From 845ee1b96f76a9a322992152f1a2e9930ff396e9 Mon Sep 17 00:00:00 2001
From: Clownacy <Clownacy@users.noreply.github.com>
Date: Tue, 25 Aug 2020 02:44:54 +0100
Subject: [PATCH] Don't store subsample offset as long
Only a short is needed.
---
src/Backends/Audio/SoftwareMixer.cpp | 18 +++++++++---------
1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/src/Backends/Audio/SoftwareMixer.cpp b/src/Backends/Audio/SoftwareMixer.cpp
index 7a993eb8..896dab6a 100644
--- a/src/Backends/Audio/SoftwareMixer.cpp
+++ b/src/Backends/Audio/SoftwareMixer.cpp
@@ -15,8 +15,8 @@ struct Mixer_Sound
signed char *samples;
size_t frames;
size_t position;
- unsigned long sample_offset_remainder; // 16.16 fixed-point
- unsigned long advance_delta; // 16.16 fixed-point
+ unsigned short position_subsample;
+ unsigned long advance_delta; // 16.16 fixed-point
bool playing;
bool looping;
short volume; // 8.8 fixed-point
@@ -65,7 +65,7 @@ Mixer_Sound* Mixer_CreateSound(unsigned int frequency, const unsigned char *samp
sound->frames = length;
sound->playing = false;
sound->position = 0;
- sound->sample_offset_remainder = 0;
+ sound->position_subsample = 0;
Mixer_SetSoundFrequency(sound, frequency);
Mixer_SetSoundVolume(sound, 0);
@@ -107,7 +107,7 @@ void Mixer_StopSound(Mixer_Sound *sound)
void Mixer_RewindSound(Mixer_Sound *sound)
{
sound->position = 0;
- sound->sample_offset_remainder = 0;
+ sound->position_subsample = 0;
}
void Mixer_SetSoundFrequency(Mixer_Sound *sound, unsigned int frequency)
@@ -144,7 +144,7 @@ ATTRIBUTE_HOT void Mixer_MixSounds(long *stream, size_t frames_total)
for (size_t frames_done = 0; frames_done < frames_total; ++frames_done)
{
// Perform linear interpolation
- const unsigned char subsample = sound->sample_offset_remainder >> 8;
+ const unsigned char subsample = sound->position_subsample >> 8;
const short interpolated_sample = sound->samples[sound->position] * (0x100 - subsample)
+ sound->samples[sound->position + 1] * subsample;
@@ -154,9 +154,9 @@ ATTRIBUTE_HOT void Mixer_MixSounds(long *stream, size_t frames_total)
*stream_pointer++ += (interpolated_sample * sound->volume_r) >> 8;
// Increment sample
- sound->sample_offset_remainder += sound->advance_delta;
- sound->position += sound->sample_offset_remainder >> 16;
- sound->sample_offset_remainder &= 0xFFFF;
+ const unsigned long next_position_subsample = sound->position_subsample + sound->advance_delta;
+ sound->position += next_position_subsample >> 16;
+ sound->position_subsample = next_position_subsample & 0xFFFF;
// Stop or loop sample once it's reached its end
if (sound->position >= sound->frames)
@@ -169,7 +169,7 @@ ATTRIBUTE_HOT void Mixer_MixSounds(long *stream, size_t frames_total)
{
sound->playing = false;
sound->position = 0;
- sound->sample_offset_remainder = 0;
+ sound->position_subsample = 0;
break;
}
}