On Mon, 2013-04-15 at 21:20 +0200, Clemens Ladisch wrote:
> jon wrote:
> > Is the min value supposed to be negative or is the most common code
> > everyone is using broken ?
>
> > snd_mixer_selem_get_playback_volume_range(elem, &min, &max);
> > newvol= ( (long)volume * (long)max ) / (long)100 ;
> > if ( snd_mixer_selem_set_playback_volume_all(elem,newvol) <0)
>
> Ignoring the min value is, of course, wrong.
>
> "Math is hard, let's go shopping!"
> File a bug and suggest to go shopping here:
> <http://git.alsa-project.org/?p=alsa-utils.git;a=blob;f=alsamixer/volume_mapping.c;hb=HEAD>
>
>
Thanks :-)
I had already hacked round the issue, not good at math though - it
shows.
Looks like the code you pointed at would offer a more progressive volume
than this:
// **************************************************** Raspberry Pi
#ifdef RPI
#ifdef ALSA
#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";
float vpercent, fnewvol;
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);
vpercent = (float)volume/100;
fnewvol = (float)min + vpercent * ( (float)max -
(float)min);
newvol = (long)fnewvol;
//printf("volume=%ld min=%ld max=%ld
newvol=%ld\n",volume,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);
}
}
#endif // ALSA
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