How to play multiple
audio files from ESP32
with MAX98357A

mkdir ~/myclips

ffmpeg -i ~/Videos/myvideo.mp4 -ss 00:01:23 -to 00:01:27 ~/myclips/clip1.wav

ffmpeg -i ~/mysound.wav -ss 00:01:23 -to 00:01:27 ~/myclips/clip1.wav

ffmpeg -i ~/Downloads/mysound.mp3 -ss 00:01:23 -to 00:01:27 ~/myclips/clip1.wav

ffmpeg -i ~/Videos/myvideo.mp4 -ss 00:01:23 -to 00:01:27 ~/myclips/clip1.wav

ffmpeg -i "/home/j/My Audio File.wav" -ss 00:01:23 -to 00:01:27 ~/myclips/clip1.wav

import sys, wave, struct

input_file  = sys.argv[1]
output_file = sys.argv[2]
var_name    = sys.argv[3] if len(sys.argv) > 3 else 'audio'

with wave.open(input_file, 'rb') as f:
    raw = f.readframes(f.getnframes())

samples = struct.unpack('<' + str(len(raw)//2) + 'h', raw)

lines = [
    '#pragma once',
    '#include <pgmspace.h>',
    'const int16_t ' + var_name + '_data[] PROGMEM = {',
]
chunks = [str(s) for s in samples]
for i in range(0, len(chunks), 16):
    lines.append('  ' + ', '.join(chunks[i:i+16]) + ',')
lines.append('};')
lines.append('const size_t ' + var_name + '_len = sizeof(' + var_name + '_data);')

with open(output_file, 'w') as f:
    f.write('\n'.join(lines) + '\n')

print('Done: ' + str(len(samples)) + ' samples -> ' + output_file)

for f in ~/myclips/*.wav; do
  name=$(basename "$f" .wav)
  ffmpeg -y -i "$f" -ar 22050 -ac 1 -acodec pcm_s16le "/tmp/${name}_i2s.wav"
  python3 ~/wav_to_i2s_header_multi.py "/tmp/${name}_i2s.wav" "${name}.h" "$name"
done

/*
 * We stand on the shoulders of giants when we build
 * with knowledge gained from others' efforts.
 * That doesn't make us giants. Be humble.
 * Create with care. Open source is the way.
 *
 * MAX98357A I2S - Multiple Clips, Auto Sequence
 * -----------------------------------------------
 * Plays all clips in order, repeating forever.
 *
 * Board:   ESP32 Dev Board (38-pin) or ESP32-C3
 * Amp:     MAX98357A
 *
 * Wiring (ESP32 Dev Board):
 *   BCLK -> GPIO27  LRC -> GPIO14  DIN -> GPIO13
 *
 * Wiring (ESP32-C3):
 *   BCLK -> GPIO4   LRC -> GPIO5   DIN -> GPIO6
 *
 * Open source - MIT Licence
 * Electronic Zoology - field notes from the garage
 * https://electroniczoology.com/guides/how-to-play-multiple-audio-files-esp32-max98357a
 */

#include <driver/i2s.h>
#include "clip1.h"
#include "clip2.h"
#include "clip3.h"
//#include "clip4.h"
//#include "clip5.h"
//#include "clip6.h"
//#include "clip7.h"
//#include "clip8.h"
//#include "clip9.h"
//#include "clip10.h"

// ESP32 Dev Board (38-pin)
#define I2S_BCLK    27
#define I2S_LRCLK   14
#define I2S_DOUT    13
// ESP32-C3 - comment out the three lines above and uncomment these:
//#define I2S_BCLK    4
//#define I2S_LRCLK   5
//#define I2S_DOUT    6

#define SAMPLE_RATE 22050  // must match -ar value used in ffmpeg conversion
#define VOLUME      0.8f
#define BUF_SAMPLES 256

int16_t i2s_buf[BUF_SAMPLES * 2];

struct Clip {
  const int16_t* data;
  size_t len;
};

// Add or remove rows to match your clips.
// Also update the #include lines above.
const Clip clips[] = {
  { clip1_data, clip1_len },
  { clip2_data, clip2_len },
  { clip3_data, clip3_len },
  //{ clip4_data, clip4_len },
  //{ clip5_data, clip5_len },
  //{ clip6_data, clip6_len },
  //{ clip7_data, clip7_len },
  //{ clip8_data, clip8_len },
  //{ clip9_data, clip9_len },
  //{ clip10_data, clip10_len },
};
const int CLIP_COUNT = sizeof(clips) / sizeof(clips[0]);

void playClip(const Clip& c) {
  size_t total = c.len / sizeof(int16_t);
  size_t written;
  for (size_t pos = 0; pos < total; pos += BUF_SAMPLES) {
    size_t count = min((size_t)BUF_SAMPLES, total - pos);
    for (size_t i = 0; i < count; i++) {
      int16_t s = (int16_t)(c.data[pos + i] * VOLUME);
      i2s_buf[i * 2]     = s;
      i2s_buf[i * 2 + 1] = s;
    }
    i2s_write(I2S_NUM_0, i2s_buf, count * 2 * sizeof(int16_t), &written, portMAX_DELAY);
  }
}

void setup() {
  i2s_config_t cfg = {
    .mode                 = (i2s_mode_t)(I2S_MODE_MASTER | I2S_MODE_TX),
    .sample_rate          = SAMPLE_RATE,
    .bits_per_sample      = I2S_BITS_PER_SAMPLE_16BIT,
    .channel_format       = I2S_CHANNEL_FMT_RIGHT_LEFT,
    .communication_format = I2S_COMM_FORMAT_STAND_I2S,
    .intr_alloc_flags     = ESP_INTR_FLAG_LEVEL1,
    .dma_buf_count        = 8,
    .dma_buf_len          = 64,
    .use_apll             = false,
    .tx_desc_auto_clear   = true,
  };
  i2s_pin_config_t pins = {
    .bck_io_num   = I2S_BCLK,
    .ws_io_num    = I2S_LRCLK,
    .data_out_num = I2S_DOUT,
    .data_in_num  = I2S_PIN_NO_CHANGE,
  };
  i2s_driver_install(I2S_NUM_0, &cfg, 0, NULL);
  i2s_set_pin(I2S_NUM_0, &pins);
}

void loop() {
  for (int i = 0; i < CLIP_COUNT; i++) {
    playClip(clips[i]);
    delay(500);
  }
}