Merge pull request #837 from Daft-Freak/pico-audio-improvements

Pico audio improvements
32blit · Sep 28, 2023 · 657ef83 · 657ef83
2 parents 2f6b9ad + 1b5d026
commit 657ef83
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Showing 4 changed files with 69 additions and 16 deletions.
diff --git a/32blit-pico/audio_i2s.cpp b/32blit-pico/audio_i2s.cpp
@@ -12,6 +12,8 @@
 
 static audio_buffer_pool *audio_pool = nullptr;
 
+static struct audio_buffer *cur_buffer = nullptr;
+
 void init_audio() {
   static audio_format_t audio_format = {
     .sample_freq = AUDIO_SAMPLE_FREQ,
@@ -24,7 +26,7 @@ void init_audio() {
     .sample_stride = 2
   };
 
-  struct audio_buffer_pool *producer_pool = audio_new_producer_pool(&producer_format, 4, 441);
+  struct audio_buffer_pool *producer_pool = audio_new_producer_pool(&producer_format, 4, 256);
   const struct audio_format *output_format;
 
   uint8_t dma_channel = dma_claim_unused_channel(true);
@@ -54,18 +56,34 @@ void init_audio() {
 }
 
 void update_audio(uint32_t time) {
-  // audio
-  struct audio_buffer *buffer = take_audio_buffer(audio_pool, false);
-  if(buffer) {
-    auto samples = (int16_t *) buffer->buffer->bytes;
+  // attempt to get new buffer
+  if(!cur_buffer) {
+    cur_buffer = take_audio_buffer(audio_pool, false);
+    if(cur_buffer)
+      cur_buffer->sample_count = 0;
+  }
+
+  if(cur_buffer) {
+    auto samples = ((int16_t *)cur_buffer->buffer->bytes) + cur_buffer->sample_count;
+
+    auto max_samples = cur_buffer->max_sample_count - cur_buffer->sample_count;
 
-    for(uint32_t i = 0; i < buffer->max_sample_count; i += 2) {
+#ifdef AUDIO_MAX_SAMPLE_UPDATE
+    if(max_samples > AUDIO_MAX_SAMPLE_UPDATE)
+      max_samples = AUDIO_MAX_SAMPLE_UPDATE;
+#endif
+
+    for(uint32_t i = 0; i < max_samples; i += 2) {
       int val = (int)blit::get_audio_frame() - 0x8000;
       *samples++ = val;
       *samples++ = val;
     }
 
-    buffer->sample_count = buffer->max_sample_count;
-    give_audio_buffer(audio_pool, buffer);
+    cur_buffer->sample_count += max_samples;
+
+    if(cur_buffer->sample_count == cur_buffer->max_sample_count) {
+      give_audio_buffer(audio_pool, cur_buffer);
+      cur_buffer = nullptr;
+    }
   }
 }
diff --git a/32blit-pico/audio_pwm.cpp b/32blit-pico/audio_pwm.cpp
@@ -14,6 +14,8 @@
 
 static audio_buffer_pool *audio_pool = nullptr;
 
+static struct audio_buffer *cur_buffer = nullptr;
+
 void init_audio() {
   static audio_format_t audio_format = {
     .sample_freq = AUDIO_SAMPLE_FREQ,
@@ -62,17 +64,28 @@ void init_audio() {
 }
 
 void update_audio(uint32_t time) {
-  // audio
-  struct audio_buffer *buffer = take_audio_buffer(audio_pool, false);
-  if(buffer) {
-    auto samples = (int16_t *) buffer->buffer->bytes;
+  // attempt to get new buffer
+  if(!cur_buffer) {
+    cur_buffer = take_audio_buffer(audio_pool, false);
+    if(cur_buffer)
+      cur_buffer->sample_count = 0;
+  }
+
+  if(cur_buffer) {
+    auto samples = ((int16_t *)cur_buffer->buffer->bytes) + cur_buffer->sample_count;
 
-    for(uint32_t i = 0; i < buffer->max_sample_count; i++) {
+    auto max_samples = cur_buffer->max_sample_count - cur_buffer->sample_count;
+
+    for(uint32_t i = 0; i < max_samples; i++) {
       int val = (int)blit::get_audio_frame() - 0x8000;
       *samples++ = val;
     }
 
-    buffer->sample_count = buffer->max_sample_count;
-    give_audio_buffer(audio_pool, buffer);
+    cur_buffer->sample_count += max_samples;
+
+    if(cur_buffer->sample_count == cur_buffer->max_sample_count) {
+      give_audio_buffer(audio_pool, cur_buffer);
+      cur_buffer = nullptr;
+    }
   }
 }
diff --git a/32blit-pico/board/vgaboard/config.h b/32blit-pico/board/vgaboard/config.h
@@ -4,6 +4,8 @@
 #define ALLOW_HIRES 0 // disable by default, mode switching isn't supported
 #endif
 
+#define AUDIO_MAX_SAMPLE_UPDATE 64
+
 // spi
 #define SD_SCK   5
 #define SD_MOSI 18

diff --git a/32blit-pico/main.cpp b/32blit-pico/main.cpp
@@ -2,6 +2,7 @@
 
 #include "hardware/structs/rosc.h"
 #include "hardware/vreg.h"
+#include "hardware/timer.h"
 #include "pico/binary_info.h"
 #include "pico/multicore.h"
 #include "pico/rand.h"
@@ -104,18 +105,30 @@ void update(uint32_t);
 
 bool core1_started = false;
 
+#ifdef ENABLE_CORE1
 void core1_main() {
   core1_started = true;
   multicore_lockout_victim_init();
 
   init_display_core1();
+  init_audio();
 
   while(true) {
     update_display_core1();
+    update_audio(::now());
     sleep_us(1);
   }
 }
 
+#else
+static void alarm_callback(uint alarm_num) {
+  update_audio(::now());
+
+  timer_hw->intr = 1 << alarm_num;
+  hardware_alarm_set_target(alarm_num, make_timeout_time_ms(5));
+}
+#endif
+
 int main() {
 #if OVERCLOCK_250
   // Apply a modest overvolt, default is 1.10v.
@@ -185,10 +198,18 @@ int main() {
   init_input();
   init_fs();
   init_usb();
+#if !defined(ENABLE_CORE1)
   init_audio();
+#endif
 
 #if defined(ENABLE_CORE1)
   multicore_launch_core1(core1_main);
+#else
+  // fallback audio timer if core1 is unavailable / not enabled
+  int alarm_num = hardware_alarm_claim_unused(true);
+  hardware_alarm_set_callback(alarm_num, alarm_callback);
+  hardware_alarm_set_target(alarm_num, make_timeout_time_ms(5));
+  irq_set_priority(TIMER_IRQ_0 + alarm_num, PICO_LOWEST_IRQ_PRIORITY);
 #endif
 
   blit::set_screen_mode(ScreenMode::lores);
@@ -204,7 +225,6 @@ int main() {
     update_display(now);
     update_input();
     int ms_to_next_update = tick(::now());
-    update_audio(now);
     update_led();
     update_usb();
     update_multiplayer();