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mixer/alsa: work around rounding error at volume 0

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Due to rounding errors, a slightly negative value can be passed to
set_normalized_volume(), which will make the log10() call fail.
Actually, volume 0 is already failing because log10(0) is illegal.  So
let's fix this by implementing two corner cases: <=0 and >=100.

Closes #212
This commit is contained in:
Max Kellermann
2018-02-10 09:07:51 +01:00
parent e0ca4b865a
commit bede564618
2 changed files with 9 additions and 0 deletions
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7
src/mixer/plugins/volume_mapping.c
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@@ -139,6 +139,13 @@ static int set_normalized_volume(snd_mixer_elem_t *elem,
return set_raw[ctl_dir](elem, value);
}
/* two special cases to avoid rounding errors at 0% and
100% */
if (volume <= 0)
return set_dB[ctl_dir](elem, min, dir);
else if (volume >= 100)
return set_dB[ctl_dir](elem, max, dir);
if (use_linear_dB_scale(min, max)) {
value = lrint_dir(volume * (max - min), dir) + min;
return set_dB[ctl_dir](elem, value, dir);