How to play audio from
ESP32 with PAM8403

espeak-ng -w /tmp/myclip.wav "your text here"

ffmpeg -i /path/to/source.wav -ss 00:00:05 -to 00:00:08 /tmp/myclip.wav

ffmpeg -i ~/mysound.wav -ss 00:00:05 -to 00:00:08 /tmp/myclip.wav

ffmpeg -i ~/Downloads/mysound.mp3 -ss 00:00:05 -to 00:00:08 /tmp/myclip.wav

ffmpeg -i ~/Videos/myvideo.mp4 -ss 00:00:05 -to 00:00:08 /tmp/myclip.wav

ffmpeg -i "/home/j/My Audio File.wav" -ss 00:00:05 -to 00:00:08 /tmp/myclip.wav

ffmpeg -y -i /tmp/myclip.wav -ar 8000 -ac 1 -acodec pcm_u8 /tmp/myclip_8bit.wav

import sys

input_file = sys.argv[1]   # e.g. /tmp/myclip_8bit.wav
output_file = sys.argv[2]  # e.g. myclip.h
var_name = sys.argv[3]     # e.g. myclip

with open(input_file, 'rb') as f:
    data = f.read()

pcm = data[44:]  # skip 44-byte WAV header

lines = [
    '#pragma once',
    '#include <pgmspace.h>',
    f'const uint32_t {var_name}_len = {len(pcm)};',
    f'const uint8_t {var_name}_data[] PROGMEM = {{'
]

row = []
for b in pcm:
    row.append(f'0x{b:02X}')
    if len(row) == 16:
        lines.append('  ' + ', '.join(row) + ',')
        row = []
if row:
    lines.append('  ' + ', '.join(row))
lines.append('};')

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

print(f"Done: {len(pcm)} bytes -> {output_file}")

python3 wav_to_header.py /tmp/myclip_8bit.wav myclip.h myclip

/*
 * 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.
 *
 * PAM8403 Audio Amplifier with ESP32 - WAV Playback
 * --------------------------------------------------
 * Plays a WAV clip stored as a C byte array via the
 * ESP32 built-in DAC (GPIO25) into a PAM8403 class-D
 * amplifier module.
 *
 * Open source - MIT Licence
 * Built with reference to the Espressif ESP32 Arduino
 * core DAC and PROGMEM examples.
 *
 * Electronic Zoology - field notes from the garage
 * https://electroniczoology.com
 */

#include "myclip.h"  // generated from wav_to_header.py

const int DAC_PIN     = 25;
const int SAMPLE_RATE = 8000;
const float VOLUME    = 0.8;  // 0.0 = silent, 1.0 = max

void playAudio() {
  uint32_t intervalUs = 1000000 / SAMPLE_RATE;
  for (uint32_t i = 0; i < myclip_len; i++) {
    uint8_t sample = pgm_read_byte(&myclip_data[i]);
    // Scale around midpoint to control volume
    int val = 128 + (int)((sample - 128) * VOLUME);
    val = constrain(val, 0, 255);
    dacWrite(DAC_PIN, val);
    delayMicroseconds(intervalUs);
  }
  dacWrite(DAC_PIN, 128); // return to midpoint (silence)
}

void setup() {
  playAudio();
}

void loop() {
  // Nothing here - clip plays once on boot.
  // Reset the ESP32 to play again.
}