Problem solved, thanks Takashi!

Archiving for benefit of future generations, here's what made it work for me:

void SetAlsaMasterVolume(long volume){ long min, max; snd_mixer_t *handle; snd_mixer_selem_id_t *sid; const char *card = "hw2"; // just for this example, don't hard-code this! const char *selem_name = "PCM"; // for some reason Master didn't work, but PCM does...

snd_mixer_open(&handle, 0); snd_mixer_attach(handle, card); snd_mixer_selem_register(handle, NULL, NULL); snd_mixer_load(handle);

snd_mixer_selem_id_alloca(&sid); snd_mixer_selem_id_set_index(sid, 0); // no need to change the index in this case snd_mixer_selem_id_set_name(sid, selem_name); snd_mixer_elem_t* elem = snd_mixer_find_selem(handle, sid);

snd_mixer_selem_get_playback_volume_range(elem, &min, &max); snd_mixer_selem_set_playback_volume_all(elem, volume * max / 100);

snd_mixer_close(handle); }

2015-04-30 11:53 GMT+02:00 Takashi Iwai tiwai@suse.de:

At Thu, 30 Apr 2015 10:29:14 +0200, Bram Bos wrote:

...

Ok, so perhaps this is not the forum to ask support for using ALSA in application development.

It's no wrong place, but not everybody has enough time, so be patient :)

...

Can anyone point me to a place where I can ask such questions.?

The existing ALSA documentation is not sufficient to help me out here.

The device name concept isn't written so much, although it's a quite basic idea. Maybe someone should work on it.

As you have already noticed, ALSA device may contain the card number. For the control / mixer API, you can get the direct access to a certain hardware with "hw:X" name string where X is the card number.

Takashi

...

Thanks!

2015-04-29 16:15 GMT+02:00 Bram Bos buramu@gmail.com:

...

I want to get access to the ALSA Simple Mixer interface, but rather

than

...

...

the 'default' sound device I want to target a specific USB sound

device.

...

...

I'm at a loss how to refer to it... I am using a modified version of

the

...

...

code below but I have no idea what to replace the "card" and

"selem_name"

...

...

strings with. The device name? The 'hwX.Y' string?

And do I need to change the index#?

Too many variables to solve this by trial and error. Any hints appreciated!

void SetAlsaMasterVolume(long volume){ long min, max; snd_mixer_t *handle; snd_mixer_selem_id_t *sid; const char *card = "default"; const char *selem_name = "Master";

snd_mixer_open(&handle, 0);
snd_mixer_attach(handle, card);
snd_mixer_selem_register(handle, NULL, NULL);
snd_mixer_load(handle);

snd_mixer_selem_id_alloca(&sid);
snd_mixer_selem_id_set_index(sid, 0);
snd_mixer_selem_id_set_name(sid, selem_name);
snd_mixer_elem_t* elem = snd_mixer_find_selem(handle, sid);

snd_mixer_selem_get_playback_volume_range(elem, &min, &max);
snd_mixer_selem_set_playback_volume_all(elem, volume * max / 100);

snd_mixer_close(handle);}

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