diff options
| author | Oswald Buddenhagen <oswald.buddenhagen@gmx.de> | 2023-05-14 19:03:23 +0200 |
|---|---|---|
| committer | Takashi Iwai <tiwai@suse.de> | 2023-05-16 11:11:04 +0200 |
| commit | bcdbd3b7888e1db89b7b2f7c78237c9ed5c2ebb1 (patch) | |
| tree | 28e01cac493ddac6d65e345e5bf07dd20219477d /include/sound/emu10k1.h | |
| parent | 1298bc978afba0a507cedd0a91e53267ca152804 (diff) | |
ALSA: emu10k1: enable bit-exact playback, part 2: voice attenuation
The voice volume is a raw fractional multiplier that can't actually
represent 1.0. To still enable real pass-through, we now set the volume
to 0.5 (which results in no loss of precision, as the FX bus provides
fractional values) and scale up the samples in DSP code.
To maintain backwards compatibility with existing configuration files,
we rescale the values in the mixer controls. The range is extended
upwards from 0xffff to 0x1fffd, which actually introduces the
possibility of specifying an amplification.
There is still a minor incompatibility with user space, namely if
someone loaded custom DSP code. They'll just get half the volume, so
this doesn't seem like a big deal.
Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Link: https://lore.kernel.org/r/20230514170323.3408834-8-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 | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/include/sound/emu10k1.h b/include/sound/emu10k1.h index 8e27f7074230..7bcb1a2d779a 100644 --- a/include/sound/emu10k1.h +++ b/include/sound/emu10k1.h @@ -415,6 +415,7 @@ SUB_REG(PTRX, PITCHTARGET, 0xffff0000) /* Pitch target of specified channel */ SUB_REG(PTRX, FXSENDAMOUNT_A, 0x0000ff00) /* Linear level of channel output sent to FX send bus A */ SUB_REG(PTRX, FXSENDAMOUNT_B, 0x000000ff) /* Linear level of channel output sent to FX send bus B */ +// Note: the volumes are raw multpliers, so real 100% is impossible. #define CVCF 0x02 /* Current volume and filter cutoff register */ SUB_REG(CVCF, CURRENTVOL, 0xffff0000) /* Current linear volume of specified channel */ SUB_REG(CVCF, CURRENTFILTER, 0x0000ffff) /* Current filter cutoff frequency of specified channel */ @@ -1477,6 +1478,8 @@ struct snd_emu10k1_pcm_mixer { /* mono, left, right x 8 sends (4 on emu10k1) */ unsigned char send_routing[3][8]; unsigned char send_volume[3][8]; + // 0x8000 is neutral. The mixer code rescales it to 0xffff to maintain + // backwards compatibility with user space. unsigned short attn[3]; struct snd_emu10k1_pcm *epcm; }; |