ref: 479fff2ccf6ac2f28f91d5d558e5a8c20ed811a4
parent: 7334440c2757df39bf1293e036ac44bb779ef0e5
author: Clownacy <Clownacy@users.noreply.github.com>
date: Tue Jun 23 20:49:11 EDT 2020
New mostly-integer-only sound mixer The mixer itself is integer-only, but the millibel stuff is still float-based (I don't know if it's worth adding a 10001-value-long lookup table to replace it). Anyway, according to a quick test, this new mixer is significantly faster than the old floating-point one - rarely going above 100 clock() ticks per callback, with the old one almost always running above that. For now, only the SDL2 backend supports it - I'll add the others in upcoming commits. This will no-doubt cause problems with the enhanced (lite) branch, where clownaudio always outputs float samples.
--- a/src/Backends/Audio/SDL2.cpp
+++ b/src/Backends/Audio/SDL2.cpp
@@ -23,11 +23,10 @@
{(void)user_data;
- float *stream = (float*)stream_uint8;
- unsigned int frames_total = len / sizeof(float) / 2;
+ short *stream = (short*)stream_uint8;
+ unsigned int frames_total = len / sizeof(short) / 2;
- for (unsigned int i = 0; i < frames_total * 2; ++i)
- stream[i] = 0.0f;
+ memset(stream, 0, len);
if (organya_callback_milliseconds == 0)
{@@ -60,6 +59,17 @@
organya_countdown -= frames_to_do;
}
}
+
+ // Clamp output, and convert from 8-bit to 16-bit
+ for (unsigned int i = 0; i < frames_total * 2; ++i)
+ {+ if (stream[i] > 0x7F)
+ stream[i] = 0x7F00;
+ else if (stream[i] < -0x7F)
+ stream[i] = -0x7F00;
+ else
+ stream[i] <<= 8;
+ }
}
bool AudioBackend_Init(void)
@@ -78,7 +88,7 @@
SDL_AudioSpec specification;
specification.freq = 48000;
- specification.format = AUDIO_F32;
+ specification.format = AUDIO_S16;
specification.channels = 2;
specification.samples = 0x400; // Roughly 10 milliseconds for 48000Hz
specification.callback = Callback;
--- a/src/Backends/Audio/SoftwareMixer.cpp
+++ b/src/Backends/Audio/SoftwareMixer.cpp
@@ -16,16 +16,16 @@
{signed char *samples;
size_t frames;
- double position;
- double advance_delta;
+ size_t position;
+ unsigned long sample_offset_remainder; // 16.16 fixed-point
+ unsigned long advance_delta;
bool playing;
bool looping;
- unsigned int frequency;
- float volume;
- float pan_l;
- float pan_r;
- float volume_l;
- float volume_r;
+ short volume;
+ short pan_l;
+ short pan_r;
+ short volume_l;
+ short volume_r;
struct Mixer_Sound *next;
};
@@ -34,11 +34,11 @@
static unsigned long output_frequency;
-static double MillibelToScale(long volume)
+static unsigned short MillibelToScale(long volume)
{// Volume is in hundredths of a decibel, from 0 to -10000
volume = CLAMP(volume, -10000, 0);
- return pow(10.0, volume / 2000.0);
+ return (unsigned short)(pow(10.0, volume / 2000.0) * 256.0f);
}
void Mixer_Init(unsigned long frequency)
@@ -66,7 +66,8 @@
sound->frames = length;
sound->playing = false;
- sound->position = 0.0;
+ sound->position = 0;
+ sound->sample_offset_remainder = 0;
Mixer_SetSoundFrequency(sound, frequency);
Mixer_SetSoundVolume(sound, 0);
@@ -107,68 +108,70 @@
void Mixer_RewindSound(Mixer_Sound *sound)
{- sound->position = 0.0;
+ sound->position = 0;
+ sound->sample_offset_remainder = 0;
}
void Mixer_SetSoundFrequency(Mixer_Sound *sound, unsigned int frequency)
{- sound->frequency = frequency;
- sound->advance_delta = (double)frequency / (double)output_frequency;
+ sound->advance_delta = (frequency << 16) / output_frequency;
}
void Mixer_SetSoundVolume(Mixer_Sound *sound, long volume)
{- sound->volume = (float)MillibelToScale(volume);
+ sound->volume = MillibelToScale(volume);
- sound->volume_l = sound->pan_l * sound->volume;
- sound->volume_r = sound->pan_r * sound->volume;
+ sound->volume_l = (sound->pan_l * sound->volume) >> 8;
+ sound->volume_r = (sound->pan_r * sound->volume) >> 8;
}
void Mixer_SetSoundPan(Mixer_Sound *sound, long pan)
{- sound->pan_l = (float)MillibelToScale(-pan);
- sound->pan_r = (float)MillibelToScale(pan);
+ sound->pan_l = MillibelToScale(-pan);
+ sound->pan_r = MillibelToScale(pan);
- sound->volume_l = sound->pan_l * sound->volume;
- sound->volume_r = sound->pan_r * sound->volume;
+ sound->volume_l = (sound->pan_l * sound->volume) >> 8;
+ sound->volume_r = (sound->pan_r * sound->volume) >> 8;
}
-// Most CPU-intensive function in the game (2/3rd CPU time consumption in my experience), so marked with attrHot so the compiler considers it a hot spot (as it is) when optimizing
-ATTRIBUTE_HOT void Mixer_MixSounds(float *stream, unsigned int frames_total)
+// 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
+ATTRIBUTE_HOT void Mixer_MixSounds(short *stream, unsigned int frames_total)
{for (Mixer_Sound *sound = sound_list_head; sound != NULL; sound = sound->next)
{if (sound->playing)
{- float *stream_pointer = stream;
+ short *stream_pointer = stream;
for (unsigned int frames_done = 0; frames_done < frames_total; ++frames_done)
{- const size_t position_integral = (size_t)sound->position;
- const float position_fractional = sound->position - position_integral;
-
- // Get two samples, and normalise them to 0-1
- const float sample1 = sound->samples[position_integral] / 128.0f;
- const float sample2 = sound->samples[position_integral + 1] / 128.0f;
-
// Perform linear interpolation
- const float interpolated_sample = sample1 + (sample2 - sample1) * position_fractional;
+ const unsigned char subsample = sound->sample_offset_remainder >> 8;
- *stream_pointer++ += interpolated_sample * sound->volume_l;
- *stream_pointer++ += interpolated_sample * sound->volume_r;
+ const signed char interpolated_sample = ((sound->samples[sound->position] * (0x100 - subsample)) >> 8)
+ + ((sound->samples[sound->position + 1] * subsample) >> 8);
- sound->position += sound->advance_delta;
+ // Mix, and apply volume
+ *stream_pointer++ += (interpolated_sample * sound->volume_l) >> 8;
+ *stream_pointer++ += (interpolated_sample * sound->volume_r) >> 8;
+ // Incrememt sample
+ sound->sample_offset_remainder += sound->advance_delta;
+ sound->position += sound->sample_offset_remainder >> 16;
+ sound->sample_offset_remainder &= 0xFFFF;
+
+ // Stop or loop sample once it's reached its end
if (sound->position >= sound->frames)
{if (sound->looping)
{- sound->position = fmod(sound->position, (double)sound->frames);
+ sound->position %= sound->frames;
}
else
{sound->playing = false;
- sound->position = 0.0;
+ sound->position = 0;
+ sound->sample_offset_remainder = 0;
break;
}
}
--- a/src/Backends/Audio/SoftwareMixer.h
+++ b/src/Backends/Audio/SoftwareMixer.h
@@ -13,4 +13,4 @@
void Mixer_SetSoundFrequency(Mixer_Sound *sound, unsigned int frequency);
void Mixer_SetSoundVolume(Mixer_Sound *sound, long volume);
void Mixer_SetSoundPan(Mixer_Sound *sound, long pan);
-void Mixer_MixSounds(float *stream, unsigned int frames_total);
+void Mixer_MixSounds(short *stream, unsigned int frames_total);