latmenc.c
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1 /*
2  * LATM/LOAS muxer
3  * Copyright (c) 2011 Kieran Kunhya <kieran@kunhya.com>
4  *
5  * This file is part of Libav.
6  *
7  * Libav is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * Libav is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with Libav; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 #include "libavcodec/get_bits.h"
23 #include "libavcodec/put_bits.h"
24 #include "libavcodec/avcodec.h"
25 #include "libavcodec/mpeg4audio.h"
26 #include "libavutil/opt.h"
27 #include "avformat.h"
28 
29 typedef struct {
31  int off;
34  int counter;
35  int mod;
36 } LATMContext;
37 
38 static const AVOption options[] = {
39  {"smc-interval", "StreamMuxConfig interval.",
40  offsetof(LATMContext, mod), AV_OPT_TYPE_INT, {.dbl = 0x0014}, 0x0001, 0xffff, AV_OPT_FLAG_ENCODING_PARAM},
41  {NULL},
42 };
43 
44 static const AVClass latm_muxer_class = {
45  .class_name = "LATM/LOAS muxer",
46  .item_name = av_default_item_name,
47  .option = options,
48  .version = LIBAVUTIL_VERSION_INT,
49 };
50 
51 static int latm_decode_extradata(LATMContext *ctx, uint8_t *buf, int size)
52 {
53  GetBitContext gb;
54  MPEG4AudioConfig m4ac;
55 
56  init_get_bits(&gb, buf, size * 8);
57  ctx->off = avpriv_mpeg4audio_get_config(&m4ac, buf, size * 8, 1);
58  if (ctx->off < 0)
59  return ctx->off;
60  skip_bits_long(&gb, ctx->off);
61 
62  /* FIXME: are any formats not allowed in LATM? */
63 
64  if (m4ac.object_type > AOT_SBR && m4ac.object_type != AOT_ALS) {
65  av_log(ctx, AV_LOG_ERROR, "Muxing MPEG-4 AOT %d in LATM is not supported\n", m4ac.object_type);
66  return AVERROR_INVALIDDATA;
67  }
68  ctx->channel_conf = m4ac.chan_config;
69  ctx->object_type = m4ac.object_type;
70 
71  return 0;
72 }
73 
75 {
76  LATMContext *ctx = s->priv_data;
77  AVCodecContext *avctx = s->streams[0]->codec;
78 
79  if (avctx->extradata_size > 0 &&
80  latm_decode_extradata(ctx, avctx->extradata, avctx->extradata_size) < 0)
81  return AVERROR_INVALIDDATA;
82 
83  return 0;
84 }
85 
87 {
88  LATMContext *ctx = s->priv_data;
89  AVCodecContext *avctx = s->streams[0]->codec;
90  GetBitContext gb;
91  int header_size;
92 
93  /* AudioMuxElement */
94  put_bits(bs, 1, !!ctx->counter);
95 
96  if (!ctx->counter) {
97  init_get_bits(&gb, avctx->extradata, avctx->extradata_size * 8);
98 
99  /* StreamMuxConfig */
100  put_bits(bs, 1, 0); /* audioMuxVersion */
101  put_bits(bs, 1, 1); /* allStreamsSameTimeFraming */
102  put_bits(bs, 6, 0); /* numSubFrames */
103  put_bits(bs, 4, 0); /* numProgram */
104  put_bits(bs, 3, 0); /* numLayer */
105 
106  /* AudioSpecificConfig */
107  if (ctx->object_type == AOT_ALS) {
108  header_size = avctx->extradata_size-(ctx->off + 7) >> 3;
109  avpriv_copy_bits(bs, &avctx->extradata[ctx->off], header_size);
110  } else {
111  avpriv_copy_bits(bs, avctx->extradata, ctx->off + 3);
112 
113  if (!ctx->channel_conf) {
114  avpriv_copy_pce_data(bs, &gb);
115  }
116  }
117 
118  put_bits(bs, 3, 0); /* frameLengthType */
119  put_bits(bs, 8, 0xff); /* latmBufferFullness */
120 
121  put_bits(bs, 1, 0); /* otherDataPresent */
122  put_bits(bs, 1, 0); /* crcCheckPresent */
123  }
124 
125  ctx->counter++;
126  ctx->counter %= ctx->mod;
127 
128  return 0;
129 }
130 
132 {
133  AVIOContext *pb = s->pb;
134  PutBitContext bs;
135  int i, len;
136  uint8_t loas_header[] = "\x56\xe0\x00";
137  uint8_t *buf;
138 
139  if (pkt->size > 2 && pkt->data[0] == 0xff && (pkt->data[1] >> 4) == 0xf) {
140  av_log(s, AV_LOG_ERROR, "ADTS header detected - ADTS will not be incorrectly muxed into LATM\n");
141  return AVERROR_INVALIDDATA;
142  }
143 
144  buf = av_malloc(pkt->size+1024);
145  if (!buf)
146  return AVERROR(ENOMEM);
147 
148  init_put_bits(&bs, buf, pkt->size+1024);
149 
150  latm_write_frame_header(s, &bs);
151 
152  /* PayloadLengthInfo() */
153  for (i = 0; i <= pkt->size-255; i+=255)
154  put_bits(&bs, 8, 255);
155 
156  put_bits(&bs, 8, pkt->size-i);
157 
158  /* The LATM payload is written unaligned */
159 
160  /* PayloadMux() */
161  for (i = 0; i < pkt->size; i++)
162  put_bits(&bs, 8, pkt->data[i]);
163 
165  flush_put_bits(&bs);
166 
167  len = put_bits_count(&bs) >> 3;
168 
169  loas_header[1] |= (len >> 8) & 0x1f;
170  loas_header[2] |= len & 0xff;
171 
172  avio_write(pb, loas_header, 3);
173  avio_write(pb, buf, len);
174 
175  av_free(buf);
176 
177  return 0;
178 }
179 
181  .name = "latm",
182  .long_name = NULL_IF_CONFIG_SMALL("LOAS/LATM"),
183  .mime_type = "audio/MP4A-LATM",
184  .extensions = "latm",
185  .priv_data_size = sizeof(LATMContext),
186  .audio_codec = CODEC_ID_AAC,
187  .video_codec = CODEC_ID_NONE,
190  .priv_class = &latm_muxer_class,
191 };