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smoothstreamingenc.c
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1 /*
2  * Live smooth streaming fragmenter
3  * Copyright (c) 2012 Martin Storsjo
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 "config.h"
23 #include <float.h>
24 #if HAVE_UNISTD_H
25 #include <unistd.h>
26 #endif
27 
28 #include "avformat.h"
29 #include "internal.h"
30 #include "os_support.h"
31 #include "avc.h"
32 #include "url.h"
33 #include "isom.h"
34 
35 #include "libavutil/opt.h"
36 #include "libavutil/avstring.h"
37 #include "libavutil/mathematics.h"
38 #include "libavutil/intreadwrite.h"
39 
40 typedef struct {
41  char file[1024];
42  char infofile[1024];
43  int64_t start_time, duration;
44  int n;
45  int64_t start_pos, size;
46 } Fragment;
47 
48 typedef struct {
51  char dirname[1024];
52  uint8_t iobuf[32768];
53  URLContext *out; // Current output stream where all output is written
54  URLContext *out2; // Auxiliary output stream where all output is also written
55  URLContext *tail_out; // The actual main output stream, if we're currently seeked back to write elsewhere
56  int64_t tail_pos, cur_pos, cur_start_pos;
58  const char *stream_type_tag;
59  int nb_fragments, fragments_size, fragment_index;
61 
62  const char *fourcc;
63  char *private_str;
65  int audio_tag;
66 } OutputStream;
67 
68 typedef struct {
69  const AVClass *class; /* Class for private options. */
76  int has_video, has_audio;
79 
80 static int ism_write(void *opaque, uint8_t *buf, int buf_size)
81 {
82  OutputStream *os = opaque;
83  if (os->out)
84  ffurl_write(os->out, buf, buf_size);
85  if (os->out2)
86  ffurl_write(os->out2, buf, buf_size);
87  os->cur_pos += buf_size;
88  if (os->cur_pos >= os->tail_pos)
89  os->tail_pos = os->cur_pos;
90  return buf_size;
91 }
92 
93 static int64_t ism_seek(void *opaque, int64_t offset, int whence)
94 {
95  OutputStream *os = opaque;
96  int i;
97  if (whence != SEEK_SET)
98  return AVERROR(ENOSYS);
99  if (os->tail_out) {
100  if (os->out) {
101  ffurl_close(os->out);
102  }
103  if (os->out2) {
104  ffurl_close(os->out2);
105  }
106  os->out = os->tail_out;
107  os->out2 = NULL;
108  os->tail_out = NULL;
109  }
110  if (offset >= os->cur_start_pos) {
111  if (os->out)
112  ffurl_seek(os->out, offset - os->cur_start_pos, SEEK_SET);
113  os->cur_pos = offset;
114  return offset;
115  }
116  for (i = os->nb_fragments - 1; i >= 0; i--) {
117  Fragment *frag = os->fragments[i];
118  if (offset >= frag->start_pos && offset < frag->start_pos + frag->size) {
119  int ret;
120  AVDictionary *opts = NULL;
121  os->tail_out = os->out;
122  av_dict_set(&opts, "truncate", "0", 0);
123  ret = ffurl_open(&os->out, frag->file, AVIO_FLAG_READ_WRITE, &os->ctx->interrupt_callback, &opts);
124  av_dict_free(&opts);
125  if (ret < 0) {
126  os->out = os->tail_out;
127  os->tail_out = NULL;
128  return ret;
129  }
130  av_dict_set(&opts, "truncate", "0", 0);
132  av_dict_free(&opts);
133  ffurl_seek(os->out, offset - frag->start_pos, SEEK_SET);
134  if (os->out2)
135  ffurl_seek(os->out2, offset - frag->start_pos, SEEK_SET);
136  os->cur_pos = offset;
137  return offset;
138  }
139  }
140  return AVERROR(EIO);
141 }
142 
144 {
145  AVCodecContext *codec = os->ctx->streams[0]->codec;
146  uint8_t *ptr = codec->extradata;
147  int size = codec->extradata_size;
148  int i;
149  if (codec->codec_id == AV_CODEC_ID_H264) {
150  ff_avc_write_annexb_extradata(ptr, &ptr, &size);
151  if (!ptr)
152  ptr = codec->extradata;
153  }
154  if (!ptr)
155  return;
156  os->private_str = av_mallocz(2*size + 1);
157  for (i = 0; i < size; i++)
158  snprintf(&os->private_str[2*i], 3, "%02x", ptr[i]);
159  if (ptr != codec->extradata)
160  av_free(ptr);
161 }
162 
163 static void ism_free(AVFormatContext *s)
164 {
166  int i, j;
167  if (!c->streams)
168  return;
169  for (i = 0; i < s->nb_streams; i++) {
170  OutputStream *os = &c->streams[i];
171  ffurl_close(os->out);
172  ffurl_close(os->out2);
173  ffurl_close(os->tail_out);
174  os->out = os->out2 = os->tail_out = NULL;
175  if (os->ctx && os->ctx_inited)
176  av_write_trailer(os->ctx);
177  if (os->ctx && os->ctx->pb)
178  av_free(os->ctx->pb);
179  if (os->ctx)
181  av_free(os->private_str);
182  for (j = 0; j < os->nb_fragments; j++)
183  av_free(os->fragments[j]);
184  av_free(os->fragments);
185  }
186  av_freep(&c->streams);
187 }
188 
189 static void output_chunk_list(OutputStream *os, AVIOContext *out, int final, int skip, int window_size)
190 {
191  int removed = 0, i, start = 0;
192  if (os->nb_fragments <= 0)
193  return;
194  if (os->fragments[0]->n > 0)
195  removed = 1;
196  if (final)
197  skip = 0;
198  if (window_size)
199  start = FFMAX(os->nb_fragments - skip - window_size, 0);
200  for (i = start; i < os->nb_fragments - skip; i++) {
201  Fragment *frag = os->fragments[i];
202  if (!final || removed)
203  avio_printf(out, "<c t=\"%"PRIu64"\" d=\"%"PRIu64"\" />\n", frag->start_time, frag->duration);
204  else
205  avio_printf(out, "<c n=\"%d\" d=\"%"PRIu64"\" />\n", frag->n, frag->duration);
206  }
207 }
208 
209 static int write_manifest(AVFormatContext *s, int final)
210 {
212  AVIOContext *out;
213  char filename[1024];
214  int ret, i, video_chunks = 0, audio_chunks = 0, video_streams = 0, audio_streams = 0;
215  int64_t duration = 0;
216 
217  snprintf(filename, sizeof(filename), "%s/Manifest", s->filename);
218  ret = avio_open2(&out, filename, AVIO_FLAG_WRITE, &s->interrupt_callback, NULL);
219  if (ret < 0) {
220  av_log(s, AV_LOG_ERROR, "Unable to open %s for writing\n", filename);
221  return ret;
222  }
223  avio_printf(out, "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n");
224  for (i = 0; i < s->nb_streams; i++) {
225  OutputStream *os = &c->streams[i];
226  if (os->nb_fragments > 0) {
227  Fragment *last = os->fragments[os->nb_fragments - 1];
228  duration = last->start_time + last->duration;
229  }
230  if (s->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
231  video_chunks = os->nb_fragments;
232  video_streams++;
233  } else {
234  audio_chunks = os->nb_fragments;
235  audio_streams++;
236  }
237  }
238  if (!final) {
239  duration = 0;
240  video_chunks = audio_chunks = 0;
241  }
242  if (c->window_size) {
243  video_chunks = FFMIN(video_chunks, c->window_size);
244  audio_chunks = FFMIN(audio_chunks, c->window_size);
245  }
246  avio_printf(out, "<SmoothStreamingMedia MajorVersion=\"2\" MinorVersion=\"0\" Duration=\"%"PRIu64"\"", duration);
247  if (!final)
248  avio_printf(out, " IsLive=\"true\" LookAheadFragmentCount=\"%d\" DVRWindowLength=\"0\"", c->lookahead_count);
249  avio_printf(out, ">\n");
250  if (c->has_video) {
251  int last = -1, index = 0;
252  avio_printf(out, "<StreamIndex Type=\"video\" QualityLevels=\"%d\" Chunks=\"%d\" Url=\"QualityLevels({bitrate})/Fragments(video={start time})\">\n", video_streams, video_chunks);
253  for (i = 0; i < s->nb_streams; i++) {
254  OutputStream *os = &c->streams[i];
256  continue;
257  last = i;
258  avio_printf(out, "<QualityLevel Index=\"%d\" Bitrate=\"%d\" FourCC=\"%s\" MaxWidth=\"%d\" MaxHeight=\"%d\" CodecPrivateData=\"%s\" />\n", index, s->streams[i]->codec->bit_rate, os->fourcc, s->streams[i]->codec->width, s->streams[i]->codec->height, os->private_str);
259  index++;
260  }
261  output_chunk_list(&c->streams[last], out, final, c->lookahead_count, c->window_size);
262  avio_printf(out, "</StreamIndex>\n");
263  }
264  if (c->has_audio) {
265  int last = -1, index = 0;
266  avio_printf(out, "<StreamIndex Type=\"audio\" QualityLevels=\"%d\" Chunks=\"%d\" Url=\"QualityLevels({bitrate})/Fragments(audio={start time})\">\n", audio_streams, audio_chunks);
267  for (i = 0; i < s->nb_streams; i++) {
268  OutputStream *os = &c->streams[i];
270  continue;
271  last = i;
272  avio_printf(out, "<QualityLevel Index=\"%d\" Bitrate=\"%d\" FourCC=\"%s\" SamplingRate=\"%d\" Channels=\"%d\" BitsPerSample=\"16\" PacketSize=\"%d\" AudioTag=\"%d\" CodecPrivateData=\"%s\" />\n", index, s->streams[i]->codec->bit_rate, os->fourcc, s->streams[i]->codec->sample_rate, s->streams[i]->codec->channels, os->packet_size, os->audio_tag, os->private_str);
273  index++;
274  }
275  output_chunk_list(&c->streams[last], out, final, c->lookahead_count, c->window_size);
276  avio_printf(out, "</StreamIndex>\n");
277  }
278  avio_printf(out, "</SmoothStreamingMedia>\n");
279  avio_flush(out);
280  avio_close(out);
281  return 0;
282 }
283 
285 {
287  int ret = 0, i;
288  AVOutputFormat *oformat;
289 
290  if (mkdir(s->filename, 0777) < 0) {
291  av_log(s, AV_LOG_ERROR, "mkdir failed\n");
292  ret = AVERROR(errno);
293  goto fail;
294  }
295 
296  oformat = av_guess_format("ismv", NULL, NULL);
297  if (!oformat) {
299  goto fail;
300  }
301 
302  c->streams = av_mallocz(sizeof(*c->streams) * s->nb_streams);
303  if (!c->streams) {
304  ret = AVERROR(ENOMEM);
305  goto fail;
306  }
307 
308  for (i = 0; i < s->nb_streams; i++) {
309  OutputStream *os = &c->streams[i];
310  AVFormatContext *ctx;
311  AVStream *st;
312  AVDictionary *opts = NULL;
313  char buf[10];
314 
315  if (!s->streams[i]->codec->bit_rate) {
316  av_log(s, AV_LOG_ERROR, "No bit rate set for stream %d\n", i);
317  ret = AVERROR(EINVAL);
318  goto fail;
319  }
320  snprintf(os->dirname, sizeof(os->dirname), "%s/QualityLevels(%d)", s->filename, s->streams[i]->codec->bit_rate);
321  if (mkdir(os->dirname, 0777) < 0) {
322  ret = AVERROR(errno);
323  av_log(s, AV_LOG_ERROR, "mkdir failed\n");
324  goto fail;
325  }
326 
327  ctx = avformat_alloc_context();
328  if (!ctx) {
329  ret = AVERROR(ENOMEM);
330  goto fail;
331  }
332  os->ctx = ctx;
333  ctx->oformat = oformat;
335 
336  if (!(st = avformat_new_stream(ctx, NULL))) {
337  ret = AVERROR(ENOMEM);
338  goto fail;
339  }
342 
343  ctx->pb = avio_alloc_context(os->iobuf, sizeof(os->iobuf), AVIO_FLAG_WRITE, os, NULL, ism_write, ism_seek);
344  if (!ctx->pb) {
345  ret = AVERROR(ENOMEM);
346  goto fail;
347  }
348 
349  snprintf(buf, sizeof(buf), "%d", c->lookahead_count);
350  av_dict_set(&opts, "ism_lookahead", buf, 0);
351  av_dict_set(&opts, "movflags", "frag_custom", 0);
352  if ((ret = avformat_write_header(ctx, &opts)) < 0) {
353  goto fail;
354  }
355  os->ctx_inited = 1;
356  avio_flush(ctx->pb);
357  av_dict_free(&opts);
358  s->streams[i]->time_base = st->time_base;
359  if (st->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
360  c->has_video = 1;
361  os->stream_type_tag = "video";
362  if (st->codec->codec_id == AV_CODEC_ID_H264) {
363  os->fourcc = "H264";
364  } else if (st->codec->codec_id == AV_CODEC_ID_VC1) {
365  os->fourcc = "WVC1";
366  } else {
367  av_log(s, AV_LOG_ERROR, "Unsupported video codec\n");
368  ret = AVERROR(EINVAL);
369  goto fail;
370  }
371  } else {
372  c->has_audio = 1;
373  os->stream_type_tag = "audio";
374  if (st->codec->codec_id == AV_CODEC_ID_AAC) {
375  os->fourcc = "AACL";
376  os->audio_tag = 0xff;
377  } else if (st->codec->codec_id == AV_CODEC_ID_WMAPRO) {
378  os->fourcc = "WMAP";
379  os->audio_tag = 0x0162;
380  } else {
381  av_log(s, AV_LOG_ERROR, "Unsupported audio codec\n");
382  ret = AVERROR(EINVAL);
383  goto fail;
384  }
385  os->packet_size = st->codec->block_align ? st->codec->block_align : 4;
386  }
387  get_private_data(os);
388  }
389 
390  if (!c->has_video && c->min_frag_duration <= 0) {
391  av_log(s, AV_LOG_WARNING, "no video stream and no min frag duration set\n");
392  ret = AVERROR(EINVAL);
393  }
394  ret = write_manifest(s, 0);
395 
396 fail:
397  if (ret)
398  ism_free(s);
399  return ret;
400 }
401 
402 static int parse_fragment(AVFormatContext *s, const char *filename, int64_t *start_ts, int64_t *duration, int64_t *moof_size, int64_t size)
403 {
404  AVIOContext *in;
405  int ret;
406  uint32_t len;
407  if ((ret = avio_open2(&in, filename, AVIO_FLAG_READ, &s->interrupt_callback, NULL)) < 0)
408  return ret;
409  ret = AVERROR(EIO);
410  *moof_size = avio_rb32(in);
411  if (*moof_size < 8 || *moof_size > size)
412  goto fail;
413  if (avio_rl32(in) != MKTAG('m','o','o','f'))
414  goto fail;
415  len = avio_rb32(in);
416  if (len > *moof_size)
417  goto fail;
418  if (avio_rl32(in) != MKTAG('m','f','h','d'))
419  goto fail;
420  avio_seek(in, len - 8, SEEK_CUR);
421  avio_rb32(in); /* traf size */
422  if (avio_rl32(in) != MKTAG('t','r','a','f'))
423  goto fail;
424  while (avio_tell(in) < *moof_size) {
425  uint32_t len = avio_rb32(in);
426  uint32_t tag = avio_rl32(in);
427  int64_t end = avio_tell(in) + len - 8;
428  if (len < 8 || len >= *moof_size)
429  goto fail;
430  if (tag == MKTAG('u','u','i','d')) {
431  const uint8_t tfxd[] = {
432  0x6d, 0x1d, 0x9b, 0x05, 0x42, 0xd5, 0x44, 0xe6,
433  0x80, 0xe2, 0x14, 0x1d, 0xaf, 0xf7, 0x57, 0xb2
434  };
435  uint8_t uuid[16];
436  avio_read(in, uuid, 16);
437  if (!memcmp(uuid, tfxd, 16) && len >= 8 + 16 + 4 + 16) {
438  avio_seek(in, 4, SEEK_CUR);
439  *start_ts = avio_rb64(in);
440  *duration = avio_rb64(in);
441  ret = 0;
442  break;
443  }
444  }
445  avio_seek(in, end, SEEK_SET);
446  }
447 fail:
448  avio_close(in);
449  return ret;
450 }
451 
452 static int add_fragment(OutputStream *os, const char *file, const char *infofile, int64_t start_time, int64_t duration, int64_t start_pos, int64_t size)
453 {
454  Fragment *frag;
455  if (os->nb_fragments >= os->fragments_size) {
456  os->fragments_size = (os->fragments_size + 1) * 2;
457  os->fragments = av_realloc(os->fragments, sizeof(*os->fragments)*os->fragments_size);
458  if (!os->fragments)
459  return AVERROR(ENOMEM);
460  }
461  frag = av_mallocz(sizeof(*frag));
462  if (!frag)
463  return AVERROR(ENOMEM);
464  av_strlcpy(frag->file, file, sizeof(frag->file));
465  av_strlcpy(frag->infofile, infofile, sizeof(frag->infofile));
466  frag->start_time = start_time;
467  frag->duration = duration;
468  frag->start_pos = start_pos;
469  frag->size = size;
470  frag->n = os->fragment_index;
471  os->fragments[os->nb_fragments++] = frag;
472  os->fragment_index++;
473  return 0;
474 }
475 
476 static int copy_moof(AVFormatContext *s, const char* infile, const char *outfile, int64_t size)
477 {
478  AVIOContext *in, *out;
479  int ret = 0;
480  if ((ret = avio_open2(&in, infile, AVIO_FLAG_READ, &s->interrupt_callback, NULL)) < 0)
481  return ret;
482  if ((ret = avio_open2(&out, outfile, AVIO_FLAG_WRITE, &s->interrupt_callback, NULL)) < 0) {
483  avio_close(in);
484  return ret;
485  }
486  while (size > 0) {
487  uint8_t buf[8192];
488  int n = FFMIN(size, sizeof(buf));
489  n = avio_read(in, buf, n);
490  if (n <= 0) {
491  ret = AVERROR(EIO);
492  break;
493  }
494  avio_write(out, buf, n);
495  size -= n;
496  }
497  avio_flush(out);
498  avio_close(out);
499  avio_close(in);
500  return ret;
501 }
502 
503 static int ism_flush(AVFormatContext *s, int final)
504 {
506  int i, ret = 0;
507 
508  for (i = 0; i < s->nb_streams; i++) {
509  OutputStream *os = &c->streams[i];
510  char filename[1024], target_filename[1024], header_filename[1024];
511  int64_t start_pos = os->tail_pos, size;
512  int64_t start_ts, duration, moof_size;
513  if (!os->packets_written)
514  continue;
515 
516  snprintf(filename, sizeof(filename), "%s/temp", os->dirname);
517  ret = ffurl_open(&os->out, filename, AVIO_FLAG_WRITE, &s->interrupt_callback, NULL);
518  if (ret < 0)
519  break;
520  os->cur_start_pos = os->tail_pos;
521  av_write_frame(os->ctx, NULL);
522  avio_flush(os->ctx->pb);
523  os->packets_written = 0;
524  if (!os->out || os->tail_out)
525  return AVERROR(EIO);
526 
527  ffurl_close(os->out);
528  os->out = NULL;
529  size = os->tail_pos - start_pos;
530  if ((ret = parse_fragment(s, filename, &start_ts, &duration, &moof_size, size)) < 0)
531  break;
532  snprintf(header_filename, sizeof(header_filename), "%s/FragmentInfo(%s=%"PRIu64")", os->dirname, os->stream_type_tag, start_ts);
533  snprintf(target_filename, sizeof(target_filename), "%s/Fragments(%s=%"PRIu64")", os->dirname, os->stream_type_tag, start_ts);
534  copy_moof(s, filename, header_filename, moof_size);
535  rename(filename, target_filename);
536  add_fragment(os, target_filename, header_filename, start_ts, duration, start_pos, size);
537  }
538 
539  if (c->window_size || (final && c->remove_at_exit)) {
540  for (i = 0; i < s->nb_streams; i++) {
541  OutputStream *os = &c->streams[i];
542  int j;
543  int remove = os->nb_fragments - c->window_size - c->extra_window_size - c->lookahead_count;
544  if (final && c->remove_at_exit)
545  remove = os->nb_fragments;
546  if (remove > 0) {
547  for (j = 0; j < remove; j++) {
548  unlink(os->fragments[j]->file);
549  unlink(os->fragments[j]->infofile);
550  av_free(os->fragments[j]);
551  }
552  os->nb_fragments -= remove;
553  memmove(os->fragments, os->fragments + remove, os->nb_fragments * sizeof(*os->fragments));
554  }
555  if (final && c->remove_at_exit)
556  rmdir(os->dirname);
557  }
558  }
559 
560  if (ret >= 0)
561  ret = write_manifest(s, final);
562  return ret;
563 }
564 
566 {
568  AVStream *st = s->streams[pkt->stream_index];
569  OutputStream *os = &c->streams[pkt->stream_index];
570  int64_t end_dts = (c->nb_fragments + 1LL) * c->min_frag_duration;
571  int ret;
572 
573  if (st->first_dts == AV_NOPTS_VALUE)
574  st->first_dts = pkt->dts;
575 
576  if ((!c->has_video || st->codec->codec_type == AVMEDIA_TYPE_VIDEO) &&
577  av_compare_ts(pkt->dts - st->first_dts, st->time_base,
578  end_dts, AV_TIME_BASE_Q) >= 0 &&
579  pkt->flags & AV_PKT_FLAG_KEY && os->packets_written) {
580 
581  if ((ret = ism_flush(s, 0)) < 0)
582  return ret;
583  c->nb_fragments++;
584  }
585 
586  os->packets_written++;
587  return ff_write_chained(os->ctx, 0, pkt, s);
588 }
589 
591 {
593  ism_flush(s, 1);
594 
595  if (c->remove_at_exit) {
596  char filename[1024];
597  snprintf(filename, sizeof(filename), "%s/Manifest", s->filename);
598  unlink(filename);
599  rmdir(s->filename);
600  }
601 
602  ism_free(s);
603  return 0;
604 }
605 
606 #define OFFSET(x) offsetof(SmoothStreamingContext, x)
607 #define E AV_OPT_FLAG_ENCODING_PARAM
608 static const AVOption options[] = {
609  { "window_size", "number of fragments kept in the manifest", OFFSET(window_size), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, E },
610  { "extra_window_size", "number of fragments kept outside of the manifest before removing from disk", OFFSET(extra_window_size), AV_OPT_TYPE_INT, { .i64 = 5 }, 0, INT_MAX, E },
611  { "lookahead_count", "number of lookahead fragments", OFFSET(lookahead_count), AV_OPT_TYPE_INT, { .i64 = 2 }, 0, INT_MAX, E },
612  { "min_frag_duration", "minimum fragment duration (in microseconds)", OFFSET(min_frag_duration), AV_OPT_TYPE_INT64, { .i64 = 5000000 }, 0, INT_MAX, E },
613  { "remove_at_exit", "remove all fragments when finished", OFFSET(remove_at_exit), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, E },
614  { NULL },
615 };
616 
617 static const AVClass ism_class = {
618  .class_name = "smooth streaming muxer",
619  .item_name = av_default_item_name,
620  .option = options,
621  .version = LIBAVUTIL_VERSION_INT,
622 };
623 
624 
626  .name = "smoothstreaming",
627  .long_name = NULL_IF_CONFIG_SMALL("Smooth Streaming Muxer"),
628  .priv_data_size = sizeof(SmoothStreamingContext),
629  .audio_codec = AV_CODEC_ID_AAC,
630  .video_codec = AV_CODEC_ID_H264,
635  .codec_tag = (const AVCodecTag* const []){ ff_mp4_obj_type, 0 },
636  .priv_class = &ism_class,
637 };