decoder.h File Reference

Audio file decoder: turns an MP3 or WAV file into interleaved PCM frames. More...

#include "esp_err.h"
#include <stdint.h>
#include <stddef.h>

Go to the source code of this file.

Data Structures
struct	decoder_format_t
	PCM format of the open stream, read once after decoder_open(). More...

Macros
#define	DECODER_READ_BUF_BYTES   (2304 * 4)
	Largest number of PCM bytes a single decoder_read() can emit.

Functions
esp_err_t	decoder_open (const char *path)
	Open an audio file, pick the backend, and read its format.
esp_err_t	decoder_format (decoder_format_t *fmt)
	Get the PCM format of the open stream.
esp_err_t	decoder_read (void *pcm, size_t cap_bytes, size_t *got_bytes)
	Decode the next chunk of audio into pcm.
esp_err_t	decoder_close (void)
	Close the stream and free the decoder. Safe to call when nothing is open.

Detailed Description

Audio file decoder: turns an MP3 or WAV file into interleaved PCM frames.

The mirror image of Audio sink interface on the input side. The public API is a concrete facade: decoder_open() auto-detects the format (by extension, confirmed by the file's magic bytes) and routes to the matching backend (libhelix MP3 or raw WAV). The caller never sees which backend is active; it just reads PCM until end of file.

Output layout is always 32-bit MSB-justified words (4 bytes per sample), ready to hand straight to sink->write(): 16-bit sources sit in the high 16 bits, 24-bit sources in the high 24 bits. The format's bits field reports the source width only. Always interleaved stereo (mono sources are up-mixed L=R), so the wired sink's fixed stereo slots stay full.

One stream at a time: decoder_open() while a stream is already open returns an error.

Note

Développé avec l'assistance de Claude Opus 4.8 (Anthropic), sous la direction de Y. Dos Santos : spécification, revue et validation sur cible par l'auteur.