[sgu] Generate 48kHz sample, resample to sokol samplerate later

Author: smokku

src/chips/sgu1.c

@@ -21,41 +21,34 @@
 void sgu1_init(sgu1_t* sgu, const sgu1_desc_t* desc) {
     CHIPS_ASSERT(sgu && desc);
     CHIPS_ASSERT(desc->tick_hz > 0);
-    CHIPS_ASSERT(desc->sound_hz > 0);
     memset(sgu, 0, sizeof(*sgu));
-    sgu->sound_hz = desc->sound_hz;
-    sgu->sample_period = (desc->tick_hz * SGU1_FIXEDPOINT_SCALE) / desc->sound_hz;
-    sgu->sample_counter = sgu->sample_period;
     sgu->sample_mag = desc->magnitude;
     sgu->tick_period = (desc->tick_hz * SGU1_FIXEDPOINT_SCALE) / SGU1_CHIP_CLOCK;
     sgu->tick_counter = sgu->tick_period;
     SoundUnit_Init(&sgu->su, 65536);
-    sgu->resampler = speex_resampler_init(SGU1_AUDIO_CHANNELS, SGU1_CHIP_CLOCK, sgu->sound_hz, 10, nullptr);
 }
 
 void sgu1_reset(sgu1_t* sgu) {
     CHIPS_ASSERT(sgu);
     SoundUnit_Reset(&sgu->su);
     memset(sgu->reg, 0, sizeof(sgu->reg));
     sgu->tick_counter = sgu->tick_period;
-    sgu->sample_counter = sgu->sample_period;
     sgu->sample[0] = sgu->sample[1] = 0.0f;
     sgu->pins = 0;
-    speex_resampler_reset_mem(sgu->resampler);
 }
 
 /* tick the sound generation, return true when new sample ready */
 static uint64_t _sgu1_tick(sgu1_t* sgu, uint64_t pins) {
+    pins &= ~SGU1_SAMPLE;
     /* next sample? */
     sgu->tick_counter -= SGU1_FIXEDPOINT_SCALE;
     while (sgu->tick_counter <= 0) {
         sgu->tick_counter += sgu->tick_period;
         int32_t l, r;
         SoundUnit_NextSample(&sgu->su, &l, &r);
-        float in[2] = { ((float)l / 32767.0f), ((float)r / 32767.0f) };
-        spx_uint32_t in_len = 1;   // 1 stereo frame
-        spx_uint32_t out_len = 1;  // room for 1 stereo frame
-        speex_resampler_process_interleaved_float(sgu->resampler, in, &in_len, sgu->sample, &out_len);
+        sgu->sample[0] = sgu->sample_mag * (float)l / 32767.0f;
+        sgu->sample[1] = sgu->sample_mag * (float)r / 32767.0f;
+        pins |= SGU1_SAMPLE;
 
         for (uint8_t i = 0; i < SGU1_NUM_CHANNELS; i++) {
             sgu->voice[i].sample_buffer[sgu->voice[i].sample_pos++] = (float)(SoundUnit_GetSample(&sgu->su, i));
@@ -64,16 +57,6 @@ static uint64_t _sgu1_tick(sgu1_t* sgu, uint64_t pins) {
             }
         }
     }
-
-    /* new sample? */
-    pins &= ~SGU1_SAMPLE;
-    sgu->sample_counter -= SGU1_FIXEDPOINT_SCALE;
-    while (sgu->sample_counter <= 0) {
-        sgu->sample_counter += sgu->sample_period;
-        sgu->sample[0] = sgu->sample_mag * sgu->sample[0];
-        sgu->sample[1] = sgu->sample_mag * sgu->sample[1];
-        pins |= SGU1_SAMPLE;
-    }
     return pins;
 }
 

src/chips/sgu1.h

@@ -170,12 +170,11 @@ extern "C" {
 #define SGU1_VOL_SWEEP_BOUNCE (1 << 7)
 
 #define SGU1_AUDIO_CHANNELS (2)
-#define SGU1_AUDIO_SAMPLES  (4096)
+#define SGU1_AUDIO_SAMPLES  (1024)
 
 // setup parameters for sgu1_init()
 typedef struct {
     int tick_hz;      // frequency at which sgu1_tick() will be called in Hz
-    int sound_hz;     // sound sample frequency
     float magnitude;  // output sample magnitude (0=silence to 1=max volume)
 } sgu1_desc_t;
 
@@ -187,10 +186,7 @@ typedef struct {
     uint8_t reg[32];
     int tick_period;
     int tick_counter;
-    SpeexResamplerState* resampler;
     // sample generation state
-    int sample_period;
-    int sample_counter;
     float sample_mag;
     float sample[SGU1_AUDIO_CHANNELS];  // Left, Right
     // voice visualization

src/systems/x65.c

@@ -64,7 +64,6 @@ void x65_init(x65_t* sys, const x65_desc_t* desc) {
         &sys->sgu,
         &(sgu1_desc_t){
             .tick_hz = X65_FREQUENCY,
-            .sound_hz = _X65_DEFAULT(desc->audio.sample_rate, 44100),
             .magnitude = _X65_DEFAULT(desc->audio.volume, 1.0f),
         });
     beeper_init(

src/x65.c

@@ -68,6 +68,7 @@ static struct {
     } dbg;
     x65_snapshot_t snapshots[UI_SNAPSHOT_MAX_SLOTS];
 #endif
+    SpeexResamplerState* resampler;
 } state;
 
 #ifdef CHIPS_USE_UI
@@ -110,7 +111,11 @@ static void* labels = NULL;
 // audio-streaming callback
 static void push_audio(const float* samples, int num_samples, void* user_data) {
     (void)user_data;
-    saudio_push(samples, num_samples / X65_AUDIO_CHANNELS);
+    spx_uint32_t in_len = num_samples / X65_AUDIO_CHANNELS;
+    spx_uint32_t out_len = X65_MAX_AUDIO_SAMPLES;
+    static float buf[X65_MAX_AUDIO_SAMPLES];
+    speex_resampler_process_interleaved_float(state.resampler, samples, &in_len, buf, &out_len);
+    saudio_push(buf, out_len);
 }
 
 // get x65_desc_t struct based on joystick type
@@ -146,12 +151,15 @@ static void app_load_rom_labels(const char* rom_file) {
     }
 #endif
 }
+#define SGU_CHIP_CLOCK (48000)
 
 void app_init(void) {
     saudio_setup(&(saudio_desc){
+        .sample_rate = SGU_CHIP_CLOCK,
         .num_channels = X65_AUDIO_CHANNELS,
         .logger.func = slog_func,
     });
+    state.resampler = speex_resampler_init(SGU1_AUDIO_CHANNELS, SGU_CHIP_CLOCK, saudio_sample_rate(), 4, 0);
     x65_joystick_type_t joy_type = arguments.joy ? X65_JOYSTICKTYPE_DIGITAL_1 : X65_JOYSTICKTYPE_NONE;
     if (sargs_exists("joystick")) {
         if (sargs_equals("joystick", "digital_1")) {
@@ -354,6 +362,7 @@ void app_cleanup(void) {
     ui_discard();
 #endif
     saudio_shutdown();
+    speex_resampler_destroy(state.resampler);
     gfx_shutdown();
     sargs_shutdown();
     hid_shutdown();