libavcodec/aac_parser.c

   1 /*
   2  * Audio and Video frame extraction
   3  * Copyright (c) 2003 Fabrice Bellard.
   4  * Copyright (c) 2003 Michael Niedermayer.
   5  *
   6  * This file is part of FFmpeg.
   7  *
   8  * FFmpeg is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * FFmpeg is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with FFmpeg; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include "parser.h"
  24 #include "aac_ac3_parser.h"
  25 #include "bitstream.h"
  26 #include "mpeg4audio.h"
  27
  28 #define AAC_HEADER_SIZE 7
  29
  30 static int aac_sync(uint64_t state, AACAC3ParseContext *hdr_info,
  31         int *need_next_header, int *new_frame_start)
  32 {
  33     GetBitContext bits;
  34     int size, rdb, ch, sr;
  35     uint8_t tmp[8];
  36
  37     AV_WB64(tmp, state);
  38     init_get_bits(&bits, tmp+8-AAC_HEADER_SIZE, AAC_HEADER_SIZE * 8);
  39
  40     if(get_bits(&bits, 12) != 0xfff)
  41         return 0;
  42
  43     skip_bits1(&bits);          /* id */
  44     skip_bits(&bits, 2);        /* layer */
  45     skip_bits1(&bits);          /* protection_absent */
  46     skip_bits(&bits, 2);        /* profile_objecttype */
  47     sr = get_bits(&bits, 4);    /* sample_frequency_index */
  48     if(!ff_mpeg4audio_sample_rates[sr])
  49         return 0;
  50     skip_bits1(&bits);          /* private_bit */
  51     ch = get_bits(&bits, 3);    /* channel_configuration */
  52     if(!ff_mpeg4audio_channels[ch])
  53         return 0;
  54     skip_bits1(&bits);          /* original/copy */
  55     skip_bits1(&bits);          /* home */
  56
  57     /* adts_variable_header */
  58     skip_bits1(&bits);          /* copyright_identification_bit */
  59     skip_bits1(&bits);          /* copyright_identification_start */
  60     size = get_bits(&bits, 13); /* aac_frame_length */
  61     if(size < AAC_HEADER_SIZE)
  62         return 0;
  63
  64     skip_bits(&bits, 11);       /* adts_buffer_fullness */
  65     rdb = get_bits(&bits, 2);   /* number_of_raw_data_blocks_in_frame */
  66
  67     hdr_info->channels = ff_mpeg4audio_channels[ch];
  68     hdr_info->sample_rate = ff_mpeg4audio_sample_rates[sr];
  69     hdr_info->samples = (rdb + 1) * 1024;
  70     hdr_info->bit_rate = size * 8 * hdr_info->sample_rate / hdr_info->samples;
  71
  72     *need_next_header = 0;
  73     *new_frame_start  = 1;
  74     return size;
  75 }
  76
  77 static av_cold int aac_parse_init(AVCodecParserContext *s1)
  78 {
  79     AACAC3ParseContext *s = s1->priv_data;
  80     s->header_size = AAC_HEADER_SIZE;
  81     s->sync = aac_sync;
  82     return 0;
  83 }
  84
  85
  86 AVCodecParser aac_parser = {
  87     { CODEC_ID_AAC },
  88     sizeof(AACAC3ParseContext),
  89     aac_parse_init,
  90     ff_aac_ac3_parse,
  91     NULL,
  92 };