FFmpeg
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
movenchint.c
Go to the documentation of this file.
1 /*
2  * MOV, 3GP, MP4 muxer RTP hinting
3  * Copyright (c) 2010 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 "movenc.h"
23 #include "libavutil/intreadwrite.h"
24 #include "internal.h"
25 #include "rtpenc_chain.h"
26 #include "avio_internal.h"
27 #include "rtp.h"
28 
29 int ff_mov_init_hinting(AVFormatContext *s, int index, int src_index)
30 {
31  MOVMuxContext *mov = s->priv_data;
32  MOVTrack *track = &mov->tracks[index];
33  MOVTrack *src_track = &mov->tracks[src_index];
34  AVStream *src_st = s->streams[src_index];
35  int ret = AVERROR(ENOMEM);
36 
37  track->tag = MKTAG('r','t','p',' ');
38  track->src_track = src_index;
39 
40  track->enc = avcodec_alloc_context3(NULL);
41  if (!track->enc)
42  goto fail;
44  track->enc->codec_tag = track->tag;
45 
46  ret = ff_rtp_chain_mux_open(&track->rtp_ctx, s, src_st, NULL,
47  RTP_MAX_PACKET_SIZE, src_index);
48  if (ret < 0)
49  goto fail;
50 
51  /* Copy the RTP AVStream timebase back to the hint AVStream */
52  track->timescale = track->rtp_ctx->streams[0]->time_base.den;
53 
54  /* Mark the hinted track that packets written to it should be
55  * sent to this track for hinting. */
56  src_track->hint_track = index;
57  return 0;
58 fail:
60  "Unable to initialize hinting of stream %d\n", src_index);
61  av_freep(&track->enc);
62  /* Set a default timescale, to avoid crashes in av_dump_format */
63  track->timescale = 90000;
64  return ret;
65 }
66 
67 /**
68  * Remove the first sample from the sample queue.
69  */
70 static void sample_queue_pop(HintSampleQueue *queue)
71 {
72  if (queue->len <= 0)
73  return;
74  if (queue->samples[0].own_data)
75  av_free(queue->samples[0].data);
76  queue->len--;
77  memmove(queue->samples, queue->samples + 1, sizeof(HintSample)*queue->len);
78 }
79 
80 /**
81  * Empty the sample queue, releasing all memory.
82  */
84 {
85  int i;
86  for (i = 0; i < queue->len; i++)
87  if (queue->samples[i].own_data)
88  av_free(queue->samples[i].data);
89  av_freep(&queue->samples);
90  queue->len = 0;
91  queue->size = 0;
92 }
93 
94 /**
95  * Add a reference to the sample data to the sample queue. The data is
96  * not copied. sample_queue_retain should be called before pkt->data
97  * is reused/freed.
98  */
100  int sample)
101 {
102  /* No need to keep track of smaller samples, since describing them
103  * with immediates is more efficient. */
104  if (size <= 14)
105  return;
106  if (!queue->samples || queue->len >= queue->size) {
107  HintSample *samples;
108  samples = av_realloc_array(queue->samples, queue->size + 10, sizeof(HintSample));
109  if (!samples)
110  return;
111  queue->size += 10;
112  queue->samples = samples;
113  }
114  queue->samples[queue->len].data = data;
115  queue->samples[queue->len].size = size;
116  queue->samples[queue->len].sample_number = sample;
117  queue->samples[queue->len].offset = 0;
118  queue->samples[queue->len].own_data = 0;
119  queue->len++;
120 }
121 
122 /**
123  * Make local copies of all referenced sample data in the queue.
124  */
126 {
127  int i;
128  for (i = 0; i < queue->len; ) {
129  HintSample *sample = &queue->samples[i];
130  if (!sample->own_data) {
131  uint8_t *ptr = av_malloc(sample->size);
132  if (!ptr) {
133  /* Unable to allocate memory for this one, remove it */
134  memmove(queue->samples + i, queue->samples + i + 1,
135  sizeof(HintSample)*(queue->len - i - 1));
136  queue->len--;
137  continue;
138  }
139  memcpy(ptr, sample->data, sample->size);
140  sample->data = ptr;
141  sample->own_data = 1;
142  }
143  i++;
144  }
145 }
146 
147 /**
148  * Find matches of needle[n_pos ->] within haystack. If a sufficiently
149  * large match is found, matching bytes before n_pos are included
150  * in the match, too (within the limits of the arrays).
151  *
152  * @param haystack buffer that may contain parts of needle
153  * @param h_len length of the haystack buffer
154  * @param needle buffer containing source data that have been used to
155  * construct haystack
156  * @param n_pos start position in needle used for looking for matches
157  * @param n_len length of the needle buffer
158  * @param match_h_offset_ptr offset of the first matching byte within haystack
159  * @param match_n_offset_ptr offset of the first matching byte within needle
160  * @param match_len_ptr length of the matched segment
161  * @return 0 if a match was found, < 0 if no match was found
162  */
163 static int match_segments(const uint8_t *haystack, int h_len,
164  const uint8_t *needle, int n_pos, int n_len,
165  int *match_h_offset_ptr, int *match_n_offset_ptr,
166  int *match_len_ptr)
167 {
168  int h_pos;
169  for (h_pos = 0; h_pos < h_len; h_pos++) {
170  int match_len = 0;
171  int match_h_pos, match_n_pos;
172 
173  /* Check how many bytes match at needle[n_pos] and haystack[h_pos] */
174  while (h_pos + match_len < h_len && n_pos + match_len < n_len &&
175  needle[n_pos + match_len] == haystack[h_pos + match_len])
176  match_len++;
177  if (match_len <= 8)
178  continue;
179 
180  /* If a sufficiently large match was found, try to expand
181  * the matched segment backwards. */
182  match_h_pos = h_pos;
183  match_n_pos = n_pos;
184  while (match_n_pos > 0 && match_h_pos > 0 &&
185  needle[match_n_pos - 1] == haystack[match_h_pos - 1]) {
186  match_n_pos--;
187  match_h_pos--;
188  match_len++;
189  }
190  if (match_len <= 14)
191  continue;
192  *match_h_offset_ptr = match_h_pos;
193  *match_n_offset_ptr = match_n_pos;
194  *match_len_ptr = match_len;
195  return 0;
196  }
197  return -1;
198 }
199 
200 /**
201  * Look for segments in samples in the sample queue matching the data
202  * in ptr. Samples not matching are removed from the queue. If a match
203  * is found, the next time it will look for matches starting from the
204  * end of the previous matched segment.
205  *
206  * @param data data to find matches for in the sample queue
207  * @param len length of the data buffer
208  * @param queue samples used for looking for matching segments
209  * @param pos the offset in data of the matched segment
210  * @param match_sample the number of the sample that contained the match
211  * @param match_offset the offset of the matched segment within the sample
212  * @param match_len the length of the matched segment
213  * @return 0 if a match was found, < 0 if no match was found
214  */
215 static int find_sample_match(const uint8_t *data, int len,
216  HintSampleQueue *queue, int *pos,
217  int *match_sample, int *match_offset,
218  int *match_len)
219 {
220  while (queue->len > 0) {
221  HintSample *sample = &queue->samples[0];
222  /* If looking for matches in a new sample, skip the first 5 bytes,
223  * since they often may be modified/removed in the output packet. */
224  if (sample->offset == 0 && sample->size > 5)
225  sample->offset = 5;
226 
227  if (match_segments(data, len, sample->data, sample->offset,
228  sample->size, pos, match_offset, match_len) == 0) {
229  *match_sample = sample->sample_number;
230  /* Next time, look for matches at this offset, with a little
231  * margin to this match. */
232  sample->offset = *match_offset + *match_len + 5;
233  if (sample->offset + 10 >= sample->size)
234  sample_queue_pop(queue); /* Not enough useful data left */
235  return 0;
236  }
237 
238  if (sample->offset < 10 && sample->size > 20) {
239  /* No match found from the start of the sample,
240  * try from the middle of the sample instead. */
241  sample->offset = sample->size/2;
242  } else {
243  /* No match for this sample, remove it */
244  sample_queue_pop(queue);
245  }
246  }
247  return -1;
248 }
249 
250 static void output_immediate(const uint8_t *data, int size,
251  AVIOContext *out, int *entries)
252 {
253  while (size > 0) {
254  int len = size;
255  if (len > 14)
256  len = 14;
257  avio_w8(out, 1); /* immediate constructor */
258  avio_w8(out, len); /* amount of valid data */
259  avio_write(out, data, len);
260  data += len;
261  size -= len;
262 
263  for (; len < 14; len++)
264  avio_w8(out, 0);
265 
266  (*entries)++;
267  }
268 }
269 
270 static void output_match(AVIOContext *out, int match_sample,
271  int match_offset, int match_len, int *entries)
272 {
273  avio_w8(out, 2); /* sample constructor */
274  avio_w8(out, 0); /* track reference */
275  avio_wb16(out, match_len);
276  avio_wb32(out, match_sample);
277  avio_wb32(out, match_offset);
278  avio_wb16(out, 1); /* bytes per block */
279  avio_wb16(out, 1); /* samples per block */
280  (*entries)++;
281 }
282 
283 static void describe_payload(const uint8_t *data, int size,
284  AVIOContext *out, int *entries,
285  HintSampleQueue *queue)
286 {
287  /* Describe the payload using different constructors */
288  while (size > 0) {
289  int match_sample, match_offset, match_len, pos;
290  if (find_sample_match(data, size, queue, &pos, &match_sample,
291  &match_offset, &match_len) < 0)
292  break;
293  output_immediate(data, pos, out, entries);
294  data += pos;
295  size -= pos;
296  output_match(out, match_sample, match_offset, match_len, entries);
297  data += match_len;
298  size -= match_len;
299  }
300  output_immediate(data, size, out, entries);
301 }
302 
303 /**
304  * Write an RTP hint (that may contain one or more RTP packets)
305  * for the packets in data. data contains one or more packets with a
306  * BE32 size header.
307  *
308  * @param out buffer where the hints are written
309  * @param data buffer containing RTP packets
310  * @param size the size of the data buffer
311  * @param trk the MOVTrack for the hint track
312  * @param dts pointer where the timestamp for the written RTP hint is stored
313  * @return the number of RTP packets in the written hint
314  */
316  int size, MOVTrack *trk, int64_t *dts)
317 {
318  int64_t curpos;
319  int64_t count_pos, entries_pos;
320  int count = 0, entries;
321 
322  count_pos = avio_tell(out);
323  /* RTPsample header */
324  avio_wb16(out, 0); /* packet count */
325  avio_wb16(out, 0); /* reserved */
326 
327  while (size > 4) {
328  uint32_t packet_len = AV_RB32(data);
329  uint16_t seq;
330  uint32_t ts;
331  int32_t ts_diff;
332 
333  data += 4;
334  size -= 4;
335  if (packet_len > size || packet_len <= 12)
336  break;
337  if (RTP_PT_IS_RTCP(data[1])) {
338  /* RTCP packet, just skip */
339  data += packet_len;
340  size -= packet_len;
341  continue;
342  }
343 
344  if (packet_len > trk->max_packet_size)
345  trk->max_packet_size = packet_len;
346 
347  seq = AV_RB16(&data[2]);
348  ts = AV_RB32(&data[4]);
349 
350  if (trk->prev_rtp_ts == 0)
351  trk->prev_rtp_ts = ts;
352  /* Unwrap the 32-bit RTP timestamp that wraps around often
353  * into a not (as often) wrapping 64-bit timestamp. */
354  ts_diff = ts - trk->prev_rtp_ts;
355  if (ts_diff > 0) {
356  trk->cur_rtp_ts_unwrapped += ts_diff;
357  trk->prev_rtp_ts = ts;
358  ts_diff = 0;
359  }
360  if (*dts == AV_NOPTS_VALUE)
361  *dts = trk->cur_rtp_ts_unwrapped;
362 
363  count++;
364  /* RTPpacket header */
365  avio_wb32(out, 0); /* relative_time */
366  avio_write(out, data, 2); /* RTP header */
367  avio_wb16(out, seq); /* RTPsequenceseed */
368  avio_wb16(out, ts_diff ? 4 : 0); /* reserved + flags (extra_flag) */
369  entries_pos = avio_tell(out);
370  avio_wb16(out, 0); /* entry count */
371  if (ts_diff) { /* if extra_flag is set */
372  avio_wb32(out, 16); /* extra_information_length */
373  avio_wb32(out, 12); /* rtpoffsetTLV box */
374  avio_write(out, "rtpo", 4);
375  avio_wb32(out, ts_diff);
376  }
377 
378  data += 12;
379  size -= 12;
380  packet_len -= 12;
381 
382  entries = 0;
383  /* Write one or more constructors describing the payload data */
384  describe_payload(data, packet_len, out, &entries, &trk->sample_queue);
385  data += packet_len;
386  size -= packet_len;
387 
388  curpos = avio_tell(out);
389  avio_seek(out, entries_pos, SEEK_SET);
390  avio_wb16(out, entries);
391  avio_seek(out, curpos, SEEK_SET);
392  }
393 
394  curpos = avio_tell(out);
395  avio_seek(out, count_pos, SEEK_SET);
396  avio_wb16(out, count);
397  avio_seek(out, curpos, SEEK_SET);
398  return count;
399 }
400 
402  int track_index, int sample,
403  uint8_t *sample_data, int sample_size)
404 {
405  MOVMuxContext *mov = s->priv_data;
406  MOVTrack *trk = &mov->tracks[track_index];
407  AVFormatContext *rtp_ctx = trk->rtp_ctx;
408  uint8_t *buf = NULL;
409  int size;
410  AVIOContext *hintbuf = NULL;
411  AVPacket hint_pkt;
412  int ret = 0, count;
413 
414  if (!rtp_ctx)
415  return AVERROR(ENOENT);
416  if (!rtp_ctx->pb)
417  return AVERROR(ENOMEM);
418 
419  if (sample_data)
420  sample_queue_push(&trk->sample_queue, sample_data, sample_size, sample);
421  else
422  sample_queue_push(&trk->sample_queue, pkt->data, pkt->size, sample);
423 
424  /* Feed the packet to the RTP muxer */
425  ff_write_chained(rtp_ctx, 0, pkt, s, 0);
426 
427  /* Fetch the output from the RTP muxer, open a new output buffer
428  * for next time. */
429  size = avio_close_dyn_buf(rtp_ctx->pb, &buf);
430  if ((ret = ffio_open_dyn_packet_buf(&rtp_ctx->pb,
431  RTP_MAX_PACKET_SIZE)) < 0)
432  goto done;
433 
434  if (size <= 0)
435  goto done;
436 
437  /* Open a buffer for writing the hint */
438  if ((ret = avio_open_dyn_buf(&hintbuf)) < 0)
439  goto done;
440  av_init_packet(&hint_pkt);
441  count = write_hint_packets(hintbuf, buf, size, trk, &hint_pkt.dts);
442  av_freep(&buf);
443 
444  /* Write the hint data into the hint track */
445  hint_pkt.size = size = avio_close_dyn_buf(hintbuf, &buf);
446  hint_pkt.data = buf;
447  hint_pkt.pts = hint_pkt.dts;
448  hint_pkt.stream_index = track_index;
449  if (pkt->flags & AV_PKT_FLAG_KEY)
450  hint_pkt.flags |= AV_PKT_FLAG_KEY;
451  if (count > 0)
452  ff_mov_write_packet(s, &hint_pkt);
453 done:
454  av_free(buf);
456  return ret;
457 }
458 
460 {
461  AVFormatContext *rtp_ctx = track->rtp_ctx;
462  uint8_t *ptr;
463 
464  av_freep(&track->enc);
466  if (!rtp_ctx)
467  return;
468  if (rtp_ctx->pb) {
469  av_write_trailer(rtp_ctx);
470  avio_close_dyn_buf(rtp_ctx->pb, &ptr);
471  av_free(ptr);
472  }
473  avformat_free_context(rtp_ctx);
474 }