/* $Id$ */ /** @file mixer.cpp Mixing of sound samples. */ #include "stdafx.h" #include "mixer.h" #include "core/math_func.hpp" struct MixerChannel { bool active; /* pointer to allocated buffer memory */ int8 *memory; /* current position in memory */ uint32 pos; uint32 frac_pos; uint32 frac_speed; uint32 samples_left; /* Mixing volume */ int volume_left; int volume_right; bool is16bit; }; static MixerChannel _channels[8]; static uint32 _play_rate = 11025; /** * The theoretical maximum volume for a single sound sample. Multiple sound * samples should not exceed this limit as it will sound too loud. It also * stops overflowing when too many sounds are played at the same time, which * causes an even worse sound quality. */ static const int MAX_VOLUME = 128 * 128; /** * Perform the rate conversion between the input and output. * @param b the buffer to read the data from * @param frac_pos the position from the begin of the buffer till the next element * @tparam T the size of the buffer (8 or 16 bits) * @return the converted value. */ template <typename T> static int RateConversion(T *b, int frac_pos) { return ((b[0] * ((1 << 16) - frac_pos)) + (b[1] * frac_pos)) >> 16; } static void mix_int16(MixerChannel *sc, int16 *buffer, uint samples) { int16 *b; uint32 frac_pos; uint32 frac_speed; int volume_left; int volume_right; if (samples > sc->samples_left) samples = sc->samples_left; sc->samples_left -= samples; assert(samples > 0); b = (int16*)sc->memory + sc->pos; frac_pos = sc->frac_pos; frac_speed = sc->frac_speed; volume_left = sc->volume_left; volume_right = sc->volume_right; if (frac_speed == 0x10000) { /* Special case when frac_speed is 0x10000 */ do { buffer[0] = Clamp(buffer[0] + (*b * volume_left >> 16), -MAX_VOLUME, MAX_VOLUME); buffer[1] = Clamp(buffer[1] + (*b * volume_right >> 16), -MAX_VOLUME, MAX_VOLUME); b++; buffer += 2; } while (--samples > 0); } else { do { int data = RateConversion(b, frac_pos); buffer[0] = Clamp(buffer[0] + (data * volume_left >> 16), -MAX_VOLUME, MAX_VOLUME); buffer[1] = Clamp(buffer[1] + (data * volume_right >> 16), -MAX_VOLUME, MAX_VOLUME); buffer += 2; frac_pos += frac_speed; b += frac_pos >> 16; frac_pos &= 0xffff; } while (--samples > 0); } sc->frac_pos = frac_pos; sc->pos = b - (int16*)sc->memory; } static void mix_int8_to_int16(MixerChannel *sc, int16 *buffer, uint samples) { int8 *b; uint32 frac_pos; uint32 frac_speed; int volume_left; int volume_right; if (samples > sc->samples_left) samples = sc->samples_left; sc->samples_left -= samples; assert(samples > 0); b = sc->memory + sc->pos; frac_pos = sc->frac_pos; frac_speed = sc->frac_speed; volume_left = sc->volume_left; volume_right = sc->volume_right; if (frac_speed == 0x10000) { /* Special case when frac_speed is 0x10000 */ do { buffer[0] = Clamp(buffer[0] + (*b * volume_left >> 8), -MAX_VOLUME, MAX_VOLUME); buffer[1] = Clamp(buffer[1] + (*b * volume_right >> 8), -MAX_VOLUME, MAX_VOLUME); b++; buffer += 2; } while (--samples > 0); } else { do { int data = RateConversion(b, frac_pos); buffer[0] = Clamp(buffer[0] + (data * volume_left >> 8), -MAX_VOLUME, MAX_VOLUME); buffer[1] = Clamp(buffer[1] + (data * volume_right >> 8), -MAX_VOLUME, MAX_VOLUME); buffer += 2; frac_pos += frac_speed; b += frac_pos >> 16; frac_pos &= 0xffff; } while (--samples > 0); } sc->frac_pos = frac_pos; sc->pos = b - sc->memory; } static void MxCloseChannel(MixerChannel *mc) { free(mc->memory); mc->active = false; mc->memory = NULL; } void MxMixSamples(void *buffer, uint samples) { MixerChannel *mc; /* Clear the buffer */ memset(buffer, 0, sizeof(int16) * 2 * samples); /* Mix each channel */ for (mc = _channels; mc != endof(_channels); mc++) { if (mc->active) { if (mc->is16bit) { mix_int16(mc, (int16*)buffer, samples); } else { mix_int8_to_int16(mc, (int16*)buffer, samples); } if (mc->samples_left == 0) MxCloseChannel(mc); } } } MixerChannel *MxAllocateChannel() { MixerChannel *mc; for (mc = _channels; mc != endof(_channels); mc++) if (mc->memory == NULL) { mc->active = false; return mc; } return NULL; } void MxSetChannelRawSrc(MixerChannel *mc, int8 *mem, size_t size, uint rate, bool is16bit) { mc->memory = mem; mc->frac_pos = 0; mc->pos = 0; mc->frac_speed = (rate << 16) / _play_rate; /* adjust the magnitude to prevent overflow */ while (size & ~0xFFFF) { size >>= 1; rate = (rate >> 1) + 1; } int div = is16bit ? 2 : 1; mc->samples_left = (uint)size * _play_rate / rate / div; mc->is16bit = is16bit; } void MxSetChannelVolume(MixerChannel *mc, uint left, uint right) { mc->volume_left = left; mc->volume_right = right; } void MxActivateChannel(MixerChannel *mc) { mc->active = true; } bool MxInitialize(uint rate) { _play_rate = rate; return true; }