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Don't store subsample offset as long

Only a short is needed.

--- a/src/Backends/Audio/SoftwareMixer.cpp

+++ b/src/Backends/Audio/SoftwareMixer.cpp

@@ -15,8 +15,8 @@

 	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 @@

 	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_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 @@

 			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 @@

 				*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 @@

 					{

 						sound->playing = false;

 						sound->position = 0;

-						sound->sample_offset_remainder = 0;

+						sound->position_subsample = 0;

 						break;

 					}

 				}