FFmpeg: libavformat/latmenc.c Source File

FFmpeg
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 FFmpeg.
6  *
7  * FFmpeg 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  * FFmpeg 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 FFmpeg; 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 #include "rawenc.h"
29 
30  #define MAX_EXTRADATA_SIZE 1024
31 
32 typedef struct LATMContext {
33   AVClass *av_class;
34   int off;
35   int channel_conf;
36   int object_type;
37   int counter;
38   int mod;
39   uint8_t buffer[0x1fff + MAX_EXTRADATA_SIZE + 1024];
40 } LATMContext;
41 
42  static const AVOption options[] = {
43  {"smc-interval", "StreamMuxConfig interval.",
44  offsetof(LATMContext, mod), AV_OPT_TYPE_INT, {.i64 = 0x0014}, 0x0001, 0xffff, AV_OPT_FLAG_ENCODING_PARAM},
45  {NULL},
46 };
47 
48  static const AVClass latm_muxer_class = {
49  .class_name = "LATM/LOAS muxer",
50  .item_name = av_default_item_name,
51  .option = options,
52  .version = LIBAVUTIL_VERSION_INT,
53 };
54 
55  static int latm_decode_extradata(LATMContext *ctx, uint8_t *buf, int size)
56 {
57  MPEG4AudioConfig m4ac;
58 
59  if (size > MAX_EXTRADATA_SIZE) {
60  av_log(ctx, AV_LOG_ERROR, "Extradata is larger than currently supported.\n");
61  return AVERROR_INVALIDDATA;
62  }
63  ctx->off = avpriv_mpeg4audio_get_config(&m4ac, buf, size * 8, 1);
64  if (ctx->off < 0)
65  return ctx->off;
66 
67  if (ctx->object_type == AOT_ALS && (ctx->off & 7)) {
68  // as long as avpriv_mpeg4audio_get_config works correctly this is impossible
69  av_log(ctx, AV_LOG_ERROR, "BUG: ALS offset is not byte-aligned\n");
70  return AVERROR_INVALIDDATA;
71  }
72  /* FIXME: are any formats not allowed in LATM? */
73 
74  if (m4ac.object_type > AOT_SBR && m4ac.object_type != AOT_ALS) {
75  av_log(ctx, AV_LOG_ERROR, "Muxing MPEG-4 AOT %d in LATM is not supported\n", m4ac.object_type);
76  return AVERROR_INVALIDDATA;
77  }
78  ctx->channel_conf = m4ac.chan_config;
79  ctx->object_type = m4ac.object_type;
80 
81  return 0;
82 }
83 
84  static int latm_write_header(AVFormatContext *s)
85 {
86  LATMContext *ctx = s->priv_data;
87  AVCodecContext *avctx = s->streams[0]->codec;
88 
89  if (avctx->codec_id == AV_CODEC_ID_AAC_LATM)
90  return 0;
91 
92  if (avctx->extradata_size > 0 &&
93  latm_decode_extradata(ctx, avctx->extradata, avctx->extradata_size) < 0)
94  return AVERROR_INVALIDDATA;
95 
96  return 0;
97 }
98 
99  static void latm_write_frame_header(AVFormatContext *s, PutBitContext *bs)
100 {
101  LATMContext *ctx = s->priv_data;
102  AVCodecContext *avctx = s->streams[0]->codec;
103  int header_size;
104 
105  /* AudioMuxElement */
106  put_bits(bs, 1, !!ctx->counter);
107 
108  if (!ctx->counter) {
109  /* StreamMuxConfig */
110  put_bits(bs, 1, 0); /* audioMuxVersion */
111  put_bits(bs, 1, 1); /* allStreamsSameTimeFraming */
112  put_bits(bs, 6, 0); /* numSubFrames */
113  put_bits(bs, 4, 0); /* numProgram */
114  put_bits(bs, 3, 0); /* numLayer */
115 
116  /* AudioSpecificConfig */
117  if (ctx->object_type == AOT_ALS) {
118  header_size = avctx->extradata_size-(ctx->off >> 3);
119  avpriv_copy_bits(bs, &avctx->extradata[ctx->off >> 3], header_size);
120  } else {
121  // + 3 assumes not scalable and dependsOnCoreCoder == 0,
122  // see decode_ga_specific_config in libavcodec/aacdec.c
123  avpriv_copy_bits(bs, avctx->extradata, ctx->off + 3);
124 
125  if (!ctx->channel_conf) {
126  GetBitContext gb;
127  init_get_bits8(&gb, avctx->extradata, avctx->extradata_size);
128  skip_bits_long(&gb, ctx->off + 3);
129  avpriv_copy_pce_data(bs, &gb);
130  }
131  }
132 
133  put_bits(bs, 3, 0); /* frameLengthType */
134  put_bits(bs, 8, 0xff); /* latmBufferFullness */
135 
136  put_bits(bs, 1, 0); /* otherDataPresent */
137  put_bits(bs, 1, 0); /* crcCheckPresent */
138  }
139 
140  ctx->counter++;
141  ctx->counter %= ctx->mod;
142 }
143 
144  static int latm_write_packet(AVFormatContext *s, AVPacket *pkt)
145 {
146  LATMContext *ctx = s->priv_data;
147  AVIOContext *pb = s->pb;
148  PutBitContext bs;
149  int i, len;
150  uint8_t loas_header[] = "\x56\xe0\x00";
151 
152  if (s->streams[0]->codec->codec_id == AV_CODEC_ID_AAC_LATM)
153  return ff_raw_write_packet(s, pkt);
154 
155  if (pkt->size > 2 && pkt->data[0] == 0xff && (pkt->data[1] >> 4) == 0xf) {
156  av_log(s, AV_LOG_ERROR, "ADTS header detected - ADTS will not be incorrectly muxed into LATM\n");
157  return AVERROR_INVALIDDATA;
158  }
159 
160  if (!s->streams[0]->codec->extradata) {
161  if(pkt->size > 2 && pkt->data[0] == 0x56 && (pkt->data[1] >> 4) == 0xe &&
162  (AV_RB16(pkt->data + 1) & 0x1FFF) + 3 == pkt->size)
163  return ff_raw_write_packet(s, pkt);
164  else
165  return AVERROR_INVALIDDATA;
166  }
167 
168  if (pkt->size > 0x1fff)
169  goto too_large;
170 
171  init_put_bits(&bs, ctx->buffer, pkt->size+1024+MAX_EXTRADATA_SIZE);
172 
173  latm_write_frame_header(s, &bs);
174 
175  /* PayloadLengthInfo() */
176  for (i = 0; i <= pkt->size-255; i+=255)
177  put_bits(&bs, 8, 255);
178 
179  put_bits(&bs, 8, pkt->size-i);
180 
181  /* The LATM payload is written unaligned */
182 
183  /* PayloadMux() */
184  if (pkt->size && (pkt->data[0] & 0xe1) == 0x81) {
185  // Convert byte-aligned DSE to non-aligned.
186  // Due to the input format encoding we know that
187  // it is naturally byte-aligned in the input stream,
188  // so there are no padding bits to account for.
189  // To avoid having to add padding bits and rearrange
190  // the whole stream we just remove the byte-align flag.
191  // This allows us to remux our FATE AAC samples into latm
192  // files that are still playable with minimal effort.
193  put_bits(&bs, 8, pkt->data[0] & 0xfe);
194  avpriv_copy_bits(&bs, pkt->data + 1, 8*pkt->size - 8);
195  } else
196  avpriv_copy_bits(&bs, pkt->data, 8*pkt->size);
197 
198  avpriv_align_put_bits(&bs);
199  flush_put_bits(&bs);
200 
201  len = put_bits_count(&bs) >> 3;
202 
203  if (len > 0x1fff)
204  goto too_large;
205 
206  loas_header[1] |= (len >> 8) & 0x1f;
207  loas_header[2] |= len & 0xff;
208 
209  avio_write(pb, loas_header, 3);
210  avio_write(pb, ctx->buffer, len);
211 
212  return 0;
213 
214 too_large:
215  av_log(s, AV_LOG_ERROR, "LATM packet size larger than maximum size 0x1fff\n");
216  return AVERROR_INVALIDDATA;
217 }
218 
219  AVOutputFormat ff_latm_muxer = {
220  .name = "latm",
221  .long_name = NULL_IF_CONFIG_SMALL("LOAS/LATM"),
222  .mime_type = "audio/MP4A-LATM",
223  .extensions = "latm,loas",
224  .priv_data_size = sizeof(LATMContext),
225  .audio_codec = AV_CODEC_ID_AAC,
226  .video_codec = AV_CODEC_ID_NONE,
227  .write_header = latm_write_header,
228  .write_packet = latm_write_packet,
229  .priv_class = &latm_muxer_class,
230  .flags = AVFMT_NOTIMESTAMPS,
231 };
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