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