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ffmpeg / libavcodec / aac_parser.c @ be1e2a2b

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/*
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 * Audio and Video frame extraction
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 * Copyright (c) 2003 Fabrice Bellard.
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 * Copyright (c) 2003 Michael Niedermayer.
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 *
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 * This file is part of FFmpeg.
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 *
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 * FFmpeg is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * FFmpeg is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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#include "parser.h"
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#include "aac_ac3_parser.h"
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#include "bitstream.h"
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#define AAC_HEADER_SIZE 7
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static const int aac_sample_rates[16] = {
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    96000, 88200, 64000, 48000, 44100, 32000,
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    24000, 22050, 16000, 12000, 11025, 8000, 7350
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};
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static const int aac_channels[8] = {
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    0, 1, 2, 3, 4, 5, 6, 8
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};
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static int aac_sync(AACAC3ParseContext *hdr_info, AACAC3FrameFlag *flag)
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{
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    GetBitContext bits;
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    int size, rdb, ch, sr;
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    init_get_bits(&bits, hdr_info->inbuf, AAC_HEADER_SIZE * 8);
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    if(get_bits(&bits, 12) != 0xfff)
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        return 0;
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    skip_bits1(&bits);          /* id */
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    skip_bits(&bits, 2);        /* layer */
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    skip_bits1(&bits);          /* protection_absent */
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    skip_bits(&bits, 2);        /* profile_objecttype */
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    sr = get_bits(&bits, 4);    /* sample_frequency_index */
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    if(!aac_sample_rates[sr])
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        return 0;
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    skip_bits1(&bits);          /* private_bit */
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    ch = get_bits(&bits, 3);    /* channel_configuration */
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    if(!aac_channels[ch])
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        return 0;
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    skip_bits1(&bits);          /* original/copy */
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    skip_bits1(&bits);          /* home */
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    /* adts_variable_header */
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    skip_bits1(&bits);          /* copyright_identification_bit */
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    skip_bits1(&bits);          /* copyright_identification_start */
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    size = get_bits(&bits, 13); /* aac_frame_length */
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    if(size < AAC_HEADER_SIZE)
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        return 0;
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    skip_bits(&bits, 11);       /* adts_buffer_fullness */
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    rdb = get_bits(&bits, 2);   /* number_of_raw_data_blocks_in_frame */
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    hdr_info->channels = aac_channels[ch];
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    hdr_info->sample_rate = aac_sample_rates[sr];
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    hdr_info->samples = (rdb + 1) * 1024;
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    hdr_info->bit_rate = size * 8 * hdr_info->sample_rate / hdr_info->samples;
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    *flag = FRAME_COMPLETE;
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    return size;
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}
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static av_cold int aac_parse_init(AVCodecParserContext *s1)
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{
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    AACAC3ParseContext *s = s1->priv_data;
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    s->inbuf_ptr = s->inbuf;
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    s->header_size = AAC_HEADER_SIZE;
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    s->sync = aac_sync;
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    return 0;
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}
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AVCodecParser aac_parser = {
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    { CODEC_ID_AAC },
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    sizeof(AACAC3ParseContext),
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    aac_parse_init,
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    ff_aac_ac3_parse,
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    NULL,
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};