BirdNet-goMikrofon/Arduino-audio-tools-main/arduino-audio-tools-main/examples/examples-communication/http-server/streams-generator-webserver_adpcm

Webserver with ADPCM Encoding

This is a variant of streams-generator-webserver_wav that encodes the generated sine wave as IMA/DVI ADPCM instead of plain PCM before serving it as a WAV stream. Since ADPCM only needs 4 bits per sample instead of 16, this reduces the required bandwidth to about a quarter - useful e.g. when streaming over a slow or congested WiFi connection.

You can register any AudioEncoderExt based ADPCM encoder (MS, IMA/DVI, Yamaha) with the WAVEncoder that is used internally by AudioWAVServer:

server.wavEncoder().setEncoder(adpcmEncoder, AudioFormat::DVI_ADPCM);

This also automatically writes the extended fmt /fact chunks that ADPCM WAV files need (equivalent to calling setExtADPCMHeader(true)); call setExtADPCMHeader(false) afterward if you explicitly want the plain 16-byte header instead.

Note: this will not play in Chrome (or most browsers)

Unlike the plain PCM streams-generator-webserver_wav example, this one will not produce sound when opened directly in Chrome or most other browsers: their built-in WAV decoder only understands plain PCM (and IEEE float/A-law/µ-law) - not ADPCM-compressed WAV data. To actually hear the stream, use a client capable of decoding ADPCM instead, e.g.:

• ffplay http://<esp32-ip>/
• VLC, pointed at the URL
• An ESP32/AudioTools client using ADPCMDecoder to decode the stream (the actual use case for the bandwidth savings)