180 lines
4.5 KiB
C++
180 lines
4.5 KiB
C++
#include "SoftwareMixer.h"
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#include <math.h>
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#include <stddef.h>
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#include <stdlib.h>
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#include "../../Attributes.h"
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#define MIN(a, b) ((a) < (b) ? (a) : (b))
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#define MAX(a, b) ((a) > (b) ? (a) : (b))
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#define CLAMP(x, y, z) MIN(MAX((x), (y)), (z))
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struct Mixer_Sound
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{
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signed char *samples;
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size_t frames;
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size_t position;
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unsigned long sample_offset_remainder; // 16.16 fixed-point
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unsigned long advance_delta; // 16.16 fixed-point
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bool playing;
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bool looping;
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short volume; // 8.8 fixed-point
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short pan_l; // 8.8 fixed-point
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short pan_r; // 8.8 fixed-point
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short volume_l; // 8.8 fixed-point
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short volume_r; // 8.8 fixed-point
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struct Mixer_Sound *next;
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};
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static Mixer_Sound *sound_list_head;
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static unsigned long output_frequency;
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static unsigned short MillibelToScale(long volume)
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{
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// Volume is in hundredths of a decibel, from 0 to -10000
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volume = CLAMP(volume, -10000, 0);
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return (unsigned short)(pow(10.0, volume / 2000.0) * 256.0f);
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}
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void Mixer_Init(unsigned long frequency)
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{
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output_frequency = frequency;
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}
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Mixer_Sound* Mixer_CreateSound(unsigned int frequency, const unsigned char *samples, size_t length)
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{
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Mixer_Sound *sound = (Mixer_Sound*)malloc(sizeof(Mixer_Sound));
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if (sound == NULL)
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return NULL;
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sound->samples = (signed char*)malloc(length + 1);
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if (sound->samples == NULL)
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{
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free(sound);
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return NULL;
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}
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for (size_t i = 0; i < length; ++i)
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sound->samples[i] = samples[i] - 0x80; // Convert from unsigned 8-bit PCM to signed
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sound->frames = length;
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sound->playing = false;
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sound->position = 0;
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sound->sample_offset_remainder = 0;
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Mixer_SetSoundFrequency(sound, frequency);
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Mixer_SetSoundVolume(sound, 0);
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Mixer_SetSoundPan(sound, 0);
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sound->next = sound_list_head;
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sound_list_head = sound;
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return sound;
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}
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void Mixer_DestroySound(Mixer_Sound *sound)
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{
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for (Mixer_Sound **sound_pointer = &sound_list_head; *sound_pointer != NULL; sound_pointer = &(*sound_pointer)->next)
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{
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if (*sound_pointer == sound)
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{
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*sound_pointer = sound->next;
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free(sound->samples);
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free(sound);
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break;
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}
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}
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}
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void Mixer_PlaySound(Mixer_Sound *sound, bool looping)
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{
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sound->playing = true;
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sound->looping = looping;
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sound->samples[sound->frames] = looping ? sound->samples[0] : 0; // For the linear interpolator
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}
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void Mixer_StopSound(Mixer_Sound *sound)
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{
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sound->playing = false;
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}
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void Mixer_RewindSound(Mixer_Sound *sound)
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{
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sound->position = 0;
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sound->sample_offset_remainder = 0;
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}
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void Mixer_SetSoundFrequency(Mixer_Sound *sound, unsigned int frequency)
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{
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sound->advance_delta = (frequency << 16) / output_frequency;
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}
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void Mixer_SetSoundVolume(Mixer_Sound *sound, long volume)
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{
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sound->volume = MillibelToScale(volume);
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sound->volume_l = (sound->pan_l * sound->volume) >> 8;
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sound->volume_r = (sound->pan_r * sound->volume) >> 8;
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}
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void Mixer_SetSoundPan(Mixer_Sound *sound, long pan)
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{
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sound->pan_l = MillibelToScale(-pan);
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sound->pan_r = MillibelToScale(pan);
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sound->volume_l = (sound->pan_l * sound->volume) >> 8;
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sound->volume_r = (sound->pan_r * sound->volume) >> 8;
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}
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// Most CPU-intensive function in the game (2/3rd CPU time consumption in my experience), so marked with ATTRIBUTE_HOT so the compiler considers it a hot spot (as it is) when optimizing
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ATTRIBUTE_HOT void Mixer_MixSounds(long *stream, size_t frames_total)
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{
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for (Mixer_Sound *sound = sound_list_head; sound != NULL; sound = sound->next)
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{
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if (sound->playing)
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{
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long *stream_pointer = stream;
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for (size_t frames_done = 0; frames_done < frames_total; ++frames_done)
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{
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// Perform linear interpolation
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const unsigned char subsample = sound->sample_offset_remainder >> 8;
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const short interpolated_sample = sound->samples[sound->position] * (0x100 - subsample)
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+ sound->samples[sound->position + 1] * subsample;
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// Mix, and apply volume
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*stream_pointer++ += (interpolated_sample * sound->volume_l) >> 8;
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*stream_pointer++ += (interpolated_sample * sound->volume_r) >> 8;
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// Increment sample
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sound->sample_offset_remainder += sound->advance_delta;
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sound->position += sound->sample_offset_remainder >> 16;
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sound->sample_offset_remainder &= 0xFFFF;
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// Stop or loop sample once it's reached its end
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if (sound->position >= sound->frames)
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{
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if (sound->looping)
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{
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sound->position %= sound->frames;
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}
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else
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{
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sound->playing = false;
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sound->position = 0;
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sound->sample_offset_remainder = 0;
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break;
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}
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}
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}
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}
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}
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}
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