diff options
| author | Oswald Buddenhagen <oswald.buddenhagen@gmx.de> | 2023-05-14 19:03:22 +0200 |
|---|---|---|
| committer | Takashi Iwai <tiwai@suse.de> | 2023-05-15 22:06:21 +0200 |
| commit | 1298bc978afba0a507cedd0a91e53267ca152804 (patch) | |
| tree | c296aac53cf5a76dd91ed58cfc6fc6bd899a47f7 /include/sound/emu10k1.h | |
| parent | de0dc31070a54d146bb5e7e5a739c9588034165c (diff) | |
ALSA: emu10k1: enable bit-exact playback, part 1: DSP attenuation
Fractional multiplication with the maximal value 2^31-1 causes some tiny
distortion. Instead, we want to multiply with the full 2^31. The catch
is of course that this cannot be represented in the DSP's signed 32 bit
registers.
One way to deal with this is to encode 1.0 as a negative number and
special-case it. As a matter of fact, the SbLive! code path already
contained such code, though the controls never actually exercised it.
A more efficient approach is to use negative values, which actually
extend to -2^31. Accordingly, for all the volume adjustments we now use
the MAC1 instruction which negates the X operand.
The range of the controls in highres mode is extended downwards, so -1
is the new zero/mute. At maximal excursion, real zero is not mute any
more, but I don't think anyone will notice this behavior change. ;-)
That also required making the min/max/values in the control structs
signed. This technically changes the user space interface, but it seems
implausible that someone would notice - the numbers were actually
treated as if they were signed anyway (and in the actual mixer iface
they _are_). And without this change, the min value didn't even make
sense in the first place (and no-one noticed, because it was always 0).
Tested-by: Jonathan Dowland <jon@dow.land>
Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Link: https://lore.kernel.org/r/20230514170323.3408834-7-oswald.buddenhagen@gmx.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'include/sound/emu10k1.h')
| -rw-r--r-- | include/sound/emu10k1.h | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/include/sound/emu10k1.h b/include/sound/emu10k1.h index e9b1729ade60..8e27f7074230 100644 --- a/include/sound/emu10k1.h +++ b/include/sound/emu10k1.h @@ -1508,9 +1508,9 @@ struct snd_emu10k1_fx8010_ctl { unsigned int vcount; unsigned int count; /* count of GPR (1..16) */ unsigned short gpr[32]; /* GPR number(s) */ - unsigned int value[32]; - unsigned int min; /* minimum range */ - unsigned int max; /* maximum range */ + int value[32]; + int min; /* minimum range */ + int max; /* maximum range */ unsigned int translation; /* translation type (EMU10K1_GPR_TRANSLATION*) */ struct snd_kcontrol *kcontrol; }; |