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 "aac_parser.h"
  26 #include "get_bits.h"
  27 #include "mpeg4audio.h"
  28
  29 int ff_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(!ff_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    = ff_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 }
  71
  72 static int aac_sync(uint64_t state, AACAC3ParseContext *hdr_info,
  73         int *need_next_header, int *new_frame_start)
  74 {
  75     GetBitContext bits;
  76     AACADTSHeaderInfo hdr;
  77     int size;
  78     union {
  79         uint64_t u64;
  80         uint8_t  u8[8];
  81     } tmp;
  82
  83     tmp.u64 = be2me_64(state);
  84     init_get_bits(&bits, tmp.u8+8-AAC_ADTS_HEADER_SIZE, AAC_ADTS_HEADER_SIZE * 8);
  85
  86     if ((size = ff_aac_parse_header(&bits, &hdr)) < 0)
  87         return 0;
  88     *need_next_header = 0;
  89     *new_frame_start  = 1;
  90     hdr_info->sample_rate = hdr.sample_rate;
  91     hdr_info->channels    = ff_mpeg4audio_channels[hdr.chan_config];
  92     hdr_info->samples     = hdr.samples;
  93     hdr_info->bit_rate    = hdr.bit_rate;
  94     return size;
  95 }
  96
  97 static av_cold int aac_parse_init(AVCodecParserContext *s1)
  98 {
  99     AACAC3ParseContext *s = s1->priv_data;
 100     s->header_size = AAC_ADTS_HEADER_SIZE;
 101     s->sync = aac_sync;
 102     return 0;
 103 }
 104
 105
 106 AVCodecParser aac_parser = {
 107     { CODEC_ID_AAC },
 108     sizeof(AACAC3ParseContext),
 109     aac_parse_init,
 110     ff_aac_ac3_parse,
 111     ff_parse_close,
 112 };