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audio: change mixing engine float range to [-1.f, 1.f] 

Currently the internal float range of the mixing engine is
[-.5f, .5f]. PulseAudio, SDL2 and libasound use a [-1.f, 1.f]
range. This means with float samples the audio playback volume
is 6dB too low and audio recording signals will be clipped in
most cases.

To avoid another scaling factor in the conv_natural_float_* and
clip_natural_float_* functions with FLOAT_MIXENG defined this
patch changes the mixing engine float range to [-1.f, 1.f].

Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
Message-id: 20200308193321.20668-4-vr_qemu@t-online.de
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
master
Volker Rümelin 2020-03-08 20:33:19 +01:00 committed by Gerd Hoffmann
parent 33a93baeae
commit 4218fdd77f
2 changed files with 10 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
audio/mixeng.c
View File

@ -271,11 +271,11 @@ f_sample *mixeng_clip[2][2][2][3] = {
#define CONV_NATURAL_FLOAT(x) (x)
#define CLIP_NATURAL_FLOAT(x) (x)
#else
static const float float_scale = UINT_MAX;
static const float float_scale = UINT_MAX / 2.f;
#define CONV_NATURAL_FLOAT(x) ((x) * float_scale)
#ifdef RECIPROCAL
static const float float_scale_reciprocal = 1.f / UINT_MAX;
static const float float_scale_reciprocal = 2.f / UINT_MAX;
#define CLIP_NATURAL_FLOAT(x) ((x) * float_scale_reciprocal)
#else
#define CLIP_NATURAL_FLOAT(x) ((x) / float_scale)

17
audio/mixeng_template.h
View File

@ -41,32 +41,31 @@ static inline mixeng_real glue (conv_, ET) (IN_T v)
#ifdef RECIPROCAL
#ifdef SIGNED
return nv * (1.f / (mixeng_real) (IN_MAX - IN_MIN));
return nv * (2.f / ((mixeng_real)IN_MAX - IN_MIN));
#else
return (nv - HALF) * (1.f / (mixeng_real) IN_MAX);
return (nv - HALF) * (2.f / (mixeng_real)IN_MAX);
#endif
#else /* !RECIPROCAL */
#ifdef SIGNED
return nv / (mixeng_real) ((mixeng_real) IN_MAX - IN_MIN);
return nv / (((mixeng_real)IN_MAX - IN_MIN) / 2.f);
#else
return (nv - HALF) / (mixeng_real) IN_MAX;
return (nv - HALF) / ((mixeng_real)IN_MAX / 2.f);
#endif
#endif
}
static inline IN_T glue (clip_, ET) (mixeng_real v)
{
if (v >= 0.5) {
if (v >= 1.f) {
return IN_MAX;
}
else if (v < -0.5) {
} else if (v < -1.f) {
return IN_MIN;
}
#ifdef SIGNED
return ENDIAN_CONVERT ((IN_T) (v * ((mixeng_real) IN_MAX - IN_MIN)));
return ENDIAN_CONVERT((IN_T)(v * (((mixeng_real)IN_MAX - IN_MIN) / 2.f)));
#else
return ENDIAN_CONVERT ((IN_T) ((v * IN_MAX) + HALF));
return ENDIAN_CONVERT((IN_T)((v * ((mixeng_real)IN_MAX / 2.f)) + HALF));
#endif
}