diff options
| author | Benjamin Valentin <benpicco@googlemail.com> | 2020-12-28 19:45:08 +0100 |
|---|---|---|
| committer | Tanu Kaskinen <tanuk@iki.fi> | 2021-01-18 17:36:12 +0200 |
| commit | 10ac01a2066b3d0a58ecc3e3db98dd43c284a209 (patch) | |
| tree | 77da1980c704a32335c6ddf5a1c0a8bea7836c02 /src/modules/alsa/alsa-mixer.c | |
| parent | 4868fcf5f344af613172f61d9105c02f3f07e1ab (diff) | |
alsa-mixer: disable has_dB if max_dB is negative
Volume scaling in dB mode is broken if max dB is negative.
I have a Nobsound USB amplifier (1908:2220) that reports a dB range
of -127.07 dB to -128 dB in Alsa.
While this is likely a driver/device bug, in my naive imagination
userspace wouldn't bother too much with the absolute values and just set
out_dB(percent) = min_dB + (max_dB - min_dB) * percent
However, this is not what PulseAudio is doing, instead max_dB is used
as base_volume with which the desired software volume is multiplied
while min_dB does not seem to be taken into account.
The result is that with this device only a tiny portion of the volume
slider is usable.
Setting it to 97% already reaches min_dB which effectively turns any
(software) audio knob to an on/off switch.
To work around this, simply set the has_dB flag to false if max_dB is
negative.
This falls back to using raw Alsa values (ranging from 0 - 255), now
the settings in pavucontrol perfectly mirror those in alsamixer.
Part-of: <https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/447>
Diffstat (limited to 'src/modules/alsa/alsa-mixer.c')
| -rw-r--r-- | src/modules/alsa/alsa-mixer.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/src/modules/alsa/alsa-mixer.c b/src/modules/alsa/alsa-mixer.c index a6e6672ad..1cfc42633 100644 --- a/src/modules/alsa/alsa-mixer.c +++ b/src/modules/alsa/alsa-mixer.c @@ -1711,6 +1711,14 @@ static bool element_probe_volume(pa_alsa_element *e, snd_mixer_elem_t *me) { else e->has_dB = snd_mixer_selem_get_capture_dB_range(me, &min_dB, &max_dB) >= 0; + /* Assume decibel data to be incorrect if max_dB is negative. */ + if (e->has_dB && max_dB < 0) { + pa_alsa_mixer_id_to_string(buf, sizeof(buf), &e->alsa_id); + pa_log_warn("The decibel volume range for element %s (%li dB - %li dB) has negative maximum. " + "Disabling the decibel range.", buf, min_dB, max_dB); + e->has_dB = false; + } + /* Check that the kernel driver returns consistent limits with * both _get_*_dB_range() and _ask_*_vol_dB(). */ if (e->has_dB && !e->db_fix) { |