libavformat/adtsenc.c

   1 /*
   2  * ADTS muxer.
   3  * Copyright (c) 2006 Baptiste Coudurier <baptiste.coudurier@smartjog.com>
   4  *                    Mans Rullgard <mans@mansr.com>
   5  *
   6  * This file is part of FFmpeg.
   7  *
   8  * FFmpeg is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * FFmpeg is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with FFmpeg; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #include "libavcodec/bitstream.h"
  24 #include "avformat.h"
  25
  26 #define ADTS_HEADER_SIZE 7
  27
  28 typedef struct {
  29     int write_adts;
  30     int objecttype;
  31     int sample_rate_index;
  32     int channel_conf;
  33 } ADTSContext;
  34
  35 static int decode_extradata(ADTSContext *adts, uint8_t *buf, int size)
  36 {
  37     GetBitContext gb;
  38
  39     init_get_bits(&gb, buf, size * 8);
  40     adts->objecttype = get_bits(&gb, 5) - 1;
  41     adts->sample_rate_index = get_bits(&gb, 4);
  42     adts->channel_conf = get_bits(&gb, 4);
  43
  44     adts->write_adts = 1;
  45
  46     return 0;
  47 }
  48
  49 static int adts_write_header(AVFormatContext *s)
  50 {
  51     ADTSContext *adts = s->priv_data;
  52     AVCodecContext *avc = s->streams[0]->codec;
  53
  54     if(avc->extradata_size > 0)
  55         decode_extradata(adts, avc->extradata, avc->extradata_size);
  56
  57     return 0;
  58 }
  59
  60 static int adts_write_frame_header(AVFormatContext *s, int size)
  61 {
  62     ADTSContext *ctx = s->priv_data;
  63     PutBitContext pb;
  64     uint8_t buf[ADTS_HEADER_SIZE];
  65
  66     init_put_bits(&pb, buf, ADTS_HEADER_SIZE);
  67
  68     /* adts_fixed_header */
  69     put_bits(&pb, 12, 0xfff);   /* syncword */
  70     put_bits(&pb, 1, 0);        /* ID */
  71     put_bits(&pb, 2, 0);        /* layer */
  72     put_bits(&pb, 1, 1);        /* protection_absent */
  73     put_bits(&pb, 2, ctx->objecttype); /* profile_objecttype */
  74     put_bits(&pb, 4, ctx->sample_rate_index);
  75     put_bits(&pb, 1, 0);        /* private_bit */
  76     put_bits(&pb, 3, ctx->channel_conf); /* channel_configuration */
  77     put_bits(&pb, 1, 0);        /* original_copy */
  78     put_bits(&pb, 1, 0);        /* home */
  79
  80     /* adts_variable_header */
  81     put_bits(&pb, 1, 0);        /* copyright_identification_bit */
  82     put_bits(&pb, 1, 0);        /* copyright_identification_start */
  83     put_bits(&pb, 13, ADTS_HEADER_SIZE + size); /* aac_frame_length */
  84     put_bits(&pb, 11, 0x7ff);   /* adts_buffer_fullness */
  85     put_bits(&pb, 2, 0);        /* number_of_raw_data_blocks_in_frame */
  86
  87     flush_put_bits(&pb);
  88     put_buffer(s->pb, buf, ADTS_HEADER_SIZE);
  89
  90     return 0;
  91 }
  92
  93 static int adts_write_packet(AVFormatContext *s, AVPacket *pkt)
  94 {
  95     ADTSContext *adts = s->priv_data;
  96     ByteIOContext *pb = s->pb;
  97
  98     if (!pkt->size)
  99         return 0;
 100     if(adts->write_adts)
 101         adts_write_frame_header(s, pkt->size);
 102     put_buffer(pb, pkt->data, pkt->size);
 103     put_flush_packet(pb);
 104
 105     return 0;
 106 }
 107
 108 AVOutputFormat adts_muxer = {
 109     "adts",
 110     NULL_IF_CONFIG_SMALL("ADTS AAC"),
 111     "audio/aac",
 112     "aac",
 113     sizeof(ADTSContext),
 114     CODEC_ID_AAC,
 115     CODEC_ID_NONE,
 116     adts_write_header,
 117     adts_write_packet,
 118 };