FFmpeg
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ffmdec.c
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1 /*
2  * FFM (ffserver live feed) demuxer
3  * Copyright (c) 2001 Fabrice Bellard
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 <stdint.h>
23 
24 #include "libavutil/intreadwrite.h"
25 #include "libavutil/intfloat.h"
26 #include "libavutil/opt.h"
27 #include "libavutil/avassert.h"
28 #include "libavutil/avstring.h"
29 #include "avformat.h"
30 #include "internal.h"
31 #include "ffm.h"
32 #include "avio_internal.h"
33 
35 {
36  FFMContext *ffm = s->priv_data;
37  int64_t pos, avail_size;
38  int len;
39 
40  len = ffm->packet_end - ffm->packet_ptr;
41  if (size <= len)
42  return 1;
43  pos = avio_tell(s->pb);
44  if (!ffm->write_index) {
45  if (pos == ffm->file_size)
46  return AVERROR_EOF;
47  avail_size = ffm->file_size - pos;
48  } else {
49  if (pos == ffm->write_index) {
50  /* exactly at the end of stream */
51  return AVERROR(EAGAIN);
52  } else if (pos < ffm->write_index) {
53  avail_size = ffm->write_index - pos;
54  } else {
55  avail_size = (ffm->file_size - pos) + (ffm->write_index - FFM_PACKET_SIZE);
56  }
57  }
58  avail_size = (avail_size / ffm->packet_size) * (ffm->packet_size - FFM_HEADER_SIZE) + len;
59  if (size <= avail_size)
60  return 1;
61  else
62  return AVERROR(EAGAIN);
63 }
64 
65 static int ffm_resync(AVFormatContext *s, int state)
66 {
67  av_log(s, AV_LOG_ERROR, "resyncing\n");
68  while (state != PACKET_ID) {
69  if (avio_feof(s->pb)) {
70  av_log(s, AV_LOG_ERROR, "cannot find FFM syncword\n");
71  return -1;
72  }
73  state = (state << 8) | avio_r8(s->pb);
74  }
75  return 0;
76 }
77 
78 /* first is true if we read the frame header */
80  uint8_t *buf, int size, int header)
81 {
82  FFMContext *ffm = s->priv_data;
83  AVIOContext *pb = s->pb;
84  int len, fill_size, size1, frame_offset, id;
85  int64_t last_pos = -1;
86 
87  size1 = size;
88  while (size > 0) {
89  redo:
90  len = ffm->packet_end - ffm->packet_ptr;
91  if (len < 0)
92  return -1;
93  if (len > size)
94  len = size;
95  if (len == 0) {
96  if (avio_tell(pb) == ffm->file_size)
97  avio_seek(pb, ffm->packet_size, SEEK_SET);
98  retry_read:
99  if (pb->buffer_size != ffm->packet_size) {
100  int64_t tell = avio_tell(pb);
101  ffio_set_buf_size(pb, ffm->packet_size);
102  avio_seek(pb, tell, SEEK_SET);
103  }
104  id = avio_rb16(pb); /* PACKET_ID */
105  if (id != PACKET_ID) {
106  if (ffm_resync(s, id) < 0)
107  return -1;
108  last_pos = avio_tell(pb);
109  }
110  fill_size = avio_rb16(pb);
111  ffm->dts = avio_rb64(pb);
112  frame_offset = avio_rb16(pb);
113  avio_read(pb, ffm->packet, ffm->packet_size - FFM_HEADER_SIZE);
114  ffm->packet_end = ffm->packet + (ffm->packet_size - FFM_HEADER_SIZE - fill_size);
115  if (ffm->packet_end < ffm->packet || frame_offset < 0)
116  return -1;
117  /* if first packet or resynchronization packet, we must
118  handle it specifically */
119  if (ffm->first_packet || (frame_offset & 0x8000)) {
120  if (!frame_offset) {
121  /* This packet has no frame headers in it */
122  if (avio_tell(pb) >= ffm->packet_size * 3LL) {
123  int64_t seekback = FFMIN(ffm->packet_size * 2LL, avio_tell(pb) - last_pos);
124  seekback = FFMAX(seekback, 0);
125  avio_seek(pb, -seekback, SEEK_CUR);
126  goto retry_read;
127  }
128  /* This is bad, we cannot find a valid frame header */
129  return 0;
130  }
131  ffm->first_packet = 0;
132  if ((frame_offset & 0x7fff) < FFM_HEADER_SIZE)
133  return -1;
134  ffm->packet_ptr = ffm->packet + (frame_offset & 0x7fff) - FFM_HEADER_SIZE;
135  if (!header)
136  break;
137  } else {
138  ffm->packet_ptr = ffm->packet;
139  }
140  goto redo;
141  }
142  memcpy(buf, ffm->packet_ptr, len);
143  buf += len;
144  ffm->packet_ptr += len;
145  size -= len;
146  header = 0;
147  }
148  return size1 - size;
149 }
150 
151 /* ensure that acutal seeking happens between FFM_PACKET_SIZE
152  and file_size - FFM_PACKET_SIZE */
153 static int64_t ffm_seek1(AVFormatContext *s, int64_t pos1)
154 {
155  FFMContext *ffm = s->priv_data;
156  AVIOContext *pb = s->pb;
157  int64_t pos;
158 
159  pos = FFMIN(pos1, ffm->file_size - FFM_PACKET_SIZE);
160  pos = FFMAX(pos, FFM_PACKET_SIZE);
161  av_dlog(s, "seek to %"PRIx64" -> %"PRIx64"\n", pos1, pos);
162  return avio_seek(pb, pos, SEEK_SET);
163 }
164 
165 static int64_t get_dts(AVFormatContext *s, int64_t pos)
166 {
167  AVIOContext *pb = s->pb;
168  int64_t dts;
169 
170  ffm_seek1(s, pos);
171  avio_skip(pb, 4);
172  dts = avio_rb64(pb);
173  av_dlog(s, "dts=%0.6f\n", dts / 1000000.0);
174  return dts;
175 }
176 
178 {
179  FFMContext *ffm = s->priv_data;
180  AVIOContext *pb = s->pb;
181  int64_t pts;
182  //int64_t orig_write_index = ffm->write_index;
183  int64_t pos_min, pos_max;
184  int64_t pts_start;
185  int64_t ptr = avio_tell(pb);
186 
187 
188  pos_min = 0;
189  pos_max = ffm->file_size - 2 * FFM_PACKET_SIZE;
190 
191  pts_start = get_dts(s, pos_min);
192 
193  pts = get_dts(s, pos_max);
194 
195  if (pts - 100000 > pts_start)
196  goto end;
197 
199 
200  pts_start = get_dts(s, pos_min);
201 
202  pts = get_dts(s, pos_max);
203 
204  if (pts - 100000 <= pts_start) {
205  while (1) {
206  int64_t newpos;
207  int64_t newpts;
208 
209  newpos = ((pos_max + pos_min) / (2 * FFM_PACKET_SIZE)) * FFM_PACKET_SIZE;
210 
211  if (newpos == pos_min)
212  break;
213 
214  newpts = get_dts(s, newpos);
215 
216  if (newpts - 100000 <= pts) {
217  pos_max = newpos;
218  pts = newpts;
219  } else {
220  pos_min = newpos;
221  }
222  }
223  ffm->write_index += pos_max;
224  }
225 
226  end:
227  avio_seek(pb, ptr, SEEK_SET);
228 }
229 
230 
232 {
233  int i;
234 
235  for (i = 0; i < s->nb_streams; i++)
236  av_freep(&s->streams[i]->codec->rc_eq);
237 
238  return 0;
239 }
240 
241 static int ffm_append_recommended_configuration(AVStream *st, char **conf)
242 {
243  int ret;
244  size_t newsize;
245  av_assert0(conf && st);
246  if (!*conf)
247  return 0;
250  *conf = 0;
251  return 0;
252  }
253  newsize = strlen(*conf) + strlen(st->recommended_encoder_configuration) + 2;
254  if ((ret = av_reallocp(&st->recommended_encoder_configuration, newsize)) < 0)
255  return ret;
257  av_strlcat(st->recommended_encoder_configuration, *conf, newsize);
258  av_freep(conf);
259  return 0;
260 }
261 
263 {
264  FFMContext *ffm = s->priv_data;
265  AVStream *st;
266  AVIOContext *pb = s->pb;
267  AVCodecContext *codec;
268  int ret;
269  int f_main = 0, f_cprv = -1, f_stvi = -1, f_stau = -1;
270  AVCodec *enc;
271  char *buffer;
272 
273  ffm->packet_size = avio_rb32(pb);
274  if (ffm->packet_size != FFM_PACKET_SIZE) {
275  av_log(s, AV_LOG_ERROR, "Invalid packet size %d, expected size was %d\n",
277  ret = AVERROR_INVALIDDATA;
278  goto fail;
279  }
280 
281  ffm->write_index = avio_rb64(pb);
282  /* get also filesize */
283  if (pb->seekable) {
284  ffm->file_size = avio_size(pb);
285  if (ffm->write_index && 0)
287  } else {
288  ffm->file_size = (UINT64_C(1) << 63) - 1;
289  }
290 
291  while(!avio_feof(pb)) {
292  unsigned id = avio_rb32(pb);
293  unsigned size = avio_rb32(pb);
294  int64_t next = avio_tell(pb) + size;
295  char rc_eq_buf[128];
296 
297  if(!id)
298  break;
299 
300  switch(id) {
301  case MKBETAG('M', 'A', 'I', 'N'):
302  if (f_main++) {
303  ret = AVERROR(EINVAL);
304  goto fail;
305  }
306  avio_rb32(pb); /* nb_streams */
307  avio_rb32(pb); /* total bitrate */
308  break;
309  case MKBETAG('C', 'O', 'M', 'M'):
310  f_cprv = f_stvi = f_stau = 0;
311  st = avformat_new_stream(s, NULL);
312  if (!st) {
313  ret = AVERROR(ENOMEM);
314  goto fail;
315  }
316 
317  avpriv_set_pts_info(st, 64, 1, 1000000);
318 
319  codec = st->codec;
320  /* generic info */
321  codec->codec_id = avio_rb32(pb);
322  codec->codec_type = avio_r8(pb);
323  codec->bit_rate = avio_rb32(pb);
324  codec->flags = avio_rb32(pb);
325  codec->flags2 = avio_rb32(pb);
326  codec->debug = avio_rb32(pb);
327  if (codec->flags & CODEC_FLAG_GLOBAL_HEADER) {
328  if (ff_get_extradata(codec, pb, avio_rb32(pb)) < 0)
329  return AVERROR(ENOMEM);
330  }
331  break;
332  case MKBETAG('S', 'T', 'V', 'I'):
333  if (f_stvi++) {
334  ret = AVERROR(EINVAL);
335  goto fail;
336  }
337  codec->time_base.num = avio_rb32(pb);
338  codec->time_base.den = avio_rb32(pb);
339  if (codec->time_base.num <= 0 || codec->time_base.den <= 0) {
340  av_log(s, AV_LOG_ERROR, "Invalid time base %d/%d\n",
341  codec->time_base.num, codec->time_base.den);
342  ret = AVERROR_INVALIDDATA;
343  goto fail;
344  }
345  codec->width = avio_rb16(pb);
346  codec->height = avio_rb16(pb);
347  codec->gop_size = avio_rb16(pb);
348  codec->pix_fmt = avio_rb32(pb);
349  codec->qmin = avio_r8(pb);
350  codec->qmax = avio_r8(pb);
351  codec->max_qdiff = avio_r8(pb);
352  codec->qcompress = avio_rb16(pb) / 10000.0;
353  codec->qblur = avio_rb16(pb) / 10000.0;
354  codec->bit_rate_tolerance = avio_rb32(pb);
355  avio_get_str(pb, INT_MAX, rc_eq_buf, sizeof(rc_eq_buf));
356  codec->rc_eq = av_strdup(rc_eq_buf);
357  codec->rc_max_rate = avio_rb32(pb);
358  codec->rc_min_rate = avio_rb32(pb);
359  codec->rc_buffer_size = avio_rb32(pb);
360  codec->i_quant_factor = av_int2double(avio_rb64(pb));
361  codec->b_quant_factor = av_int2double(avio_rb64(pb));
362  codec->i_quant_offset = av_int2double(avio_rb64(pb));
363  codec->b_quant_offset = av_int2double(avio_rb64(pb));
364  codec->dct_algo = avio_rb32(pb);
365  codec->strict_std_compliance = avio_rb32(pb);
366  codec->max_b_frames = avio_rb32(pb);
367  codec->mpeg_quant = avio_rb32(pb);
368  codec->intra_dc_precision = avio_rb32(pb);
369  codec->me_method = avio_rb32(pb);
370  codec->mb_decision = avio_rb32(pb);
371  codec->nsse_weight = avio_rb32(pb);
372  codec->frame_skip_cmp = avio_rb32(pb);
374  codec->codec_tag = avio_rb32(pb);
375  codec->thread_count = avio_r8(pb);
376  codec->coder_type = avio_rb32(pb);
377  codec->me_cmp = avio_rb32(pb);
378  codec->me_subpel_quality = avio_rb32(pb);
379  codec->me_range = avio_rb32(pb);
380  codec->keyint_min = avio_rb32(pb);
381  codec->scenechange_threshold = avio_rb32(pb);
382  codec->b_frame_strategy = avio_rb32(pb);
383  codec->qcompress = av_int2double(avio_rb64(pb));
384  codec->qblur = av_int2double(avio_rb64(pb));
385  codec->max_qdiff = avio_rb32(pb);
386  codec->refs = avio_rb32(pb);
387  break;
388  case MKBETAG('S', 'T', 'A', 'U'):
389  if (f_stau++) {
390  ret = AVERROR(EINVAL);
391  goto fail;
392  }
393  codec->sample_rate = avio_rb32(pb);
394  codec->channels = avio_rl16(pb);
395  codec->frame_size = avio_rl16(pb);
396  break;
397  case MKBETAG('C', 'P', 'R', 'V'):
398  if (f_cprv++) {
399  ret = AVERROR(EINVAL);
400  goto fail;
401  }
402  enc = avcodec_find_encoder(codec->codec_id);
403  if (enc && enc->priv_data_size && enc->priv_class) {
404  buffer = av_malloc(size + 1);
405  if (!buffer) {
406  ret = AVERROR(ENOMEM);
407  goto fail;
408  }
409  avio_get_str(pb, size, buffer, size + 1);
410  if ((ret = ffm_append_recommended_configuration(st, &buffer)) < 0)
411  goto fail;
412  }
413  break;
414  case MKBETAG('S', '2', 'V', 'I'):
415  if (f_stvi++) {
416  ret = AVERROR(EINVAL);
417  goto fail;
418  }
419  buffer = av_malloc(size);
420  if (!buffer) {
421  ret = AVERROR(ENOMEM);
422  goto fail;
423  }
424  avio_get_str(pb, INT_MAX, buffer, size);
425  av_set_options_string(codec, buffer, "=", ",");
426  if ((ret = ffm_append_recommended_configuration(st, &buffer)) < 0)
427  goto fail;
428  break;
429  case MKBETAG('S', '2', 'A', 'U'):
430  if (f_stau++) {
431  ret = AVERROR(EINVAL);
432  goto fail;
433  }
434  buffer = av_malloc(size);
435  if (!buffer) {
436  ret = AVERROR(ENOMEM);
437  goto fail;
438  }
439  avio_get_str(pb, INT_MAX, buffer, size);
440  av_set_options_string(codec, buffer, "=", ",");
442  break;
443  }
444  avio_seek(pb, next, SEEK_SET);
445  }
446 
447  /* get until end of block reached */
448  while ((avio_tell(pb) % ffm->packet_size) != 0 && !pb->eof_reached)
449  avio_r8(pb);
450 
451  /* init packet demux */
452  ffm->packet_ptr = ffm->packet;
453  ffm->packet_end = ffm->packet;
454  ffm->frame_offset = 0;
455  ffm->dts = 0;
456  ffm->read_state = READ_HEADER;
457  ffm->first_packet = 1;
458  return 0;
459  fail:
460  ffm_close(s);
461  return ret;
462 }
463 
465 {
466  FFMContext *ffm = s->priv_data;
467  AVStream *st;
468  AVIOContext *pb = s->pb;
469  AVCodecContext *codec;
470  int i, nb_streams;
471  uint32_t tag;
472 
473  /* header */
474  tag = avio_rl32(pb);
475  if (tag == MKTAG('F', 'F', 'M', '2'))
476  return ffm2_read_header(s);
477  if (tag != MKTAG('F', 'F', 'M', '1'))
478  goto fail;
479  ffm->packet_size = avio_rb32(pb);
480  if (ffm->packet_size != FFM_PACKET_SIZE)
481  goto fail;
482  ffm->write_index = avio_rb64(pb);
483  /* get also filesize */
484  if (pb->seekable) {
485  ffm->file_size = avio_size(pb);
486  if (ffm->write_index && 0)
488  } else {
489  ffm->file_size = (UINT64_C(1) << 63) - 1;
490  }
491 
492  nb_streams = avio_rb32(pb);
493  avio_rb32(pb); /* total bitrate */
494  /* read each stream */
495  for(i=0;i<nb_streams;i++) {
496  char rc_eq_buf[128];
497 
498  st = avformat_new_stream(s, NULL);
499  if (!st)
500  goto fail;
501 
502  avpriv_set_pts_info(st, 64, 1, 1000000);
503 
504  codec = st->codec;
505  /* generic info */
506  codec->codec_id = avio_rb32(pb);
507  codec->codec_type = avio_r8(pb); /* codec_type */
508  codec->bit_rate = avio_rb32(pb);
509  codec->flags = avio_rb32(pb);
510  codec->flags2 = avio_rb32(pb);
511  codec->debug = avio_rb32(pb);
512  /* specific info */
513  switch(codec->codec_type) {
514  case AVMEDIA_TYPE_VIDEO:
515  codec->time_base.num = avio_rb32(pb);
516  codec->time_base.den = avio_rb32(pb);
517  if (codec->time_base.num <= 0 || codec->time_base.den <= 0) {
518  av_log(s, AV_LOG_ERROR, "Invalid time base %d/%d\n",
519  codec->time_base.num, codec->time_base.den);
520  goto fail;
521  }
522  codec->width = avio_rb16(pb);
523  codec->height = avio_rb16(pb);
524  codec->gop_size = avio_rb16(pb);
525  codec->pix_fmt = avio_rb32(pb);
526  codec->qmin = avio_r8(pb);
527  codec->qmax = avio_r8(pb);
528  codec->max_qdiff = avio_r8(pb);
529  codec->qcompress = avio_rb16(pb) / 10000.0;
530  codec->qblur = avio_rb16(pb) / 10000.0;
531  codec->bit_rate_tolerance = avio_rb32(pb);
532  avio_get_str(pb, INT_MAX, rc_eq_buf, sizeof(rc_eq_buf));
533  codec->rc_eq = av_strdup(rc_eq_buf);
534  codec->rc_max_rate = avio_rb32(pb);
535  codec->rc_min_rate = avio_rb32(pb);
536  codec->rc_buffer_size = avio_rb32(pb);
537  codec->i_quant_factor = av_int2double(avio_rb64(pb));
538  codec->b_quant_factor = av_int2double(avio_rb64(pb));
539  codec->i_quant_offset = av_int2double(avio_rb64(pb));
540  codec->b_quant_offset = av_int2double(avio_rb64(pb));
541  codec->dct_algo = avio_rb32(pb);
542  codec->strict_std_compliance = avio_rb32(pb);
543  codec->max_b_frames = avio_rb32(pb);
544  codec->mpeg_quant = avio_rb32(pb);
545  codec->intra_dc_precision = avio_rb32(pb);
546  codec->me_method = avio_rb32(pb);
547  codec->mb_decision = avio_rb32(pb);
548  codec->nsse_weight = avio_rb32(pb);
549  codec->frame_skip_cmp = avio_rb32(pb);
551  codec->codec_tag = avio_rb32(pb);
552  codec->thread_count = avio_r8(pb);
553  codec->coder_type = avio_rb32(pb);
554  codec->me_cmp = avio_rb32(pb);
555  codec->me_subpel_quality = avio_rb32(pb);
556  codec->me_range = avio_rb32(pb);
557  codec->keyint_min = avio_rb32(pb);
558  codec->scenechange_threshold = avio_rb32(pb);
559  codec->b_frame_strategy = avio_rb32(pb);
560  codec->qcompress = av_int2double(avio_rb64(pb));
561  codec->qblur = av_int2double(avio_rb64(pb));
562  codec->max_qdiff = avio_rb32(pb);
563  codec->refs = avio_rb32(pb);
564  break;
565  case AVMEDIA_TYPE_AUDIO:
566  codec->sample_rate = avio_rb32(pb);
567  codec->channels = avio_rl16(pb);
568  codec->frame_size = avio_rl16(pb);
569  break;
570  default:
571  goto fail;
572  }
573  if (codec->flags & CODEC_FLAG_GLOBAL_HEADER) {
574  if (ff_get_extradata(codec, pb, avio_rb32(pb)) < 0)
575  return AVERROR(ENOMEM);
576  }
577  }
578 
579  /* get until end of block reached */
580  while ((avio_tell(pb) % ffm->packet_size) != 0 && !pb->eof_reached)
581  avio_r8(pb);
582 
583  /* init packet demux */
584  ffm->packet_ptr = ffm->packet;
585  ffm->packet_end = ffm->packet;
586  ffm->frame_offset = 0;
587  ffm->dts = 0;
588  ffm->read_state = READ_HEADER;
589  ffm->first_packet = 1;
590  return 0;
591  fail:
592  ffm_close(s);
593  return -1;
594 }
595 
596 /* return < 0 if eof */
598 {
599  int size;
600  FFMContext *ffm = s->priv_data;
601  int duration, ret;
602 
603  switch(ffm->read_state) {
604  case READ_HEADER:
605  if ((ret = ffm_is_avail_data(s, FRAME_HEADER_SIZE+4)) < 0)
606  return ret;
607 
608  av_dlog(s, "pos=%08"PRIx64" spos=%"PRIx64", write_index=%"PRIx64" size=%"PRIx64"\n",
609  avio_tell(s->pb), s->pb->pos, ffm->write_index, ffm->file_size);
610  if (ffm_read_data(s, ffm->header, FRAME_HEADER_SIZE, 1) !=
612  return -1;
613  if (ffm->header[1] & FLAG_DTS)
614  if (ffm_read_data(s, ffm->header+16, 4, 1) != 4)
615  return -1;
616  ffm->read_state = READ_DATA;
617  /* fall through */
618  case READ_DATA:
619  size = AV_RB24(ffm->header + 2);
620  if ((ret = ffm_is_avail_data(s, size)) < 0)
621  return ret;
622 
623  duration = AV_RB24(ffm->header + 5);
624 
625  if (av_new_packet(pkt, size) < 0) {
626  return AVERROR(ENOMEM);
627  }
628  pkt->stream_index = ffm->header[0];
629  if ((unsigned)pkt->stream_index >= s->nb_streams) {
630  av_log(s, AV_LOG_ERROR, "invalid stream index %d\n", pkt->stream_index);
631  av_free_packet(pkt);
632  ffm->read_state = READ_HEADER;
633  return -1;
634  }
635  pkt->pos = avio_tell(s->pb);
636  if (ffm->header[1] & FLAG_KEY_FRAME)
637  pkt->flags |= AV_PKT_FLAG_KEY;
638 
639  ffm->read_state = READ_HEADER;
640  if (ffm_read_data(s, pkt->data, size, 0) != size) {
641  /* bad case: desynchronized packet. we cancel all the packet loading */
642  av_free_packet(pkt);
643  return -1;
644  }
645  pkt->pts = AV_RB64(ffm->header+8);
646  if (ffm->header[1] & FLAG_DTS)
647  pkt->dts = pkt->pts - AV_RB32(ffm->header+16);
648  else
649  pkt->dts = pkt->pts;
650  pkt->duration = duration;
651  break;
652  }
653  return 0;
654 }
655 
656 /* seek to a given time in the file. The file read pointer is
657  positioned at or before pts. XXX: the following code is quite
658  approximative */
659 static int ffm_seek(AVFormatContext *s, int stream_index, int64_t wanted_pts, int flags)
660 {
661  FFMContext *ffm = s->priv_data;
662  int64_t pos_min, pos_max, pos;
663  int64_t pts_min, pts_max, pts;
664  double pos1;
665 
666  av_dlog(s, "wanted_pts=%0.6f\n", wanted_pts / 1000000.0);
667  /* find the position using linear interpolation (better than
668  dichotomy in typical cases) */
669  if (ffm->write_index && ffm->write_index < ffm->file_size) {
670  if (get_dts(s, FFM_PACKET_SIZE) < wanted_pts) {
671  pos_min = FFM_PACKET_SIZE;
672  pos_max = ffm->write_index - FFM_PACKET_SIZE;
673  } else {
674  pos_min = ffm->write_index;
675  pos_max = ffm->file_size - FFM_PACKET_SIZE;
676  }
677  } else {
678  pos_min = FFM_PACKET_SIZE;
679  pos_max = ffm->file_size - FFM_PACKET_SIZE;
680  }
681  while (pos_min <= pos_max) {
682  pts_min = get_dts(s, pos_min);
683  pts_max = get_dts(s, pos_max);
684  if (pts_min > wanted_pts || pts_max <= wanted_pts) {
685  pos = pts_min > wanted_pts ? pos_min : pos_max;
686  goto found;
687  }
688  /* linear interpolation */
689  pos1 = (double)(pos_max - pos_min) * (double)(wanted_pts - pts_min) /
690  (double)(pts_max - pts_min);
691  pos = (((int64_t)pos1) / FFM_PACKET_SIZE) * FFM_PACKET_SIZE;
692  if (pos <= pos_min)
693  pos = pos_min;
694  else if (pos >= pos_max)
695  pos = pos_max;
696  pts = get_dts(s, pos);
697  /* check if we are lucky */
698  if (pts == wanted_pts) {
699  goto found;
700  } else if (pts > wanted_pts) {
701  pos_max = pos - FFM_PACKET_SIZE;
702  } else {
703  pos_min = pos + FFM_PACKET_SIZE;
704  }
705  }
706  pos = (flags & AVSEEK_FLAG_BACKWARD) ? pos_min : pos_max;
707 
708  found:
709  if (ffm_seek1(s, pos) < 0)
710  return -1;
711 
712  /* reset read state */
713  ffm->read_state = READ_HEADER;
714  ffm->packet_ptr = ffm->packet;
715  ffm->packet_end = ffm->packet;
716  ffm->first_packet = 1;
717 
718  return 0;
719 }
720 
721 static int ffm_probe(AVProbeData *p)
722 {
723  if (
724  p->buf[0] == 'F' && p->buf[1] == 'F' && p->buf[2] == 'M' &&
725  (p->buf[3] == '1' || p->buf[3] == '2'))
726  return AVPROBE_SCORE_MAX + 1;
727  return 0;
728 }
729 
731  .name = "ffm",
732  .long_name = NULL_IF_CONFIG_SMALL("FFM (FFserver live feed)"),
733  .priv_data_size = sizeof(FFMContext),
738  .read_seek = ffm_seek,
739 };