I see lots of code like this online :
http://hdlab.googlecode.com/svn/trunk/xbmc/tools/XBMCLive/setAlsaVolumes.c
Unfortunately on the raspberry Pi board the min value from
snd_mixer_selem_get_playback_volume_range() is -10239.
If I do a calculation volume*max/100 then the lowest value I can get is
zero. As a result the code only moves the volume by the top 20% ish of
its range.
Is the min value supposed to be negative or is the most common code
everyone is using broken ?
Thanks,
Jon
Example output
min=-10239 max=400 writing 0
**** Code i've crudely hacked together from various examples.
// volume is percentage
#include <alsa/asoundlib.h>
void set_volume(long volume)
{
long min, max, newvol;
snd_mixer_t *handle = NULL;
snd_mixer_selem_id_t *sid = NULL;
const char *card = "default";
//const char *selem_name = "Master";
const char *selem_name = "PCM";
if (snd_mixer_open(&handle, 0) < 0)
{
printf("%s: set_volume() RPI - snd_mixer_open
failed\n",PROGNAME);
fflush(stdout);
perror("snd_mixer_open");
}
else
{
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_malloc(&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);
if (elem == NULL)
{
printf("%s: set_volume() RPI - snd_mixer_find_selem
failed()\n",PROGNAME);
fflush(stdout);
}
else
{
snd_mixer_selem_get_playback_volume_range(elem, &min,
&max);
newvol= ( (long)volume * (long)max ) / (long)100 ;
printf("min=%ld max=%ld writing
%ld\n",min,max,newvol); fflush(stdout);
if (
snd_mixer_selem_set_playback_volume_all(elem,newvol) <0)
{
printf("%s: set_volume() RPI -
snd_mixer_selem_set_playback_volume_all() failed\n",PROGNAME);
fflush(stdout);
}
}
snd_mixer_close(handle);
}
}
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