mirror of https://github.com/bsnes-emu/bsnes.git
Emulate AGB audio mixing
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parent
795823e372
commit
91eeb4d9d5
76
Core/apu.c
76
Core/apu.c
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@ -23,6 +23,13 @@ static void refresh_channel(GB_gameboy_t *gb, unsigned index, unsigned cycles_of
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static bool is_DAC_enabled(GB_gameboy_t *gb, unsigned index)
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{
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if (gb->model >= GB_MODEL_AGB) {
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/* On the AGB, mixing is done digitally, so there are no per-channel
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DACs. Instead, all channels are summed digital regardless of
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whatever the DAC state would be on a CGB or earlier model. */
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return true;
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}
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switch (index) {
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case GB_SQUARE_1:
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return gb->io_registers[GB_IO_NR12] & 0xF8;
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@ -37,11 +44,45 @@ static bool is_DAC_enabled(GB_gameboy_t *gb, unsigned index)
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return gb->io_registers[GB_IO_NR42] & 0xF8;
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}
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return 0;
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return false;
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}
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static void update_sample(GB_gameboy_t *gb, unsigned index, int8_t value, unsigned cycles_offset)
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{
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if (gb->model >= GB_MODEL_AGB) {
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/* On the AGB, because no analog mixing is done, the behavior of NR51 is a bit different.
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A channel that is not connected to a terminal is idenitcal to a connected channel
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playing PCM sample 0. */
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gb->apu.samples[index] = value;
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if (gb->apu_output.sample_rate) {
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unsigned right_volume = (gb->io_registers[GB_IO_NR50] & 7) + 1;
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unsigned left_volume = ((gb->io_registers[GB_IO_NR50] >> 4) & 7) + 1;
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GB_sample_t output;
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if (gb->io_registers[GB_IO_NR51] & (1 << index)) {
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output.right = (0xf - value * 2) * right_volume;
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}
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else {
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output.right = 0xf * right_volume;
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}
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if (gb->io_registers[GB_IO_NR51] & (0x10 << index)) {
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output.left = (0xf - value * 2) * left_volume;
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}
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else {
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output.left = 0xf * left_volume;
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}
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if (*(uint32_t *)&(gb->apu_output.current_sample[index]) != *(uint32_t *)&output) {
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refresh_channel(gb, index, cycles_offset);
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gb->apu_output.current_sample[index] = output;
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}
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}
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return;
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}
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if (!is_DAC_enabled(gb, index)) {
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value = gb->apu.samples[index];
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}
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@ -73,23 +114,26 @@ static void render(GB_gameboy_t *gb, bool no_downsampling, GB_sample_t *dest)
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UNROLL
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for (unsigned i = 0; i < GB_N_CHANNELS; i++) {
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double multiplier = CH_STEP;
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if (!is_DAC_enabled(gb, i)) {
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gb->apu_output.dac_discharge[i] -= ((double) DAC_DECAY_SPEED) / gb->apu_output.sample_rate;
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if (gb->apu_output.dac_discharge[i] < 0) {
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multiplier = 0;
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gb->apu_output.dac_discharge[i] = 0;
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if (gb->model < GB_MODEL_AGB) {
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if (!is_DAC_enabled(gb, i)) {
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gb->apu_output.dac_discharge[i] -= ((double) DAC_DECAY_SPEED) / gb->apu_output.sample_rate;
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if (gb->apu_output.dac_discharge[i] < 0) {
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multiplier = 0;
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gb->apu_output.dac_discharge[i] = 0;
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}
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else {
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multiplier *= gb->apu_output.dac_discharge[i];
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}
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}
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else {
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multiplier *= gb->apu_output.dac_discharge[i];
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}
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}
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else {
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gb->apu_output.dac_discharge[i] += ((double) DAC_ATTACK_SPEED) / gb->apu_output.sample_rate;
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if (gb->apu_output.dac_discharge[i] > 1) {
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gb->apu_output.dac_discharge[i] = 1;
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}
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else {
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multiplier *= gb->apu_output.dac_discharge[i];
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gb->apu_output.dac_discharge[i] += ((double) DAC_ATTACK_SPEED) / gb->apu_output.sample_rate;
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if (gb->apu_output.dac_discharge[i] > 1) {
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gb->apu_output.dac_discharge[i] = 1;
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}
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else {
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multiplier *= gb->apu_output.dac_discharge[i];
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}
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}
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}
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