101 lines
2.7 KiB
C
101 lines
2.7 KiB
C
/* Based on raylib audio_stream_effects example */
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#include <lua.h>
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#include <lauxlib.h>
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#include <lualib.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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/* gcc audioProcess.c -shared -o audioProcess.so -fPIC -llua */
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// Audio effect: lowpass filter
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void AudioProcessEffectLPF(void *buffer, unsigned int frames)
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{
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static float low[2] = { 0.0f, 0.0f };
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static const float cutoff = 70.0f / 44100.0f; // 70 Hz lowpass filter
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const float k = cutoff / (cutoff + 0.1591549431f); // RC filter formula
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// Converts the buffer data before using it
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float *bufferData = (float *)buffer;
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for (unsigned int i = 0; i < frames*2; i += 2)
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{
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const float l = bufferData[i];
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const float r = bufferData[i + 1];
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low[0] += k * (l - low[0]);
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low[1] += k * (r - low[1]);
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bufferData[i] = low[0];
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bufferData[i + 1] = low[1];
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}
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}
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static float *delayBuffer = NULL;
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static unsigned int delayBufferSize = 0;
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static unsigned int delayReadIndex = 2;
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static unsigned int delayWriteIndex = 0;
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// Audio effect: delay
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static void AudioProcessEffectDelay(void *buffer, unsigned int frames)
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{
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for (unsigned int i = 0; i < frames*2; i += 2)
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{
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float leftDelay = delayBuffer[delayReadIndex++]; // ERROR: Reading buffer -> WHY??? Maybe thread related???
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float rightDelay = delayBuffer[delayReadIndex++];
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if (delayReadIndex == delayBufferSize) delayReadIndex = 0;
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((float *)buffer)[i] = 0.5f*((float *)buffer)[i] + 0.5f*leftDelay;
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((float *)buffer)[i + 1] = 0.5f*((float *)buffer)[i + 1] + 0.5f*rightDelay;
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delayBuffer[delayWriteIndex++] = ((float *)buffer)[i];
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delayBuffer[delayWriteIndex++] = ((float *)buffer)[i + 1];
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if (delayWriteIndex == delayBufferSize) delayWriteIndex = 0;
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}
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}
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/* API. */
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static int apInit( lua_State* L ) {
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// Allocate buffer for the delay effect
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delayBufferSize = 48000*2; // 1 second delay (device sampleRate*channels)
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delayBuffer = (float *)calloc(delayBufferSize, sizeof(float));
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return 0;
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}
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static int getAudioProcessEffectLPF( lua_State* L ) {
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lua_pushlightuserdata( L, AudioProcessEffectLPF );
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return 1;
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}
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static int getAudioProcessEffectDelay( lua_State* L ) {
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lua_pushlightuserdata( L, AudioProcessEffectDelay );
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return 1;
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}
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static int apFree( lua_State* L ) {
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free(delayBuffer); // Free delay buffer
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return 0;
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}
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static const luaL_Reg audioProcess[] = {
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{ "init", apInit },
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{ "AudioProcessEffectLPF", getAudioProcessEffectLPF },
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{ "AudioProcessEffectDelay", getAudioProcessEffectDelay },
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{ "free", apFree },
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{ NULL, NULL } // sentinel.
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};
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int luaopen_audioProcess(lua_State *L) {
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#if LUA_VERSION_NUM <= 501
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luaL_openlib( L, "audioProcess", audioProcess, 0 );
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#else
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luaL_newlib( L, audioProcess );
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#endif
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return 1;
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}
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