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ffmpeg / libavcodec / aac_parser.c @ 9106a698

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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 "aac_parser.h"
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#include "get_bits.h"
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#include "mpeg4audio.h"
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#define AAC_HEADER_SIZE 7
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int ff_aac_parse_header(GetBitContext *gbc, AACADTSHeaderInfo *hdr)
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{
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    int size, rdb, ch, sr;
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    int aot, crc_abs;
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    if(get_bits(gbc, 12) != 0xfff)
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        return AAC_AC3_PARSE_ERROR_SYNC;
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    skip_bits1(gbc);             /* id */
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    skip_bits(gbc, 2);           /* layer */
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    crc_abs = get_bits1(gbc);    /* protection_absent */
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    aot     = get_bits(gbc, 2);  /* profile_objecttype */
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    sr      = get_bits(gbc, 4);  /* sample_frequency_index */
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    if(!ff_mpeg4audio_sample_rates[sr])
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        return AAC_AC3_PARSE_ERROR_SAMPLE_RATE;
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    skip_bits1(gbc);             /* private_bit */
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    ch      = get_bits(gbc, 3);  /* channel_configuration */
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    if(!ff_mpeg4audio_channels[ch])
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        return AAC_AC3_PARSE_ERROR_CHANNEL_CFG;
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    skip_bits1(gbc);             /* original/copy */
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    skip_bits1(gbc);             /* home */
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    /* adts_variable_header */
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    skip_bits1(gbc);             /* copyright_identification_bit */
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    skip_bits1(gbc);             /* copyright_identification_start */
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    size    = get_bits(gbc, 13); /* aac_frame_length */
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    if(size < AAC_HEADER_SIZE)
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        return AAC_AC3_PARSE_ERROR_FRAME_SIZE;
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    skip_bits(gbc, 11);          /* adts_buffer_fullness */
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    rdb = get_bits(gbc, 2);      /* number_of_raw_data_blocks_in_frame */
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    hdr->object_type    = aot + 1;
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    hdr->chan_config    = ch;
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    hdr->crc_absent     = crc_abs;
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    hdr->num_aac_frames = rdb + 1;
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    hdr->sampling_index = sr;
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    hdr->sample_rate    = ff_mpeg4audio_sample_rates[sr];
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    hdr->samples        = (rdb + 1) * 1024;
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    hdr->bit_rate       = size * 8 * hdr->sample_rate / hdr->samples;
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    return size;
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}
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static int aac_sync(uint64_t state, AACAC3ParseContext *hdr_info,
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        int *need_next_header, int *new_frame_start)
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{
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    GetBitContext bits;
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    AACADTSHeaderInfo hdr;
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    int size;
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    union {
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        uint64_t u64;
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        uint8_t  u8[8];
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    } tmp;
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    tmp.u64 = be2me_64(state);
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    init_get_bits(&bits, tmp.u8+8-AAC_HEADER_SIZE, AAC_HEADER_SIZE * 8);
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    if ((size = ff_aac_parse_header(&bits, &hdr)) < 0)
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        return 0;
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    *need_next_header = 0;
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    *new_frame_start  = 1;
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    hdr_info->sample_rate = hdr.sample_rate;
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    hdr_info->channels    = ff_mpeg4audio_channels[hdr.chan_config];
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    hdr_info->samples     = hdr.samples;
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    hdr_info->bit_rate    = hdr.bit_rate;
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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->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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    ff_parse_close,
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};