Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
Fetching contributors…

Cannot retrieve contributors at this time

77 lines (66 sloc) 2.325 kb
/*
* MPEG Audio header decoder
* Copyright (c) 2001, 2002 Fabrice Bellard
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file
* MPEG Audio header decoder.
*/
#ifndef AVCODEC_MPEGAUDIODECHEADER_H
#define AVCODEC_MPEGAUDIODECHEADER_H
#include "avcodec.h"
#define MP3_MASK 0xFFFE0CCF
#define MPA_DECODE_HEADER \
int frame_size; \
int error_protection; \
int layer; \
int sample_rate; \
int sample_rate_index; /* between 0 and 8 */ \
int bit_rate; \
int nb_channels; \
int mode; \
int mode_ext; \
int lsf;
typedef struct MPADecodeHeader {
MPA_DECODE_HEADER
} MPADecodeHeader;
/* header decoding. MUST check the header before because no
consistency check is done there. Return 1 if free format found and
that the frame size must be computed externally */
int avpriv_mpegaudio_decode_header(MPADecodeHeader *s, uint32_t header);
/* useful helper to get mpeg audio stream infos. Return -1 if error in
header, otherwise the coded frame size in bytes */
int avpriv_mpa_decode_header(AVCodecContext *avctx, uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bitrate);
/* fast header check for resync */
static inline int ff_mpa_check_header(uint32_t header){
/* header */
if ((header & 0xffe00000) != 0xffe00000)
return -1;
/* layer check */
if ((header & (3<<17)) == 0)
return -1;
/* bit rate */
if ((header & (0xf<<12)) == 0xf<<12)
return -1;
/* frequency */
if ((header & (3<<10)) == 3<<10)
return -1;
return 0;
}
#endif /* AVCODEC_MPEGAUDIODECHEADER_H */
Jump to Line
Something went wrong with that request. Please try again.