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Different optimisation for software-mixer

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`trunc` can resolve to a library call, while a cast-to-int doesn't
appear to. Since the mixer already does a cast-to-int when retrieving
samples, I can kill two birds with one stone.
This commit is contained in:
Clownacy 2020-04-06 13:40:39 +01:00
parent 1016411fa4
commit 545948584a
1 changed files with 7 additions and 4 deletions
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11
src/Backends/Audio/SoftwareMixer.cpp
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@ -1,6 +1,6 @@
#include "SoftwareMixer.h"
#include <cmath>
#include <math.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
@ -150,12 +150,15 @@ ATTRIBUTE_HOT void Mixer_MixSounds(float *stream, unsigned int frames_total)
for (unsigned int frames_done = 0; frames_done < frames_total; ++frames_done)
{
const size_t position_integral = (size_t)sound->position;
const double position_fractional = sound->position - position_integral;
// Get two samples, and normalise them to 0-1
const float sample1 = (sound->samples[(size_t)sound->position] - 128.0f) / 128.0f;
const float sample2 = (sound->samples[(size_t)sound->position + 1] - 128.0f) / 128.0f;
const float sample1 = (sound->samples[position_integral] - 128.0f) / 128.0f;
const float sample2 = (sound->samples[position_integral + 1] - 128.0f) / 128.0f;
// Perform linear interpolation
const float interpolated_sample = sample1 + (sample2 - sample1) * (sound->position - std::trunc(sound->position));
const float interpolated_sample = sample1 + (sample2 - sample1) * position_fractional;
*steam_pointer++ += interpolated_sample * sound->volume_l;
*steam_pointer++ += interpolated_sample * sound->volume_r;