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Member "ffmpeg-3.4.2/libavcodec/aacadtsdec.c" (29 Mar 2016, 2594 Bytes) of package /linux/misc/ffmpeg-3.4.2.tar.xz:


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    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 }