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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