ffmpeg/libavcodec/mpegaudiodecheader.h

   1 /*
   2  * MPEG Audio header decoder
   3  * Copyright (c) 2001, 2002 Fabrice Bellard
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 /**
  23  * @file
  24  * MPEG Audio header decoder.
  25  */
  26
  27 #ifndef AVCODEC_MPEGAUDIODECHEADER_H
  28 #define AVCODEC_MPEGAUDIODECHEADER_H
  29
  30 #include "avcodec.h"
  31
  32 #define MP3_MASK 0xFFFE0CCF
  33
  34 #define MPA_DECODE_HEADER \
  35     int frame_size; \
  36     int error_protection; \
  37     int layer; \
  38     int sample_rate; \
  39     int sample_rate_index; /* between 0 and 8 */ \
  40     int bit_rate; \
  41     int nb_channels; \
  42     int mode; \
  43     int mode_ext; \
  44     int lsf;
  45
  46 typedef struct MPADecodeHeader {
  47   MPA_DECODE_HEADER
  48 } MPADecodeHeader;
  49
  50 /* header decoding. MUST check the header before because no
  51    consistency check is done there. Return 1 if free format found and
  52    that the frame size must be computed externally */
  53 int avpriv_mpegaudio_decode_header(MPADecodeHeader *s, uint32_t header);
  54
  55 /* useful helper to get mpeg audio stream infos. Return -1 if error in
  56    header, otherwise the coded frame size in bytes */
  57 int avpriv_mpa_decode_header(AVCodecContext *avctx, uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bitrate);
  58
  59 int avpriv_mpa_decode_header2(uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bitrate, enum AVCodecID *codec_id);
  60
  61 /* fast header check for resync */
  62 static inline int ff_mpa_check_header(uint32_t header){
  63     /* header */
  64     if ((header & 0xffe00000) != 0xffe00000)
  65         return -1;
  66     /* layer check */
  67     if ((header & (3<<17)) == 0)
  68         return -1;
  69     /* bit rate */
  70     if ((header & (0xf<<12)) == 0xf<<12)
  71         return -1;
  72     /* frequency */
  73     if ((header & (3<<10)) == 3<<10)
  74         return -1;
  75     return 0;
  76 }
  77
  78 #endif /* AVCODEC_MPEGAUDIODECHEADER_H */