{"id":5681,"date":"2023-05-21T06:48:27","date_gmt":"2023-05-21T04:48:27","guid":{"rendered":"https:\/\/www.pschatzmann.ch\/home\/?p=5681"},"modified":"2025-04-10T18:52:30","modified_gmt":"2025-04-10T16:52:30","slug":"adpcm-and-wav-files","status":"publish","type":"post","link":"https:\/\/www.pschatzmann.ch\/home\/2023\/05\/21\/adpcm-and-wav-files\/","title":{"rendered":"ADPCM and WAV Files"},"content":{"rendered":"

At the very beginning of my Arduino AudioTools<\/a> project, I was providing a codec for WAV files. It was just handling PCM audio, so it just needed to read or write the header and then could just copy the audio data.<\/p>\n

In my last blog<\/a>, I was writing that the ADPCM codec is perfectly suited for encoding and decoding audio on microcontrollers. So the next natural step is to provide a proper ADPCM support for WAV files<\/strong> and that’s what I have implemented this week.<\/p>\n

Arduino Sketch<\/h2>\n

Here is a test sketch that encodes and decodes a sine test signal using the Microsoft ADPCM WAV format.<\/p>\n

#include \"AudioTools.h\"\n#include \"AudioTools\/AudioCodecs\/CodecWAV.h\" \n#include \"AudioTools\/AudioCodecs\/CodecADPCM.h\"\n\nAudioInfo info(16000, 2, 16);\nSineWaveGenerator<int16_t> sineWave( 32000);  \nGeneratedSoundStream<int16_t> sound( sineWave); \nCsvStream<int16_t> out(Serial);\nADPCMDecoder adpcm_decoder(AV_CODEC_ID_ADPCM_IMA_WAV); \nADPCMEncoder adpcm_encoder(AV_CODEC_ID_ADPCM_IMA_WAV);  \nWAVDecoder wav_decoder(adpcm_decoder, AudioFormat::ADPCM);\nWAVEncoder wav_encoder(adpcm_encoder, AudioFormat::ADPCM)\nEncodedAudioStream decoder(&out, &wav_decoder); \nEncodedAudioStream encoder(&decoder, &wav_encoder); \nStreamCopy copier(encoder, sound);     \n\nvoid setup() {\n  Serial.begin(115200);\n  AudioLogger::instance().begin(Serial, AudioLogger::Warning);\n\n  \/\/ start Output\n  auto cfgi = out.defaultConfig(TX_MODE);\n  cfgi.copyFrom(info);\n  out.begin(cfgi);\n\n  \/\/ Setup sine wave\n  auto cfgs = sineWave.defaultConfig();\n  cfgs.copyFrom(info);\n  sineWave.begin(info, N_B4);\n\n  \/\/ start decoder\n  decoder.begin(info);\n\n  \/\/ start encoder\n  encoder.begin(info);\n}\n\nvoid loop() { \n  copier.copy();\n}\n<\/code><\/pre>\n
When we create the WAVEncoder<\/a> we just need to give it an encoder and the corresponding WAV format as arguments. The same applies for the WAVDecoder<\/a>.<\/p>\n
Summary<\/h2>\n
Now, we can easily provide compressed audio with the help of WAV files.<\/p>\n
Dependencies<\/h2>\n
Do not forget to install the following libraries:<\/p>\n