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mixer/alsa: work around rounding error at volume 0 

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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2
NEWS
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@ -1,6 +1,8 @@
ver 0.20.17 (not yet released) ver 0.20.17 (not yet released)
* output * output
- alsa: fix crash bug with 8 channels - alsa: fix crash bug with 8 channels
* mixer
- alsa: fix rounding error at volume 0
* fix real-time and idle scheduling with Musl * fix real-time and idle scheduling with Musl
* Android * Android
- fix compatibility with Android 4.0 - fix compatibility with Android 4.0

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); 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)) { if (use_linear_dB_scale(min, max)) {
value = lrint_dir(volume * (max - min), dir) + min; value = lrint_dir(volume * (max - min), dir) + min;
return set_dB[ctl_dir](elem, value, dir); return set_dB[ctl_dir](elem, value, dir);