snd_mixer_selem_ask_playback_vol_dB calculates wrong volume with SND_CTL_TLVT_DB_MINMAX_MUTE

snd_mixer_selem_ask_playback_vol_dB calculates wrong volume with SND_CTL_TLVT_DB_MINMAX_MUTE

[GitHub issues - opened]

alsa-project/alsa-lib issue #504 was opened from pv:

snd_mixer_selem_ask_playback_dB_vol() and snd_mixer_selem_ask_playback_vol_dB() are inconsistent between each other when SND_CTL_TLVT_DB_MINMAX_MUTE  is enabled. Similarly for `snd_mixer_selem_get_playback_dB` after setting volume dB_vol returned.

Version: alsa-lib-1.2.15.3-3.fc44.x86_64

In Pipewire, we have
```
if ((r = snd_mixer_selem_ask_playback_dB_vol(me, value_dB, rounding, &val)) < 0)
    return r;
if ((r = snd_mixer_selem_ask_playback_vol_dB(me, val, &dB)) < 0)
    return r;
```
In the problem case `value_dB = -3259` and `rounding = +1` but I'm seeing
```
(gdb) p	val
$55 = 1
(gdb) p	dB
$56 = -9999999
```
The `val = 1` is correct (the device is muted only at HW volume 0), but dB from snd_mixer_selem_ask_playback_vol_dB is wrong. (Results to Pipewire volume control being broken at low volume.)

The device in question is "1532:055e Razer USA, Ltd Razer Nommo V2 X" -- it is muted at lowest ALSA hw volume 0, and anything > 0 is not muted (so it needs the mixer_playback_min_mute quirk).

In snd_tlv_convert_to_dB:
```
snd_tlv_convert_to_dB (tlv=0x7b460cd21610, rangemin=0, rangemax=7248, volume=1, db_gain=0x7b260b455e40) at control/tlv.c:212
254                     if (*db_gain < mindb)
(gdb) p	type
$80 = 5
(gdb) p	mindb
$72 = -2837
(gdb) p	maxdb
$73 = -6
```
The `*db_gain = (maxdb - mindb) * (volume - rangemin) / (rangemax - rangemin) + mindb`  results to `*db_gain == mindb` and the function returns with SND_CTL_TLV_DB_GAIN_MUTE which is wrong.

Reverging https://github.com/alsa-project/alsa-lib/commit/41039b49ad3e20506134864028c77aeaba4c0d51 appears to fix it for me (get `dB ==  -2837`).

I don't understand the new logic, doesn't SND_CTL_TLVT_DB_MINMAX_MUTE mean that the lowest hardware volume value is muted? (Also, the ALSA 1/100 dB values round to zero earlier than the USB 1/256 dB ones.)

Link: https://gitlab.freedesktop.org/pipewire/pipewire/-/work_items/5235 (I also have access to similar device locally)

Issue URL     : https://github.com/alsa-project/alsa-lib/issues/504
Repository URL: https://github.com/alsa-project/alsa-lib

snd_mixer_selem_ask_playback_vol_dB calculates wrong volume with SND_CTL_TLVT_DB_MINMAX_MUTE

[GitHub issues - edited]

alsa-project/alsa-lib issue #504 was edited from pv:

snd_mixer_selem_ask_playback_dB_vol() and snd_mixer_selem_ask_playback_vol_dB() are inconsistent between each other when SND_CTL_TLVT_DB_MINMAX_MUTE  is enabled. Similarly for `snd_mixer_selem_get_playback_dB` after setting volume dB_vol returned.

Version: alsa-lib-1.2.15.3-3.fc44.x86_64

In Pipewire, we have
```
if ((r = snd_mixer_selem_ask_playback_dB_vol(me, value_dB, rounding, &val)) < 0)
    return r;
if ((r = snd_mixer_selem_ask_playback_vol_dB(me, val, &dB)) < 0)
    return r;
```
In the problem case `value_dB = -3259` and `rounding = +1` but I'm seeing
```
(gdb) p	val
$55 = 1
(gdb) p	dB
$56 = -9999999
```
The `val = 1` is correct (the device is muted only at HW volume 0), but dB from snd_mixer_selem_ask_playback_vol_dB is wrong. (Results to Pipewire volume control being broken at low volume.)

The device in question is "1532:055e Razer USA, Ltd Razer Nommo V2 X" -- it is muted at lowest ALSA hw volume 0, and anything > 0 is not muted (so it needs the mixer_playback_min_mute quirk).

In snd_tlv_convert_to_dB:
```
snd_tlv_convert_to_dB (tlv=0x7b460cd21610, rangemin=0, rangemax=7248, volume=1, db_gain=0x7b260b455e40) at control/tlv.c:212
254                     if (*db_gain < mindb)
(gdb) p	type
$80 = 5
(gdb) p	mindb
$72 = -2837
(gdb) p	maxdb
$73 = -6
```
The `*db_gain = (maxdb - mindb) * (volume - rangemin) / (rangemax - rangemin) + mindb`  results to `*db_gain == mindb` and the function returns with SND_CTL_TLV_DB_GAIN_MUTE which is wrong.

Reverting https://github.com/alsa-project/alsa-lib/commit/41039b49ad3e20506134864028c77aeaba4c0d51 appears to fix it for me (get `dB ==  -2837`).  Alternatively one could change snd_tlv_convert_from_dB to match so the rounding is right.

I don't understand the new logic, doesn't SND_CTL_TLVT_DB_MINMAX_MUTE mean that the lowest hardware volume value is muted? (Also, the ALSA 1/100 dB values round to zero earlier than the USB 1/256 dB ones.)

Link: https://gitlab.freedesktop.org/pipewire/pipewire/-/work_items/5235 (I also have access to similar device locally)

Issue URL     : https://github.com/alsa-project/alsa-lib/issues/504
Repository URL: https://github.com/alsa-project/alsa-lib

snd_mixer_selem_ask_playback_vol_dB calculates wrong volume with SND_CTL_TLVT_DB_MINMAX_MUTE

[GitHub issues - edited]

alsa-project/alsa-lib issue #504 was edited from pv:

snd_mixer_selem_ask_playback_dB_vol() and snd_mixer_selem_ask_playback_vol_dB() are inconsistent between each other when SND_CTL_TLVT_DB_MINMAX_MUTE  is enabled. Similarly for `snd_mixer_selem_get_playback_dB` after setting volume dB_vol returned.

Version: alsa-lib-1.2.15.3-3.fc44.x86_64

In Pipewire, we have
```
if ((r = snd_mixer_selem_ask_playback_dB_vol(me, value_dB, rounding, &val)) < 0)
    return r;
if ((r = snd_mixer_selem_ask_playback_vol_dB(me, val, &dB)) < 0)
    return r;
```
In the problem case `value_dB = -3259` and `rounding = +1` but I'm seeing
```
(gdb) p	val
$55 = 1
(gdb) p	dB
$56 = -9999999
```
The `val = 1` is correct (the device is muted only at HW volume 0), but dB from snd_mixer_selem_ask_playback_vol_dB is wrong, the device is not muted at volume 1. (The inconsistency results to Pipewire volume control being broken at low volume.)

The device in question is "1532:055e Razer USA, Ltd Razer Nommo V2 X" -- it is muted at lowest ALSA hw volume 0, and anything > 0 is not muted (so it needs the mixer_playback_min_mute quirk).

In snd_tlv_convert_to_dB:
```
snd_tlv_convert_to_dB (tlv=0x7b460cd21610, rangemin=0, rangemax=7248, volume=1, db_gain=0x7b260b455e40) at control/tlv.c:212
254                     if (*db_gain < mindb)
(gdb) p	type
$80 = 5
(gdb) p	mindb
$72 = -2837
(gdb) p	maxdb
$73 = -6
```
The `*db_gain = (maxdb - mindb) * (volume - rangemin) / (rangemax - rangemin) + mindb`  results to `*db_gain == mindb` and the function returns with SND_CTL_TLV_DB_GAIN_MUTE which is wrong.

Reverting https://github.com/alsa-project/alsa-lib/commit/41039b49ad3e20506134864028c77aeaba4c0d51 appears to fix it for me (get `dB ==  -2837`).  Alternatively one could change snd_tlv_convert_from_dB to match so the rounding is right.

I don't understand the new logic, doesn't SND_CTL_TLVT_DB_MINMAX_MUTE mean that the lowest hardware volume value is muted? (Also, the ALSA 1/100 dB values round to zero earlier than the USB 1/256 dB ones.)

Link: https://gitlab.freedesktop.org/pipewire/pipewire/-/work_items/5235 (I also have access to similar device locally)

Issue URL     : https://github.com/alsa-project/alsa-lib/issues/504
Repository URL: https://github.com/alsa-project/alsa-lib