alsa-lib functions reporting conflicting information with two sound cards

alsa-lib functions reporting conflicting information with two sound cards

[nick smethurst]

Hey guys

I am rather confused that I am getting crossed information when
calling snd_names_list
and snd_pcm_info in order to gather information about pcm devices.

I have two sound cards in my development pc: RME Digi 96/8 PCI and an
onboard VIA 8237.

I'm trying to develop a piece of code that generates a list of objects
containing pcm device information, including information on virtual
devices.

My current idea is to use snd_names_list() to get a full list of
devices, and then get information about them by opening each device
and querying.

The bizzare thing is that snd_names_list() is returning comments that
do not agree with the associated device.

For example, given the following code:

#include <alsa/asoundlib.h>
int main()
{
    snd_devname_t * list;
    snd_config_update();

    snd_names_list("pcm", &list);
    while (list) {
        if (!strcmp(list->name, "hw:0,0")) {
            printf("hw:0,0 comment: %s\n", list->comment);
            break;
        }
        list = list->next;
    }
    snd_names_list_free(list);

    snd_pcm_t * pcm;
    snd_pcm_info_t * pcm_info;
    snd_pcm_info_malloc(&pcm_info);
    snd_pcm_open(&pcm, "hw:0,0", SND_PCM_STREAM_PLAYBACK, 0);
    snd_pcm_info(pcm, pcm_info);
    printf("id: %s\n", snd_pcm_info_get_id(pcm_info));
    snd_pcm_close(pcm);
    snd_pcm_info_free(pcm_info);

    return 0;
}

The result on my pc is:
    hw:0,0 comment: Physical Device - VIA 8237 (Duplex)
    id: Digi96 IEC958

So I'm apparently doing something very wrong here.

I would like to ask if there is an easier and more reliable way of
getting a list of pcm devices and querying them, and if not, what I am
doing wrong here?

Regards

Nicholas

Re: alsa-lib functions reporting conflicting information with two sound cards

[Lee Revell]

On 4/19/07, nick smethurst <nick.smethurst@gmail.com> wrote:
> Hey guys
>
> I am rather confused that I am getting crossed information when
> calling snd_names_list
> and snd_pcm_info in order to gather information about pcm devices.
>
> I have two sound cards in my development pc: RME Digi 96/8 PCI and an
> onboard VIA 8237.
>
> I'm trying to develop a piece of code that generates a list of objects
> containing pcm device information, including information on virtual
> devices.

I think ALSA's new device enumeration API can do this for you.  See
the implementation of aplay -l (or -L, don't remember which) in the
latest alsa-utils.

Lee

Re: alsa-lib functions reporting conflicting information with two sound cards

[Nicholas Smethurst]

Lee Revell wrote:
> On 4/19/07, nick smethurst <nick.smethurst@gmail.com> wrote:
>> I am rather confused that I am getting crossed information when
>> calling snd_names_list
>> and snd_pcm_info in order to gather information about pcm devices.
>
> I think ALSA's new device enumeration API can do this for you.  See
> the implementation of aplay -l (or -L, don't remember which) in the
> latest alsa-utils.
Ok, thanks for the hint (no pun intended :) ).

I see that the pcm_list() function has changed in aplay. The new hints 
API looks good.

However, I note that snd_device_name_hint() does not return hw, plughw, 
plug, dmix, etc. Are these obtained elsewhere? I would like to build a 
complete list of all available devices in order to allow the user to 
select them from a dropdown list in a GUI.

Nicholas

Re: alsa-lib functions reporting conflicting information with two sound cards

[Lee Revell]

On 4/19/07, Nicholas Smethurst <smethurst@gmail.com> wrote:
> Lee Revell wrote:
> > On 4/19/07, nick smethurst <nick.smethurst@gmail.com> wrote:
> >> I am rather confused that I am getting crossed information when
> >> calling snd_names_list
> >> and snd_pcm_info in order to gather information about pcm devices.
> >
> > I think ALSA's new device enumeration API can do this for you.  See
> > the implementation of aplay -l (or -L, don't remember which) in the
> > latest alsa-utils.
> Ok, thanks for the hint (no pun intended :) ).
>
> I see that the pcm_list() function has changed in aplay. The new hints
> API looks good.
>
> However, I note that snd_device_name_hint() does not return hw, plughw,
> plug, dmix, etc. Are these obtained elsewhere? I would like to build a
> complete list of all available devices in order to allow the user to
> select them from a dropdown list in a GUI.

Not sure, I don't have access to a machine with a modern ALSA now but
the new aplay list function definitely lists those.  I do know that
yours is exactly the problem it was designed to solve.

Lee

Getting a full device list (was: alsa-lib functions reporting conflicting information with two sound cards)

[Nicholas Smethurst]

Takashi wrote:
> At Thu, 19 Apr 2007 20:08:21 +0200,
> Nicholas Smethurst wrote:
>> However, I note that snd_device_name_hint() does not return hw, plughw,
>> plug, dmix, etc. Are these obtained elsewhere? I would like to build a
>> complete list of all available devices in order to allow the user to
>> select them from a dropdown list in a GUI.
>
> They are not shown unless you give the device description explicitly
> or set a global flag.  See the description of snd_device_name_hint()
> function.

Well I tried to understand how to do the two things you mention, but am
still stuck..

In namehint.c, I note that the snd_device_name_hint() function has the
following code:

    if (strcmp(iface, "card") == 0)
        list.iface = SND_CTL_ELEM_IFACE_CARD;
    else if (strcmp(iface, "pcm") == 0)
        list.iface = SND_CTL_ELEM_IFACE_PCM;
    else if (strcmp(iface, "rawmidi") == 0)
        list.iface = SND_CTL_ELEM_IFACE_RAWMIDI;
    else if (strcmp(iface, "timer") == 0)
        list.iface = SND_CTL_ELEM_IFACE_TIMER;
    else if (strcmp(iface, "seq") == 0)
        list.iface = SND_CTL_ELEM_IFACE_SEQUENCER;
    else if (strcmp(iface, "hwdep") == 0)
        list.iface = SND_CTL_ELEM_IFACE_HWDEP;
    else
        return -EINVAL;

which thus gives possible interface strings of "card", "pcm", "rawmidi",
"timer", "seq", and "hwdep". I concluded from this that the only way to
get the default devices is to set the global variable.

I thus tried doing the following in a small test app:

    snd_config_t * conf;
    int show_all;
    snd_config_update();
    if (snd_config_search(snd_config, "defaults.namehint.showall",
&conf) >= 0) {
        show_all = snd_config_get_bool(conf);
        if (show_all < 1) {
            snd_config_set_integer(conf, 1);
        }
    } else { // Create node.
        ...
    }

but this doesn't work.. I am apparently doing something wrong since the
global configuration is not changed with my code.

Is it possible to change global variables from a user application? Or is
it currently necessary to manually edit the alsa.conf file (as root) in
order to modify "defaults.namehint.showall" to allow applications to see
all devices?

I wish to obtain a full list of available devices in a user application
without running as root and without insisting that the user manually
edits configuration files that he doesn't understand.

Is this possible? If not, can we work towards implementing such
functionality?

Nicholas

Re: Getting a full device list (was: alsa-lib functions reporting conflicting information with two sound cards)

[Jaroslav Kysela]

On Fri, 11 May 2007, Nicholas Smethurst wrote:

> Is this possible? If not, can we work towards implementing such
> functionality?

User or system software manager should create a configuration which is 
suitable for users. You're trying to overload the user settings. Why?
Use information returned without any hacks in your application (you may 
eventually describe in documentation, how users can get more devices).

						Jaroslav

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

Re: Getting a full device list

[Nicholas Smethurst]

Jaroslav Kysela wrote:
> On Fri, 11 May 2007, Nicholas Smethurst wrote:
> 
>> Is this possible? If not, can we work towards implementing such
>> functionality?
> 
> User or system software manager should create a configuration which is 
> suitable for users. You're trying to overload the user settings. Why?
> Use information returned without any hacks in your application (you may 
> eventually describe in documentation, how users can get more devices).

I'm not sure I understand.

I found the global variable "defaults.namehint.showall" in alsa.conf, which
lives in /usr/share/alsa/. This is not the sort of place a user should be
fiddling with. Users don't have the knowledge (or the desire) to manually
change system configuration files.. us developers should be able to do all we
need to do via alsa-lib.

I understand that you are suggesting that user applications list what ever
snd_device_name_hint() returns, and then describe in the application
documentation that if the user does not see devices such as hw, they should
manually edit a system configuration file.

Or do you mean that a user application can create its own global
configuration? I didn't know that that was possible.

If this is the case, can I copy the default configuration and turn on
"defaults.namehint.showall" in order that my user application can call have
the full list from snd_device_name_hint()?

Nicholas

Re: Getting a full device list

[Jaroslav Kysela]

On Fri, 11 May 2007, Nicholas Smethurst wrote:

> Jaroslav Kysela wrote:
> > On Fri, 11 May 2007, Nicholas Smethurst wrote:
> > 
> >> Is this possible? If not, can we work towards implementing such
> >> functionality?
> > 
> > User or system software manager should create a configuration which is 
> > suitable for users. You're trying to overload the user settings. Why?
> > Use information returned without any hacks in your application (you may 
> > eventually describe in documentation, how users can get more devices).
> 
> I'm not sure I understand.
> 
> I found the global variable "defaults.namehint.showall" in alsa.conf, which
> lives in /usr/share/alsa/. This is not the sort of place a user should be
> fiddling with. Users don't have the knowledge (or the desire) to manually
> change system configuration files.. us developers should be able to do all we
> need to do via alsa-lib.

Note that's why many distributions exist and make configuration more 
user friendly. We decided to have minimal set of offered devices by 
default. If any distribution feels it's better to give a full list, it's 
also possible by modifying the global configuration file.

> I understand that you are suggesting that user applications list what ever
> snd_device_name_hint() returns, and then describe in the application
> documentation that if the user does not see devices such as hw, they should
> manually edit a system configuration file.

Yes (but files in share tree should not be touched - you may override 
config via system configuration in /etc/asound.conf or user 
specific ~/.asoundrc).

> Or do you mean that a user application can create its own global
> configuration? I didn't know that that was possible.
> 
> If this is the case, can I copy the default configuration and turn on
> "defaults.namehint.showall" in order that my user application can call have
> the full list from snd_device_name_hint()?

Again, why this hack? Why your application should behave differently than 
others?

Anyway, you may specify a path to own alsa.conf file via ALSA_CONFIG_PATH 
environment variable. But if you feel in this way, it's far better to 
modify user's ~/.asoundrc file in my eyes (don't forget to tell user that 
you are doing something with the configuration, or ask user at first).

						Jaroslav

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

Re: Getting a full device list

[Takashi Iwai]

At Fri, 11 May 2007 13:05:36 +0200,
Nicholas Smethurst wrote:
> 
> Jaroslav Kysela wrote:
> > On Fri, 11 May 2007, Nicholas Smethurst wrote:
> > 
> >> Is this possible? If not, can we work towards implementing such
> >> functionality?
> > 
> > User or system software manager should create a configuration which is 
> > suitable for users. You're trying to overload the user settings. Why?
> > Use information returned without any hacks in your application (you may 
> > eventually describe in documentation, how users can get more devices).
> 
> I'm not sure I understand.
> 
> I found the global variable "defaults.namehint.showall" in alsa.conf, which
> lives in /usr/share/alsa/. This is not the sort of place a user should be
> fiddling with. Users don't have the knowledge (or the desire) to manually
> change system configuration files.. us developers should be able to do all we
> need to do via alsa-lib.

You can override the values easily in user configuration, e.g. by
adding the following line to ~/.asoundrc:

	defaults.namehist.showall	on

To force to override even the variable type, you can add '!' modifier,

	defaults.namehist.!showall	1


Takashi

Re: Getting a full device list

[Nicholas Smethurst]

Takashi Iwai wrote:
> You can override the values easily in user configuration, e.g. by
> adding the following line to ~/.asoundrc:
> 
> 	defaults.namehist.showall	on
> 
> To force to override even the variable type, you can add '!' modifier,
> 
> 	defaults.namehist.!showall	1

So global variables found in alsa.conf can be overridden in ~/.asoundrc.. I
didn't realise this either..

Thanks for the advice.

Nicholas

Re: Getting a full device list

[Nicholas Smethurst]

Takashi Iwai wrote:
> You can override the values easily in user configuration, e.g. by
> adding the following line to ~/.asoundrc:
> 
> 	defaults.namehist.showall	on
> 
> To force to override even the variable type, you can add '!' modifier,
> 
> 	defaults.namehist.!showall	1
> 

Well I tried doing both of the above in ~/.asoundrc, but I'm still not getting
any listing of the pcm hw or plughw devices, or any plugins.

The only thing that changes is the addition the following when calling the
hints function with "hwdep":

    hw:CARD=PAD
       RME Digi96/8 PAD

    hw:CARD=UART
       MPU-401 UART

    hw:CARD=V8237
       VIA 8237

I'm not sure what hwdep means exactly.. Are these also pcm devices?

Here's my test application.. Is there anything wrong here?

#include <alsa/asoundlib.h>
#include <iostream>

int main()
{
    size_t start, end;
    std::string desc;
    void ** hints, ** str_c;
    char * name_c, * desc_c;
    int index = 0;
    const char * ifaces[] = {
        "card", "pcm", "rawmidi", "timer", "seq", "hwdep", 0
    };

    snd_config_update();

    while (ifaces[index]) {
        std::cout << "---- Trying \"" << ifaces[index] << "\" ----\n\n";
        if (snd_device_name_hint(-1, ifaces[index], &hints) < 0) {
            std::cerr << "hint failed on \"" << ifaces[index] << "\"\n\n";
            ++index;
            continue;
        }

        str_c = hints;
        while (*str_c) {
            name_c = snd_device_name_get_hint(*str_c, "NAME");
            desc_c = snd_device_name_get_hint(*str_c, "DESC");

            std::cout << name_c << "\n";
            start = 0;
            desc = desc_c;
            do {
                end = desc.find("\n", start);
                std::cout << "   " << desc.substr(start, end - start) << "\n";
                start = end + 1;
            } while (end != std::string::npos);
            std::cout << "\n";
            free(name_c);
            free(desc_c);
            ++str_c;
        }
        snd_device_name_free_hint(hints);
        ++index;
    }
    return 0;
}


My system has two soundcards: an RME Digi96/8 PAD and an onboard VIA. The RME
has two devices, and the VIA four.

The result of the test application with showall set to on is the following:

---- Trying "card" ----

hint failed on "card"

---- Trying "pcm" ----

default:CARD=PAD
   RME Digi96/8 PAD, Digi96 IEC958
   Default Audio Device

null
   Discard all samples (playback) or generate zero samples (capture)

default:CARD=UART
   MPU-401 UART
   Default Audio Device

default:CARD=V8237
   VIA 8237, VIA 8237
   Default Audio Device

front:CARD=V8237,DEV=0
   VIA 8237, VIA 8237
   Front speakers

surround40:CARD=V8237,DEV=0
   VIA 8237, VIA 8237
   4.0 Surround output to Front and Rear speakers

surround41:CARD=V8237,DEV=0
   VIA 8237, VIA 8237
   4.1 Surround output to Front, Rear and Subwoofer speakers

surround50:CARD=V8237,DEV=0
   VIA 8237, VIA 8237
   5.0 Surround output to Front, Center and Rear speakers

surround51:CARD=V8237,DEV=0
   VIA 8237, VIA 8237
   5.1 Surround output to Front, Center, Rear and Subwoofer speakers

iec958:CARD=V8237,DEV=0
   VIA 8237, VIA 8237
   IEC958 (S/PDIF) Digital Audio Output

---- Trying "rawmidi" ----

hw:CARD=PAD
   RME Digi96/8 PAD
   Direct rawmidi driver device

hw:CARD=UART,DEV=0
   MPU-401 UART, MPU-401 UART MIDI
   Direct rawmidi driver device

hw:CARD=V8237
   VIA 8237
   Direct rawmidi driver device

---- Trying "timer" ----

---- Trying "seq" ----

---- Trying "hwdep" ----

hw:CARD=PAD
   RME Digi96/8 PAD

hw:CARD=UART
   MPU-401 UART

hw:CARD=V8237
   VIA 8237

Re: Getting a full device list

[Takashi Iwai]

At Mon, 14 May 2007 10:36:48 +0200,
Nicholas Smethurst wrote:
> 
> Takashi Iwai wrote:
> > You can override the values easily in user configuration, e.g. by
> > adding the following line to ~/.asoundrc:
> > 
> > 	defaults.namehist.showall	on
> > 
> > To force to override even the variable type, you can add '!' modifier,
> > 
> > 	defaults.namehist.!showall	1
> > 
> 
> Well I tried doing both of the above in ~/.asoundrc, but I'm still not getting
> any listing of the pcm hw or plughw devices, or any plugins.

A typo of "namehint", sorry.


Takashi

Re: Getting a full device list

[Nicholas Smethurst]

Takashi Iwai wrote:
> At Mon, 14 May 2007 10:36:48 +0200,
> Nicholas Smethurst wrote:
>> Takashi Iwai wrote:
>>> You can override the values easily in user configuration, e.g. by
>>> adding the following line to ~/.asoundrc:
>>>
>>> 	defaults.namehist.showall	on
>>>
>>> To force to override even the variable type, you can add '!' modifier,
>>>
>>> 	defaults.namehist.!showall	1
>>>
>> Well I tried doing both of the above in ~/.asoundrc, but I'm still not getting
>> any listing of the pcm hw or plughw devices, or any plugins.
> 
> A typo of "namehint", sorry.
> 
> 
> Takashi
> 

I did see the typo before, and I corrected it before testing.. I had used:

	defaults.namehint.showall on
and
	defaults.namehint.!showall 1

for my tests - my results are in the previous email.

Re: Getting a full device list

[Takashi Iwai]

At Mon, 14 May 2007 11:27:38 +0200,
Nicholas Smethurst wrote:
> 
> Takashi Iwai wrote:
> > At Mon, 14 May 2007 10:36:48 +0200,
> > Nicholas Smethurst wrote:
> >> Takashi Iwai wrote:
> >>> You can override the values easily in user configuration, e.g. by
> >>> adding the following line to ~/.asoundrc:
> >>>
> >>> 	defaults.namehist.showall	on
> >>>
> >>> To force to override even the variable type, you can add '!' modifier,
> >>>
> >>> 	defaults.namehist.!showall	1
> >>>
> >> Well I tried doing both of the above in ~/.asoundrc, but I'm still not getting
> >> any listing of the pcm hw or plughw devices, or any plugins.
> > 
> > A typo of "namehint", sorry.
> > 
> > 
> > Takashi
> > 
> 
> I did see the typo before, and I corrected it before testing.. I had used:
> 
> 	defaults.namehint.showall on
> and
> 	defaults.namehint.!showall 1
> 
> for my tests - my results are in the previous email.

Hm, do you see any change in "aplay -L" output with and without this
definition?


Takashi

Re: Getting a full device list

[Nicholas Smethurst]

Takashi Iwai wrote:
>> 	defaults.namehint.showall on
>> and
>> 	defaults.namehint.!showall 1
>>
>> for my tests - my results are in the previous email.
> 
> Hm, do you see any change in "aplay -L" output with and without this
> definition?

No, "aplay -L" gives the same list with or without the option. I tried
changing it in /usr/share/alsa/alsa.conf as well, but the change had no effect.

NB: this is with 1.0.14rc4.


nicholas@Nicholas:~$ aplay -L
default:CARD=V8237
    VIA 8237, VIA 8237
    Default Audio Device
front:CARD=V8237,DEV=0
    VIA 8237, VIA 8237
    Front speakers
surround40:CARD=V8237,DEV=0
    VIA 8237, VIA 8237
    4.0 Surround output to Front and Rear speakers
surround41:CARD=V8237,DEV=0
    VIA 8237, VIA 8237
    4.1 Surround output to Front, Rear and Subwoofer speakers
surround50:CARD=V8237,DEV=0
    VIA 8237, VIA 8237
    5.0 Surround output to Front, Center and Rear speakers
surround51:CARD=V8237,DEV=0
    VIA 8237, VIA 8237
    5.1 Surround output to Front, Center, Rear and Subwoofer speakers
iec958:CARD=V8237,DEV=0
    VIA 8237, VIA 8237
    IEC958 (S/PDIF) Digital Audio Output
null
    Discard all samples (playback) or generate zero samples (capture)
default:CARD=UART
    MPU-401 UART
    Default Audio Device
default:CARD=PAD
    RME Digi96/8 PAD, Digi96 IEC958
    Default Audio Device

nicholas@Nicholas:~$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: V8237 [VIA 8237], device 0: VIA 8237 [VIA 8237]
  Subdevices: 4/4
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
card 0: V8237 [VIA 8237], device 1: VIA 8237 [VIA 8237]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 2: PAD [RME Digi96/8 PAD], device 0: Digi96 IEC958 [Digi96 IEC958]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 2: PAD [RME Digi96/8 PAD], device 1: Digi96 ADAT [Digi96 ADAT]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

Re: Getting a full device list

[Takashi Iwai]

At Mon, 14 May 2007 12:38:49 +0200,
Nicholas Smethurst wrote:
> 
> Takashi Iwai wrote:
> >> 	defaults.namehint.showall on
> >> and
> >> 	defaults.namehint.!showall 1
> >>
> >> for my tests - my results are in the previous email.
> > 
> > Hm, do you see any change in "aplay -L" output with and without this
> > definition?
> 
> No, "aplay -L" gives the same list with or without the option. I tried
> changing it in /usr/share/alsa/alsa.conf as well, but the change had no effect.

Then something wrong with your set up.  It works for me.  aplay -L
shows different outputs with the "showal on".

You should check whether ~/.asoundrc is really read.


Takashi

Re: alsa-lib functions reporting conflicting information with two sound cards

[Takashi Iwai]

At Thu, 19 Apr 2007 20:08:21 +0200,
Nicholas Smethurst wrote:
> 
> Lee Revell wrote:
> > On 4/19/07, nick smethurst <nick.smethurst@gmail.com> wrote:
> >> I am rather confused that I am getting crossed information when
> >> calling snd_names_list
> >> and snd_pcm_info in order to gather information about pcm devices.
> >
> > I think ALSA's new device enumeration API can do this for you.  See
> > the implementation of aplay -l (or -L, don't remember which) in the
> > latest alsa-utils.
> Ok, thanks for the hint (no pun intended :) ).
> 
> I see that the pcm_list() function has changed in aplay. The new hints 
> API looks good.
> 
> However, I note that snd_device_name_hint() does not return hw, plughw, 
> plug, dmix, etc. Are these obtained elsewhere? I would like to build a 
> complete list of all available devices in order to allow the user to 
> select them from a dropdown list in a GUI.

They are not shown unless you give the device description explicitly
or set a global flag.  See the description of snd_device_name_hint()
function.


Takashi