test_opus.cpp

 #include <Arduino.h>

 #include <FS.h>
 #include <i2s.h>
 #include <opusfile_spiffs.hpp>


#define SAMPLE_RATE_HZ (32000)

 void setup() {
   Serial.begin(115200);

   SPIFFS.begin();
   i2s_set_rate(SAMPLE_RATE_HZ);
   i2s_init();
 }

 void play_opus() {
     Serial.printf("play with i2s_get_buffer() at %d hz\n", SAMPLE_RATE_HZ);
     Palatis::OpusFileSPIFFS audio = Palatis::OpusFileSPIFFS("/test.opus");
     // Serial.printf("file is %d bytes\n", audio.size());

     i2s_begin();

     time_t time1 = micros();
     size_t pos = 0;
     size_t total = SAMPLE_RATE_HZ * 4;
     size_t delayed = 0;
     while (audio.available()) {
         uint32_t * buf;
         time_t time3 = micros();
         while ((buf = i2s_get_buffer()) == nullptr)
             delay(0); // make the watchdog happy
         time_t time4 = micros();
         delayed += time4 - time3;

         int num = audio.read_stereo(reinterpret_cast<opus_int16 *>(buf), 64 * 2);
         i2s_put_buffer();

         pos += num * 2;

         if (pos >= total) {
             time_t time2 = micros();
             total += SAMPLE_RATE_HZ * 4;
             Serial.printf("read %d bytes, took %.03f ms, idled %.03f ms, i2s %.03f ms, free heap %d bytes\n",
                 pos, (time2 - time1) / 1000.0, delayed / 1000.0, ((time2 - time1) - delayed) / 1000.0, ESP.getFreeHeap());
             time1 = time2;
             delayed = 0;
         }
     }

  i2s_end();
}

void loop() {
  time_t time1, time2;

  time1 = millis();
  play_opus();
  time2 = millis();
  Serial.printf("free %d bytes, total %d ms\n", ESP.getFreeHeap(), time2 - time1);

  delay(10000);
}