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 "bitstream.h"
  27 #include "mpeg4audio.h"
  28
  29 #define AAC_HEADER_SIZE 7
  30
  31 int ff_aac_parse_header(GetBitContext *gbc, AACADTSHeaderInfo *hdr)
  32 {
  33     int size, rdb, ch, sr;
  34     int aot, crc_abs;
  35
  36     if(get_bits(gbc, 12) != 0xfff)
  37         return AAC_AC3_PARSE_ERROR_SYNC;
  38
  39     skip_bits1(gbc);             /* id */
  40     skip_bits(gbc, 2);           /* layer */
  41     crc_abs = get_bits1(gbc);    /* protection_absent */
  42     aot     = get_bits(gbc, 2);  /* profile_objecttype */
  43     sr      = get_bits(gbc, 4);  /* sample_frequency_index */
  44     if(!ff_mpeg4audio_sample_rates[sr])
  45         return AAC_AC3_PARSE_ERROR_SAMPLE_RATE;
  46     skip_bits1(gbc);             /* private_bit */
  47     ch      = get_bits(gbc, 3);  /* channel_configuration */
  48
  49     if(!ff_mpeg4audio_channels[ch])
  50         return AAC_AC3_PARSE_ERROR_CHANNEL_CFG;
  51
  52     skip_bits1(gbc);             /* original/copy */
  53     skip_bits1(gbc);             /* home */
  54
  55     /* adts_variable_header */
  56     skip_bits1(gbc);             /* copyright_identification_bit */
  57     skip_bits1(gbc);             /* copyright_identification_start */
  58     size    = get_bits(gbc, 13); /* aac_frame_length */
  59     if(size < AAC_HEADER_SIZE)
  60         return AAC_AC3_PARSE_ERROR_FRAME_SIZE;
  61
  62     skip_bits(gbc, 11);          /* adts_buffer_fullness */
  63     rdb = get_bits(gbc, 2);      /* number_of_raw_data_blocks_in_frame */
  64
  65     hdr->object_type    = aot + 1;
  66     hdr->chan_config    = ch;
  67     hdr->crc_absent     = crc_abs;
  68     hdr->num_aac_frames = rdb + 1;
  69     hdr->sampling_index = sr;
  70     hdr->sample_rate    = ff_mpeg4audio_sample_rates[sr];
  71     hdr->samples        = (rdb + 1) * 1024;
  72     hdr->bit_rate       = size * 8 * hdr->sample_rate / hdr->samples;
  73
  74     return size;
  75 }
  76
  77 static int aac_sync(uint64_t state, AACAC3ParseContext *hdr_info,
  78         int *need_next_header, int *new_frame_start)
  79 {
  80     GetBitContext bits;
  81     AACADTSHeaderInfo hdr;
  82     int size;
  83     union {
  84         uint64_t u64;
  85         uint8_t  u8[8];
  86     } tmp;
  87
  88     tmp.u64 = be2me_64(state);
  89     init_get_bits(&bits, tmp.u8+8-AAC_HEADER_SIZE, AAC_HEADER_SIZE * 8);
  90
  91     if ((size = ff_aac_parse_header(&bits, &hdr)) < 0)
  92         return 0;
  93     *need_next_header = 0;
  94     *new_frame_start  = 1;
  95     hdr_info->sample_rate = hdr.sample_rate;
  96     hdr_info->channels    = ff_mpeg4audio_channels[hdr.chan_config];
  97     hdr_info->samples     = hdr.samples;
  98     hdr_info->bit_rate    = hdr.bit_rate;
  99     return size;
 100 }
 101
 102 static av_cold int aac_parse_init(AVCodecParserContext *s1)
 103 {
 104     AACAC3ParseContext *s = s1->priv_data;
 105     s->header_size = AAC_HEADER_SIZE;
 106     s->sync = aac_sync;
 107     return 0;
 108 }
 109
 110
 111 AVCodecParser aac_parser = {
 112     { CODEC_ID_AAC },
 113     sizeof(AACAC3ParseContext),
 114     aac_parse_init,
 115     ff_aac_ac3_parse,
 116     ff_parse_close,
 117 };