ffmpeg/libavcodec/aacadtsdec.c

   1 /*
   2  * Audio and Video frame extraction
   3  * Copyright (c) 2003 Fabrice Bellard
   4  * Copyright (c) 2003 Michael Niedermayer
   5  * Copyright (c) 2009 Alex Converse
   6  *
   7  * This file is part of FFmpeg.
   8  *
   9  * FFmpeg is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License as published by the Free Software Foundation; either
  12  * version 2.1 of the License, or (at your option) any later version.
  13  *
  14  * FFmpeg is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with FFmpeg; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  22  */
  23
  24 #include "aac_ac3_parser.h"
  25 #include "aacadtsdec.h"
  26 #include "get_bits.h"
  27 #include "mpeg4audio.h"
  28
  29 int avpriv_aac_parse_header(GetBitContext *gbc, AACADTSHeaderInfo *hdr)
  30 {
  31     int size, rdb, ch, sr;
  32     int aot, crc_abs;
  33
  34     if (get_bits(gbc, 12) != 0xfff)
  35         return AAC_AC3_PARSE_ERROR_SYNC;
  36
  37     skip_bits1(gbc);             /* id */
  38     skip_bits(gbc, 2);           /* layer */
  39     crc_abs = get_bits1(gbc);    /* protection_absent */
  40     aot     = get_bits(gbc, 2);  /* profile_objecttype */
  41     sr      = get_bits(gbc, 4);  /* sample_frequency_index */
  42     if (!avpriv_mpeg4audio_sample_rates[sr])
  43         return AAC_AC3_PARSE_ERROR_SAMPLE_RATE;
  44     skip_bits1(gbc);             /* private_bit */
  45     ch = get_bits(gbc, 3);       /* channel_configuration */
  46
  47     skip_bits1(gbc);             /* original/copy */
  48     skip_bits1(gbc);             /* home */
  49
  50     /* adts_variable_header */
  51     skip_bits1(gbc);             /* copyright_identification_bit */
  52     skip_bits1(gbc);             /* copyright_identification_start */
  53     size = get_bits(gbc, 13);    /* aac_frame_length */
  54     if (size < AAC_ADTS_HEADER_SIZE)
  55         return AAC_AC3_PARSE_ERROR_FRAME_SIZE;
  56
  57     skip_bits(gbc, 11);          /* adts_buffer_fullness */
  58     rdb = get_bits(gbc, 2);      /* number_of_raw_data_blocks_in_frame */
  59
  60     hdr->object_type    = aot + 1;
  61     hdr->chan_config    = ch;
  62     hdr->crc_absent     = crc_abs;
  63     hdr->num_aac_frames = rdb + 1;
  64     hdr->sampling_index = sr;
  65     hdr->sample_rate    = avpriv_mpeg4audio_sample_rates[sr];
  66     hdr->samples        = (rdb + 1) * 1024;
  67     hdr->bit_rate       = size * 8 * hdr->sample_rate / hdr->samples;
  68
  69     return size;
  70 }