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implement true zero gain for maximum attenuation (#396)

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fixes #319
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Tom M 2018-06-15 18:46:10 +02:00 committed by GitHub
parent 0921ccc4c0
commit 29d1947ccc
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GPG key ID: 4AEE18F83AFDEB23
1 changed files with 16 additions and 1 deletions
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17
src/rvoice/fluid_rvoice_mixer.c
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@ -310,6 +310,21 @@ fluid_rvoice_buffers_mix(fluid_rvoice_buffers_t* buffers,
int start_block, int sample_count,
fluid_real_t** dest_bufs, int dest_bufcount)
{
/*
* SF2.04 9.1.7 Envelope Generators:
*
* "When 96 dB of attenuation is reached in the final gain amplifier,
* an abrupt jump to zero gain (infinite dB of attenuation) occurs."
*
* fluidsynth is a 24 bit synth, it could (should??) use 144 dB of attenuation.
* However the spec makes no distinction between 16 or 24 bit synths, so use
* 96 dB here.
*
* This magic number was obtained by
* powl(10.0L, -FLUID_PEAK_ATTENUATION / 200.0L);
*/
static const fluid_real_t MIN_GAIN = 0.000015848931924611135L;
int bufcount = buffers->count;
int i, dsp_i;
if (sample_count <= 0 || dest_bufcount <= 0)
@ -322,7 +337,7 @@ fluid_rvoice_buffers_mix(fluid_rvoice_buffers_t* buffers,
fluid_real_t *FLUID_RESTRICT buf = get_dest_buf(buffers, i, dest_bufs, dest_bufcount);
fluid_real_t amp = buffers->bufs[i].amp;
if (buf == NULL || amp == 0.0f)
if (buf == NULL || amp <= MIN_GAIN)
continue;
FLUID_ASSERT((uintptr_t)buf % FLUID_DEFAULT_ALIGNMENT == 0);