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ffmpeg / libavcodec / mpeg4audio.c @ 9106a698

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/*
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 * MPEG-4 Audio common code
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 * Copyright (c) 2008 Baptiste Coudurier <baptiste.coudurier@free.fr>
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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 "get_bits.h"
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#include "mpeg4audio.h"
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const int ff_mpeg4audio_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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const uint8_t ff_mpeg4audio_channels[8] = {
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    0, 1, 2, 3, 4, 5, 6, 8
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};
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static inline int get_object_type(GetBitContext *gb)
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{
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    int object_type = get_bits(gb, 5);
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    if (object_type == 31)
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        object_type = 32 + get_bits(gb, 6);
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    return object_type;
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}
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static inline int get_sample_rate(GetBitContext *gb, int *index)
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{
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    *index = get_bits(gb, 4);
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    return *index == 0x0f ? get_bits(gb, 24) :
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        ff_mpeg4audio_sample_rates[*index];
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}
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int ff_mpeg4audio_get_config(MPEG4AudioConfig *c, const uint8_t *buf, int buf_size)
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{
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    GetBitContext gb;
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    int specific_config_bitindex;
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    init_get_bits(&gb, buf, buf_size*8);
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    c->object_type = get_object_type(&gb);
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    c->sample_rate = get_sample_rate(&gb, &c->sampling_index);
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    c->chan_config = get_bits(&gb, 4);
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    c->sbr = -1;
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    if (c->object_type == 5) {
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        c->ext_object_type = c->object_type;
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        c->sbr = 1;
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        c->ext_sample_rate = get_sample_rate(&gb, &c->ext_sampling_index);
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        c->object_type = get_object_type(&gb);
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    } else {
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        c->ext_object_type = 0;
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        c->ext_sample_rate = 0;
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    }
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    specific_config_bitindex = get_bits_count(&gb);
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    if (c->ext_object_type != 5) {
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        int bits_left = buf_size*8 - specific_config_bitindex;
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        for (; bits_left > 15; bits_left--) {
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            if (show_bits(&gb, 11) == 0x2b7) { // sync extension
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                get_bits(&gb, 11);
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                c->ext_object_type = get_object_type(&gb);
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                if (c->ext_object_type == 5 && (c->sbr = get_bits1(&gb)) == 1)
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                    c->ext_sample_rate = get_sample_rate(&gb, &c->ext_sampling_index);
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                break;
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            } else
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                get_bits1(&gb); // skip 1 bit
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        }
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    }
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    return specific_config_bitindex;
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}