hw/audio/hda-codec.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
According Intel's High Definition Audio Specification (Revision 1.0a,
Section 7.3.4.10: Amplifier Capabilities), the amplifier gain levels
should be evenly spaced in dB, i.e. using a log scale instead of linear.
Here, the hda-codec reports amplifier levels from 0 to -48 dB at 1-dB
steps matching the 8-bit dynamic range, and the -49 dB level is mapped
to 0 (muted).
Signed-off-by: Yuanqing Li <liyq.yuanqing@outlook.com>
---
hw/audio/hda-codec.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/hw/audio/hda-codec.c b/hw/audio/hda-codec.c
index c51d8ba617..c2aa71624b 100644
--- a/hw/audio/hda-codec.c
+++ b/hw/audio/hda-codec.c
@@ -121,7 +121,7 @@ static void hda_codec_parse_fmt(uint32_t format, struct audsettings *as)
#define QEMU_HDA_PCM_FORMATS (AC_SUPPCM_BITS_16 | \
0x1fc /* 16 -> 96 kHz */)
#define QEMU_HDA_AMP_NONE (0)
-#define QEMU_HDA_AMP_STEPS 0x4a
+#define QEMU_HDA_AMP_STEPS 0x31 /* 20 * log10(255) = 48 dB dynamic range */
#define PARAM mixemu
#define HDA_MIXER
@@ -433,6 +433,14 @@ static void hda_audio_set_running(HDAAudioStream *st, bool running)
}
}
+/* first muted; then from -48 dB to 0 dB */
+static const uint32_t hda_vol_table[] = {
+ 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 4, 4, 5,
+ 5, 6, 6, 7, 8, 9, 10, 11, 13, 14, 16, 18, 20, 23, 26,
+ 29, 32, 36, 40, 45, 51, 57, 64, 72, 81, 90, 102, 114, 128, 143,
+ 161, 181, 203, 227, 255
+}
+
static void hda_audio_set_amp(HDAAudioStream *st)
{
bool muted;
@@ -446,8 +454,8 @@ static void hda_audio_set_amp(HDAAudioStream *st)
left = st->mute_left ? 0 : st->gain_left;
right = st->mute_right ? 0 : st->gain_right;
- left = left * 255 / QEMU_HDA_AMP_STEPS;
- right = right * 255 / QEMU_HDA_AMP_STEPS;
+ left = hda_vol_table[left];
+ right = hda_vol_table[right];
if (!st->state->mixer) {
return;
--
2.41.0
Hi On Sun, Jul 30, 2023 at 5:52 PM Yuanqing Li <liyq.yuanqing@outlook.com> wrote: > > According Intel's High Definition Audio Specification (Revision 1.0a, > Section 7.3.4.10: Amplifier Capabilities), the amplifier gain levels > should be evenly spaced in dB, i.e. using a log scale instead of linear. > > Here, the hda-codec reports amplifier levels from 0 to -48 dB at 1-dB > steps matching the 8-bit dynamic range, and the -49 dB level is mapped > to 0 (muted). > > Signed-off-by: Yuanqing Li <liyq.yuanqing@outlook.com> > --- > hw/audio/hda-codec.c | 14 +++++++++++--- > 1 file changed, 11 insertions(+), 3 deletions(-) > > diff --git a/hw/audio/hda-codec.c b/hw/audio/hda-codec.c > index c51d8ba617..c2aa71624b 100644 > --- a/hw/audio/hda-codec.c > +++ b/hw/audio/hda-codec.c > @@ -121,7 +121,7 @@ static void hda_codec_parse_fmt(uint32_t format, struct audsettings *as) > #define QEMU_HDA_PCM_FORMATS (AC_SUPPCM_BITS_16 | \ > 0x1fc /* 16 -> 96 kHz */) > #define QEMU_HDA_AMP_NONE (0) > -#define QEMU_HDA_AMP_STEPS 0x4a > +#define QEMU_HDA_AMP_STEPS 0x31 /* 20 * log10(255) = 48 dB dynamic range */ > > #define PARAM mixemu > #define HDA_MIXER > @@ -433,6 +433,14 @@ static void hda_audio_set_running(HDAAudioStream *st, bool running) > } > } > > +/* first muted; then from -48 dB to 0 dB */ > +static const uint32_t hda_vol_table[] = { > + 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 4, 4, 5, > + 5, 6, 6, 7, 8, 9, 10, 11, 13, 14, 16, 18, 20, 23, 26, > + 29, 32, 36, 40, 45, 51, 57, 64, 72, 81, 90, 102, 114, 128, 143, > + 161, 181, 203, 227, 255 > +} It was not clear to me which scale is applied by the backend. I guess mixeng uses linear, and thus all others should too. > + > static void hda_audio_set_amp(HDAAudioStream *st) > { > bool muted; > @@ -446,8 +454,8 @@ static void hda_audio_set_amp(HDAAudioStream *st) > left = st->mute_left ? 0 : st->gain_left; > right = st->mute_right ? 0 : st->gain_right; > > - left = left * 255 / QEMU_HDA_AMP_STEPS; > - right = right * 255 / QEMU_HDA_AMP_STEPS; > + left = hda_vol_table[left]; > + right = hda_vol_table[right]; > Whoo, better check bounds here. (value can go up to AC_AMP_GAIN 0x7f, reading the code) Definitely not trivial material imho -- Marc-André Lureau
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