mp3_frame.h File Reference

Internal MPEG-1/2 Layer III header + VBR-tag (Xing/Info/VBRI) parsing. More...

#include <stdint.h>
#include <stdbool.h>
#include <stddef.h>

Go to the source code of this file.

Data Structures
struct	mp3_frame_hdr_t
	Decoded fields of one MPEG Layer III frame header. More...

Functions
bool	mp3_frame_parse (const uint8_t *p, size_t len, mp3_frame_hdr_t *out)
	Parse a 4-byte MPEG Layer III frame header at p.
uint32_t	mp3_xing_duration_ms (const uint8_t *frame, size_t len, const mp3_frame_hdr_t *hdr)
	Track duration from a Xing/Info/VBRI tag in the first frame, if present.

Detailed Description

Internal MPEG-1/2 Layer III header + VBR-tag (Xing/Info/VBRI) parsing.

Not a public header: shared by the MP3 decoder backend (decoder_mp3.c, for the playing stream's duration) and the track-metadata reader (track_meta.c, for bitrate + duration). Pure byte math with no ESP-IDF or libhelix dependency, so the duration logic lives in one place and is host-testable on its own.

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.

Function Documentation

mp3_frame_parse()

bool mp3_frame_parse	(	const uint8_t *	p,
		size_t	len,
		mp3_frame_hdr_t *	out )

Parse a 4-byte MPEG Layer III frame header at p.

Parameters

p	Candidate frame start (the 0xFF sync byte).
len	Bytes readable from p (must be >= 4).
out	Filled on success.

Returns

true if p holds a valid Layer III header; false otherwise.

mp3_xing_duration_ms()

uint32_t mp3_xing_duration_ms	(	const uint8_t *	frame,
		size_t	len,
		const mp3_frame_hdr_t *	hdr )

Track duration from a Xing/Info/VBRI tag in the first frame, if present.

Parameters

frame	First frame start (its 0xFF sync byte).
len	Bytes readable from frame.
hdr	Header already parsed by mp3_frame_parse() for frame.

Returns

Duration in ms, or 0 when no usable VBR tag is present (duration unknown).