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ffmpeg / libavformat / adtsenc.c @ 470bce2b

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/*
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 * ADTS muxer.
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 * Copyright (c) 2006 Baptiste Coudurier <baptiste.coudurier@smartjog.com>
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 *                    Mans Rullgard <mans@mansr.com>
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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 "libavcodec/bitstream.h"
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#include "avformat.h"
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#define ADTS_HEADER_SIZE 7
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typedef struct {
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    int write_adts;
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    int objecttype;
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    int sample_rate_index;
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    int channel_conf;
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} ADTSContext;
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static int decode_extradata(ADTSContext *adts, uint8_t *buf, int size)
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{
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    GetBitContext gb;
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    init_get_bits(&gb, buf, size * 8);
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    adts->objecttype = get_bits(&gb, 5) - 1;
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    adts->sample_rate_index = get_bits(&gb, 4);
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    adts->channel_conf = get_bits(&gb, 4);
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    adts->write_adts = 1;
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    return 0;
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}
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static int adts_write_header(AVFormatContext *s)
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{
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    ADTSContext *adts = s->priv_data;
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    AVCodecContext *avc = s->streams[0]->codec;
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    if(avc->extradata_size > 0)
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        decode_extradata(adts, avc->extradata, avc->extradata_size);
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    return 0;
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}
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static int adts_write_frame_header(AVFormatContext *s, int size)
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{
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    ADTSContext *ctx = s->priv_data;
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    PutBitContext pb;
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    uint8_t buf[ADTS_HEADER_SIZE];
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    init_put_bits(&pb, buf, ADTS_HEADER_SIZE);
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    /* adts_fixed_header */
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    put_bits(&pb, 12, 0xfff);   /* syncword */
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    put_bits(&pb, 1, 0);        /* ID */
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    put_bits(&pb, 2, 0);        /* layer */
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    put_bits(&pb, 1, 1);        /* protection_absent */
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    put_bits(&pb, 2, ctx->objecttype); /* profile_objecttype */
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    put_bits(&pb, 4, ctx->sample_rate_index);
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    put_bits(&pb, 1, 0);        /* private_bit */
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    put_bits(&pb, 3, ctx->channel_conf); /* channel_configuration */
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    put_bits(&pb, 1, 0);        /* original_copy */
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    put_bits(&pb, 1, 0);        /* home */
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    /* adts_variable_header */
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    put_bits(&pb, 1, 0);        /* copyright_identification_bit */
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    put_bits(&pb, 1, 0);        /* copyright_identification_start */
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    put_bits(&pb, 13, ADTS_HEADER_SIZE + size); /* aac_frame_length */
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    put_bits(&pb, 11, 0x7ff);   /* adts_buffer_fullness */
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    put_bits(&pb, 2, 0);        /* number_of_raw_data_blocks_in_frame */
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    flush_put_bits(&pb);
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    put_buffer(s->pb, buf, ADTS_HEADER_SIZE);
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    return 0;
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}
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static int adts_write_packet(AVFormatContext *s, AVPacket *pkt)
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{
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    ADTSContext *adts = s->priv_data;
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    ByteIOContext *pb = s->pb;
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    if (!pkt->size)
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        return 0;
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    if(adts->write_adts)
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        adts_write_frame_header(s, pkt->size);
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    put_buffer(pb, pkt->data, pkt->size);
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    put_flush_packet(pb);
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    return 0;
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}
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AVOutputFormat adts_muxer = {
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    "adts",
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    NULL_IF_CONFIG_SMALL("ADTS AAC"),
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    "audio/aac",
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    "aac",
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    sizeof(ADTSContext),
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    CODEC_ID_AAC,
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    CODEC_ID_NONE,
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    adts_write_header,
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    adts_write_packet,
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};