to get that? And which one would that be?
> 

This would likely be quite time consuming wrt to embedded drivers due to
the complex audio hardware requirements of modern mobile phones. There
are numerous hardware routes with different inputs and outputs and they
are used in different combinations depending on use case.

I think it's probably quite reasonable to do this for most PC sound
cards as they are often simpler in terms inputs/outputs.

Liam

Re: Standard mixer control names

[Mark Brown]

On Sun, Feb 22, 2009 at 12:00:12PM +0000, Liam Girdwood wrote:
> On Sun, 2009-02-22 at 00:36 +0100, Lennart Poettering wrote:

> >  Now I'd of course prefer if the drivers
> > get fixed to use a single element naming scheme only. Is there any
> > chance to get that? And which one would that be?

> This would likely be quite time consuming wrt to embedded drivers due to
> the complex audio hardware requirements of modern mobile phones. There
> are numerous hardware routes with different inputs and outputs and they
> are used in different combinations depending on use case.

I'd worry that it'd also have a negative impact on usability.  People
setting up scenarios and doing other device specific configuration
often find it difficult to relate the controls visible in ALSA to the
chip datasheet and keeping the names for the controls as close as
possible to the datasheet helps deal with that quite a bit.  If a
standard naming were layered on top by something like the scenario
manager this wouldn't be such an issue since device specific names would
still be there and controls could be remapped dynamically depending on
use case.

What would probably also help would be exposing information about the
audio paths and how they relate to controls to user space but that
doesn't look likely to happen any time soon.

Re: Standard mixer control names

[Liam Girdwood]

On Sun, 2009-02-22 at 12:56 +0000, Mark Brown wrote:
> On Sun, Feb 22, 2009 at 12:00:12PM +0000, Liam Girdwood wrote:
> > On Sun, 2009-02-22 at 00:36 +0100, Lennart Poettering wrote:
> 
> > >  Now I'd of course prefer if the drivers
> > > get fixed to use a single element naming scheme only. Is there any
> > > chance to get that? And which one would that be?
> 
> > This would likely be quite time consuming wrt to embedded drivers due to
> > the complex audio hardware requirements of modern mobile phones. There
> > are numerous hardware routes with different inputs and outputs and they
> > are used in different combinations depending on use case.
> 
> I'd worry that it'd also have a negative impact on usability.  People
> setting up scenarios and doing other device specific configuration
> often find it difficult to relate the controls visible in ALSA to the
> chip datasheet and keeping the names for the controls as close as
> possible to the datasheet helps deal with that quite a bit.  If a
> standard naming were layered on top by something like the scenario
> manager this wouldn't be such an issue since device specific names would
> still be there and controls could be remapped dynamically depending on
> use case.
> 

Standard naming just got added to the scenario manager todo list !
It's really just an extension of the control aliasing we talked about
earlier.

Liam

Re: Standard mixer control names

[Takashi Iwai]

At Sun, 22 Feb 2009 00:36:30 +0100,
Lennart Poettering wrote:
> 
> Heya!
> 
> I'd like to add functionality to PulseAudio to allow a simplified
> selection of capture input (i.e. "Mic", "Line-In", ...) and playback
> outputs ("Headphones", "Line-Out", ...) for ALSA cards. By
> "simplified" I mean that only one input and output shall be active at
> a time. Also, some more nonsense items shall be filtered out
> (i.e. recording from "Phone"). Hence, basically I want to compile a
> list of available and whitelisted inputs and outputs and allow the
> user to select exactly one from each.
> 
> ALSA is making that very hard to implement something like this because
> every driver seems to wrap input/output selection differently.
> 
> On one card I have only has a couple of cswitches
> (snd-es1371). The same one has an enum "Mic Select". Another card has
> an enum "Input Source", but no cswitches (a HDA chip). The
> "ControlNames.txt" file in the kernel seems to suggest that there is an
> element "Capture Source".

That's because "Capture Source" can't work for multiple (sub)devices
with the mixer abstraction of alsa-lib, per design.
"Input Source" was born as a workaround (still found in many places
in the driver code).  Maybe we should update ControlNames.txt as well.

> For playback it seems that some cards have a a headphone switch, and
> others a headphone slider (which i guess makes sense).
> 
> Now, the question, how should I implement this?
> 
> For playback the handling is easy as long as there is only one element
> to deal with, but what about capture? One option would be to simply
> go by cswitch and nothing else. Or go by "Input Source" and nothing
> else. Or combine some form. Now I'd of course prefer if the drivers
> get fixed to use a single element naming scheme only. Is there any
> chance to get that? And which one would that be?

I rarely believe this will be ever "fixed" in the driver side
completely.  We may improve a bit, but not the whole stuff.
It's no good idea to have a restriction in the driver code because
the control API is just for generic purpose, not only about mixers.
And, many embedded devices love to have specific unique control names
just for their purpose...


Takashi

Re: Standard mixer control names

[Lennart Poettering]

On Mon, 23.02.09 10:11, Takashi Iwai (tiwai@suse.de) wrote:

> > ALSA is making that very hard to implement something like this because
> > every driver seems to wrap input/output selection differently.
> > 
> > On one card I have only has a couple of cswitches
> > (snd-es1371). The same one has an enum "Mic Select". Another card has
> > an enum "Input Source", but no cswitches (a HDA chip). The
> > "ControlNames.txt" file in the kernel seems to suggest that there is an
> > element "Capture Source".
> 
> That's because "Capture Source" can't work for multiple (sub)devices
> with the mixer abstraction of alsa-lib, per design.
> "Input Source" was born as a workaround (still found in many places
> in the driver code).  Maybe we should update ControlNames.txt as well.
> 
> > For playback it seems that some cards have a a headphone switch, and
> > others a headphone slider (which i guess makes sense).
> > 
> > Now, the question, how should I implement this?
> > 
> > For playback the handling is easy as long as there is only one element
> > to deal with, but what about capture? One option would be to simply
> > go by cswitch and nothing else. Or go by "Input Source" and nothing
> > else. Or combine some form. Now I'd of course prefer if the drivers
> > get fixed to use a single element naming scheme only. Is there any
> > chance to get that? And which one would that be?
> 
> I rarely believe this will be ever "fixed" in the driver side
> completely.  We may improve a bit, but not the whole stuff.
> It's no good idea to have a restriction in the driver code because
> the control API is just for generic purpose, not only about mixers.
> And, many embedded devices love to have specific unique control names
> just for their purpose...

Hmm, so this won't get fixed.

>From an application pov, how am I supposed to use the current
abstraction? What algorithm should I then pick for PulseAudio? How
should I compile the list of possible outputs and inputs? And if an
item is selected from that list, how am I supposed to activate the
entry?

For inputs: should I simply compile a list of all elements that have a
cswitch plus all items from "Mic Select" plus all items from "Input
Source"? And if an item is selected the logic would be like this: if a
cswitch is selected we simply activate it, deactivating all others. If
an item from "Mic Select" is selected we activate it in the enum and
set the cswitch for "Mic" if there is any. And if an item from "Input
Source" is seleced we activate it in the enum and set the cswitch for
"Capture" if there is any. And we ignore "Capture Source". Is that a
good idea?

For outputs: If there is a Headphone element we assume we can use the
"Master" and "Headphone" elements to switch between "Line-Out" and
"Headphone". Is that assumption correct?

Lennart

-- 
Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net         ICQ# 11060553
http://0pointer.net/lennart/           GnuPG 0x1A015CC4

Re: Standard mixer control names

[Takashi Iwai]

At Mon, 23 Feb 2009 17:47:00 +0100,
Lennart Poettering wrote:
> 
> On Mon, 23.02.09 10:11, Takashi Iwai (tiwai@suse.de) wrote:
> 
> > > ALSA is making that very hard to implement something like this because
> > > every driver seems to wrap input/output selection differently.
> > > 
> > > On one card I have only has a couple of cswitches
> > > (snd-es1371). The same one has an enum "Mic Select". Another card has
> > > an enum "Input Source", but no cswitches (a HDA chip). The
> > > "ControlNames.txt" file in the kernel seems to suggest that there is an
> > > element "Capture Source".
> > 
> > That's because "Capture Source" can't work for multiple (sub)devices
> > with the mixer abstraction of alsa-lib, per design.
> > "Input Source" was born as a workaround (still found in many places
> > in the driver code).  Maybe we should update ControlNames.txt as well.
> > 
> > > For playback it seems that some cards have a a headphone switch, and
> > > others a headphone slider (which i guess makes sense).
> > > 
> > > Now, the question, how should I implement this?
> > > 
> > > For playback the handling is easy as long as there is only one element
> > > to deal with, but what about capture? One option would be to simply
> > > go by cswitch and nothing else. Or go by "Input Source" and nothing
> > > else. Or combine some form. Now I'd of course prefer if the drivers
> > > get fixed to use a single element naming scheme only. Is there any
> > > chance to get that? And which one would that be?
> > 
> > I rarely believe this will be ever "fixed" in the driver side
> > completely.  We may improve a bit, but not the whole stuff.
> > It's no good idea to have a restriction in the driver code because
> > the control API is just for generic purpose, not only about mixers.
> > And, many embedded devices love to have specific unique control names
> > just for their purpose...
> 
> Hmm, so this won't get fixed.
> 
> From an application pov, how am I supposed to use the current
> abstraction? What algorithm should I then pick for PulseAudio? How
> should I compile the list of possible outputs and inputs? And if an
> item is selected from that list, how am I supposed to activate the
> entry?

I feel we need another meta data to manage / group the mixer elements.
It'll be likely based on the per-driver database, or implemented as a
module.  We have already a framework for mixer module, so it's
feasible.  Where it's the best choice is another question, though.

But, as now, it's still a vaporware.  So, let's assume to solve in
PA.

> For inputs: should I simply compile a list of all elements that have a
> cswitch plus all items from "Mic Select" plus all items from "Input
> Source"? And if an item is selected the logic would be like this: if a
> cswitch is selected we simply activate it, deactivating all others. If
> an item from "Mic Select" is selected we activate it in the enum and
> set the cswitch for "Mic" if there is any. And if an item from "Input
> Source" is seleced we activate it in the enum and set the cswitch for
> "Capture" if there is any. And we ignore "Capture Source". Is that a
> good idea?

In alsa-lib mixer abstraction, there is no "Capture Source" indeed.
It's always expanded to individual cswitches.  "Input Source" is never
cswitches, OTOH.  So they are basically exclusive.

The "Capture Volume" and "Capture Switch" are basically independent
from the sources.  They are a kind of "master" contorl for inputs.

Also, for inputs, there are also some exceptional mixer elements such
as "Mic Boost".  They may work both inputs & outputs, though.

> For outputs: If there is a Headphone element we assume we can use the
> "Master" and "Headphone" elements to switch between "Line-Out" and
> "Headphone". Is that assumption correct?

At least, "Headphone" control only affects the headphone output.
Ditto for "Speaker".  It's just for speaker output.

But, whether "Master" controls both HP and line-out depends on the
driver (rather codec chip).  It sucks, but because of a long history
background...


Takashi

Re: Standard mixer control names

[Pavel Hofman]

Takashi Iwai wrote:
> 
> I feel we need another meta data to manage / group the mixer elements.
> It'll be likely based on the per-driver database, or implemented as a
> module.  We have already a framework for mixer module, so it's
> feasible.  Where it's the best choice is another question, though.
> 
> But, as now, it's still a vaporware.  So, let's assume to solve in
> PA.

Great to hear about the planned progress in this area. Many cards define 
rather unintuitive but important mixer controls. Perhaps somehow we 
could provide control elements with optional textual descriptions. If it 
  was somewhere in alsa-lib configs, it would even allow for translation 
via locales. GUI mixers could display the (localized) descriptions in 
many creative ways.

Pavel.