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SB: fix SBPro stereo mode

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wbcbz7 committed 2026-03-19 02:00:56 +07:00
1 parent 75d5e6f443
commit 606a073133
2 files changed
+40 -34
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sw/sbdsp/sbdsp.cpp
+39 -34
View File
@@ -195,13 +195,14 @@ uint32_t sbdsp_generate_sample() {
static __force_inline void sbdsp_set_dma_interval() {
if (sbdsp.sample_rate) {
sbdsp.dma_interval = 1000000000ul / sbdsp.sample_rate / 1000;
sbdsp.rateratio = (44100 << SB_RSM_FRAC) / sbdsp.sample_rate;
uint32_t actual_sr = (sbdsp.sample_rate >> (sbdsp.dma_stereo_sbpro ? 1 : 0));
sbdsp.dma_interval = 1000000000ul / actual_sr / 1000;
sbdsp.rateratio = (44100 << SB_RSM_FRAC) / actual_sr;
} else {
sbdsp.dma_interval = 256 - sbdsp.time_constant;
sbdsp.dma_interval = (256 - sbdsp.time_constant) << (sbdsp.dma_stereo_sbpro ? 1 : 0);
sbdsp.rateratio = (44100 << SB_RSM_FRAC) / (1000000ul / sbdsp.dma_interval);
}
// No halving for stereo/16-bit: dma_write_multi transfers a complete
// No halving for stereo/16-bit (unless SBPro stereo): dma_write_multi transfers a complete
// frame per event, so the interval is always one sample period.
}
@@ -288,6 +289,29 @@ static __force_inline void sbdsp_output(uint8_t value) {
sbdsp.dav_pc = 1;
}
// start pre-SB16 PCM DMA transfer
// TODO: Creative ADPCM?
static void sbdsp_start_pcm_dma(int autoinit, uint16_t xfer_size) {
sbdsp.autoinit = autoinit;
bool dma_stereo = (mixer_state[0x0E] & 2);
if (dma_stereo && ((xfer_size + 1) == 1)) {
// HACK: many SBPro programs follow Creative's documentation and perform 1 byte single-cycle
// DMA transfer to seemingly reset the mixer stereo state, then waiting for IRQ to come.
// since the sbdsp.dma_xfer_count calculation divides by 2 for stereo case, it results in
// xfer_count==0, so the transfer never actually occurs.
// for those transfers, force mono mode.
dma_stereo = false;
}
sbdsp.dma_stereo = dma_stereo;
sbdsp.dma_stereo_sbpro = dma_stereo;
sbdsp.dma_bytes_per_frame = sbdsp.dma_stereo ? 2 : 1;
sbdsp.dma_xfer_count = (xfer_size + 1) / sbdsp.dma_bytes_per_frame;
sbdsp.dma_xfer_count_left = sbdsp.dma_xfer_count;
sbdsp_set_dma_interval();
sbdsp.dma_done = false;
sbdsp_dma_enable();
}
void sbdsp_process(void) {
if (sbdsp.reset_state) return;
@@ -323,25 +347,14 @@ void sbdsp_process(void) {
sbdsp.current_command = 0;
break;
case DSP_DMA_AUTO:
sbdsp.autoinit = 1;
sbdsp.dma_bytes_per_frame = sbdsp.dma_stereo ? 2 : 1;
sbdsp.dma_xfer_count = (sbdsp.dma_block_size + 1) / sbdsp.dma_bytes_per_frame;
sbdsp.dma_xfer_count_left = sbdsp.dma_xfer_count;
sbdsp_set_dma_interval();
sbdsp.dma_done = false;
sbdsp_dma_enable();
sbdsp.current_command = 0;
sbdsp.dav_dsp = 0;
sbdsp.current_command = 0;
sbdsp_start_pcm_dma(1, sbdsp.dma_block_size);
break;
case DSP_DMA_HS_AUTO:
sbdsp.dav_dsp = 0;
sbdsp.autoinit = 1;
sbdsp.dma_bytes_per_frame = sbdsp.dma_stereo ? 2 : 1;
sbdsp.dma_xfer_count = (sbdsp.dma_block_size + 1) / sbdsp.dma_bytes_per_frame;
sbdsp.dma_xfer_count_left = sbdsp.dma_xfer_count;
sbdsp_set_dma_interval();
sbdsp.dma_done = false;
sbdsp_dma_enable();
sbdsp.current_command = 0;
sbdsp_start_pcm_dma(1, sbdsp.dma_block_size);
break;
case DSP_SET_TIME_CONSTANT:
@@ -349,6 +362,7 @@ void sbdsp_process(void) {
if (sbdsp.current_command_index == 1) {
sbdsp.time_constant = sbdsp.inbox;
sbdsp.sample_rate = 0; // Rate of 0 indicates time constant drives DMA timing
sbdsp_set_dma_interval();
sbdsp.dav_dsp = 0;
sbdsp.current_command = 0;
}
@@ -363,6 +377,7 @@ void sbdsp_process(void) {
} else if (sbdsp.current_command_index == 2) { // wSamplingRate.LowByte
sbdsp.sample_rate |= sbdsp.inbox;
sbdsp.time_constant = 0;
sbdsp_set_dma_interval();
sbdsp.dav_dsp = 0;
sbdsp.current_command = 0;
}
@@ -386,13 +401,7 @@ void sbdsp_process(void) {
case DSP_DMA_HS_SINGLE:
sbdsp.dav_dsp = 0;
sbdsp.current_command = 0;
sbdsp.autoinit = 0;
sbdsp.dma_bytes_per_frame = sbdsp.dma_stereo ? 2 : 1;
sbdsp.dma_xfer_count = (sbdsp.dma_block_size + 1) / sbdsp.dma_bytes_per_frame;
sbdsp.dma_xfer_count_left = sbdsp.dma_xfer_count;
sbdsp_set_dma_interval();
sbdsp.dma_done = false;
sbdsp_dma_enable();
sbdsp_start_pcm_dma(0, sbdsp.dma_block_size);
break;
case DSP_DMA_SINGLE:
if (sbdsp.dav_dsp) {
@@ -403,13 +412,7 @@ void sbdsp_process(void) {
sbdsp.dma_sample_count += (sbdsp.inbox << 8);
sbdsp.dav_dsp = 0;
sbdsp.current_command = 0;
sbdsp.autoinit = 0;
sbdsp.dma_bytes_per_frame = sbdsp.dma_stereo ? 2 : 1;
sbdsp.dma_xfer_count = (sbdsp.dma_sample_count + 1) / sbdsp.dma_bytes_per_frame;
sbdsp.dma_xfer_count_left = sbdsp.dma_xfer_count;
sbdsp_set_dma_interval();
sbdsp.dma_done = false;
sbdsp_dma_enable();
sbdsp_start_pcm_dma(0, sbdsp.dma_sample_count);
}
sbdsp.current_command_index++;
}
@@ -542,12 +545,14 @@ void sbdsp_process(void) {
}
break;
case DSP_DMA_IO_START ... DSP_DMA_IO_END:
// SB16 DMA transfer
if (sbdsp.dav_dsp) {
if (sbdsp.current_command_index == 0) { // bCommand + bMode
sbdsp.dma_16bit = (sbdsp.current_command & 0xf0) == 0xb0;
sbdsp.autoinit = sbdsp.current_command & 0x4;
sbdsp.dma_signed = sbdsp.inbox & 0x10;
sbdsp.dma_stereo = sbdsp.inbox & 0x20;
sbdsp.dma_stereo_sbpro = 0;
sbdsp.dav_dsp = 0;
} else if (sbdsp.current_command_index == 1) { // wLength.LowByte
sbdsp.dma_sample_count = sbdsp.inbox;
@@ -695,7 +700,7 @@ static __force_inline void sbmixer_write(uint8_t value) {
case 0xFF:
break;
case MIXER_STEREO:
sbdsp.dma_stereo = value & 2;
//sbdsp.dma_stereo = value & 2;
// no break
default:
mixer_state[sbdsp.mixer_command] = value;
sw/sbdsp/sbdsp.h
+1
View File
@@ -60,6 +60,7 @@ typedef struct sbdsp_t {
bool dma_enabled;
bool dma_16bit;
bool dma_stereo;
bool dma_stereo_sbpro;
bool dma_signed;
volatile bool dma_done;