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tedcaptionsdec.c
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1 /*
2  * TED Talks captions format decoder
3  * Copyright (c) 2012 Nicolas George
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 "libavutil/bprint.h"
23 #include "libavutil/log.h"
24 #include "libavutil/opt.h"
25 #include "avformat.h"
26 #include "internal.h"
27 #include "subtitles.h"
28 
29 typedef struct {
30  AVClass *class;
31  int64_t start_time;
34 
35 static const AVOption tedcaptions_options[] = {
36  { "start_time", "set the start time (offset) of the subtitles, in ms",
38  { .i64 = 15000 }, INT64_MIN, INT64_MAX,
40  { NULL },
41 };
42 
44  .class_name = "tedcaptions_demuxer",
45  .item_name = av_default_item_name,
46  .option = tedcaptions_options,
47  .version = LIBAVUTIL_VERSION_INT,
48 };
49 
50 #define BETWEEN(a, amin, amax) ((unsigned)((a) - (amin)) <= (amax) - (amin))
51 
52 #define HEX_DIGIT_TEST(c) (BETWEEN(c, '0', '9') || BETWEEN((c) | 32, 'a', 'z'))
53 #define HEX_DIGIT_VAL(c) ((c) <= '9' ? (c) - '0' : ((c) | 32) - 'a' + 10)
54 #define ERR_CODE(c) (c < 0 ? c : AVERROR_INVALIDDATA)
55 
56 static void av_bprint_utf8(AVBPrint *bp, unsigned c)
57 {
58  int bytes, i;
59 
60  if (c <= 0x7F) {
61  av_bprint_chars(bp, c, 1);
62  return;
63  }
64  bytes = (av_log2(c) - 2) / 5;
65  av_bprint_chars(bp, (c >> (bytes * 6)) | ((0xFF80 >> bytes) & 0xFF), 1);
66  for (i = bytes - 1; i >= 0; i--)
67  av_bprint_chars(bp, ((c >> (i * 6)) & 0x3F) | 0x80, 1);
68 }
69 
70 static void next_byte(AVIOContext *pb, int *cur_byte)
71 {
72  uint8_t b;
73  int ret = avio_read(pb, &b, 1);
74  *cur_byte = ret > 0 ? b : ret == 0 ? AVERROR_EOF : ret;
75 }
76 
77 static void skip_spaces(AVIOContext *pb, int *cur_byte)
78 {
79  while (*cur_byte == ' ' || *cur_byte == '\t' ||
80  *cur_byte == '\n' || *cur_byte == '\r')
81  next_byte(pb, cur_byte);
82 }
83 
84 static int expect_byte(AVIOContext *pb, int *cur_byte, uint8_t c)
85 {
86  skip_spaces(pb, cur_byte);
87  if (*cur_byte != c)
88  return ERR_CODE(*cur_byte);
89  next_byte(pb, cur_byte);
90  return 0;
91 }
92 
93 static int parse_string(AVIOContext *pb, int *cur_byte, AVBPrint *bp, int full)
94 {
95  int ret;
96 
97  av_bprint_init(bp, 0, full ? -1 : 1);
98  ret = expect_byte(pb, cur_byte, '"');
99  if (ret < 0)
100  goto fail;
101  while (*cur_byte > 0 && *cur_byte != '"') {
102  if (*cur_byte == '\\') {
103  next_byte(pb, cur_byte);
104  if (*cur_byte < 0) {
105  ret = AVERROR_INVALIDDATA;
106  goto fail;
107  }
108  if ((*cur_byte | 32) == 'u') {
109  unsigned chr = 0, i;
110  for (i = 0; i < 4; i++) {
111  next_byte(pb, cur_byte);
112  if (!HEX_DIGIT_TEST(*cur_byte)) {
113  ret = ERR_CODE(*cur_byte);
114  goto fail;
115  }
116  chr = chr * 16 + HEX_DIGIT_VAL(*cur_byte);
117  }
118  av_bprint_utf8(bp, chr);
119  } else {
120  av_bprint_chars(bp, *cur_byte, 1);
121  }
122  } else {
123  av_bprint_chars(bp, *cur_byte, 1);
124  }
125  next_byte(pb, cur_byte);
126  }
127  ret = expect_byte(pb, cur_byte, '"');
128  if (ret < 0)
129  goto fail;
130  if (full && !av_bprint_is_complete(bp)) {
131  ret = AVERROR(ENOMEM);
132  goto fail;
133  }
134  return 0;
135 
136 fail:
138  return ret;
139 }
140 
141 static int parse_label(AVIOContext *pb, int *cur_byte, AVBPrint *bp)
142 {
143  int ret;
144 
145  ret = parse_string(pb, cur_byte, bp, 0);
146  if (ret < 0)
147  return ret;
148  ret = expect_byte(pb, cur_byte, ':');
149  if (ret < 0)
150  return ret;
151  return 0;
152 }
153 
154 static int parse_boolean(AVIOContext *pb, int *cur_byte, int *result)
155 {
156  const char *text[] = { "false", "true" }, *p;
157  int i;
158 
159  skip_spaces(pb, cur_byte);
160  for (i = 0; i < 2; i++) {
161  p = text[i];
162  if (*cur_byte != *p)
163  continue;
164  for (; *p; p++, next_byte(pb, cur_byte))
165  if (*cur_byte != *p)
166  return AVERROR_INVALIDDATA;
167  if (BETWEEN(*cur_byte | 32, 'a', 'z'))
168  return AVERROR_INVALIDDATA;
169  *result = i;
170  return 0;
171  }
172  return AVERROR_INVALIDDATA;
173 }
174 
175 static int parse_int(AVIOContext *pb, int *cur_byte, int64_t *result)
176 {
177  int64_t val = 0;
178 
179  skip_spaces(pb, cur_byte);
180  if ((unsigned)*cur_byte - '0' > 9)
181  return AVERROR_INVALIDDATA;
182  while (BETWEEN(*cur_byte, '0', '9')) {
183  val = val * 10 + (*cur_byte - '0');
184  next_byte(pb, cur_byte);
185  }
186  *result = val;
187  return 0;
188 }
189 
191 {
192  int ret, cur_byte, start_of_par;
193  AVBPrint label, content;
194  int64_t pos, start, duration;
195  AVPacket *pkt;
196 
197  next_byte(pb, &cur_byte);
198  ret = expect_byte(pb, &cur_byte, '{');
199  if (ret < 0)
200  return AVERROR_INVALIDDATA;
201  ret = parse_label(pb, &cur_byte, &label);
202  if (ret < 0 || strcmp(label.str, "captions"))
203  return AVERROR_INVALIDDATA;
204  ret = expect_byte(pb, &cur_byte, '[');
205  if (ret < 0)
206  return AVERROR_INVALIDDATA;
207  while (1) {
208  content.size = 0;
209  start = duration = AV_NOPTS_VALUE;
210  ret = expect_byte(pb, &cur_byte, '{');
211  if (ret < 0)
212  return ret;
213  pos = avio_tell(pb) - 1;
214  while (1) {
215  ret = parse_label(pb, &cur_byte, &label);
216  if (ret < 0)
217  return ret;
218  if (!strcmp(label.str, "startOfParagraph")) {
219  ret = parse_boolean(pb, &cur_byte, &start_of_par);
220  if (ret < 0)
221  return ret;
222  } else if (!strcmp(label.str, "content")) {
223  ret = parse_string(pb, &cur_byte, &content, 1);
224  if (ret < 0)
225  return ret;
226  } else if (!strcmp(label.str, "startTime")) {
227  ret = parse_int(pb, &cur_byte, &start);
228  if (ret < 0)
229  return ret;
230  } else if (!strcmp(label.str, "duration")) {
231  ret = parse_int(pb, &cur_byte, &duration);
232  if (ret < 0)
233  return ret;
234  } else {
235  return AVERROR_INVALIDDATA;
236  }
237  skip_spaces(pb, &cur_byte);
238  if (cur_byte != ',')
239  break;
240  next_byte(pb, &cur_byte);
241  }
242  ret = expect_byte(pb, &cur_byte, '}');
243  if (ret < 0)
244  return ret;
245 
246  if (!content.size || start == AV_NOPTS_VALUE ||
247  duration == AV_NOPTS_VALUE)
248  return AVERROR_INVALIDDATA;
249  pkt = ff_subtitles_queue_insert(subs, content.str, content.len, 0);
250  if (!pkt)
251  return AVERROR(ENOMEM);
252  pkt->pos = pos;
253  pkt->pts = start;
254  pkt->duration = duration;
255  av_bprint_finalize(&content, NULL);
256 
257  skip_spaces(pb, &cur_byte);
258  if (cur_byte != ',')
259  break;
260  next_byte(pb, &cur_byte);
261  }
262  ret = expect_byte(pb, &cur_byte, ']');
263  if (ret < 0)
264  return ret;
265  ret = expect_byte(pb, &cur_byte, '}');
266  if (ret < 0)
267  return ret;
268  skip_spaces(pb, &cur_byte);
269  if (cur_byte != AVERROR_EOF)
270  return ERR_CODE(cur_byte);
271  return 0;
272 }
273 
275 {
276  TEDCaptionsDemuxer *tc = avf->priv_data;
277  AVStream *st;
278  int ret, i;
279  AVPacket *last;
280 
281  ret = parse_file(avf->pb, &tc->subs);
282  if (ret < 0) {
283  if (ret == AVERROR_INVALIDDATA)
284  av_log(avf, AV_LOG_ERROR, "Syntax error near offset %"PRId64".\n",
285  avio_tell(avf->pb));
287  return ret;
288  }
290  for (i = 0; i < tc->subs.nb_subs; i++)
291  tc->subs.subs[i].pts += tc->start_time;
292 
293  last = &tc->subs.subs[tc->subs.nb_subs - 1];
294  st = avformat_new_stream(avf, NULL);
295  if (!st)
296  return AVERROR(ENOMEM);
299  avpriv_set_pts_info(st, 64, 1, 1000);
300  st->probe_packets = 0;
301  st->start_time = 0;
302  st->duration = last->pts + last->duration;
303  st->cur_dts = 0;
304 
305  return 0;
306 }
307 
309 {
310  TEDCaptionsDemuxer *tc = avf->priv_data;
311 
312  return ff_subtitles_queue_read_packet(&tc->subs, packet);
313 }
314 
316 {
317  TEDCaptionsDemuxer *tc = avf->priv_data;
318 
320  return 0;
321 }
322 
324 {
325  static const char *const tags[] = {
326  "\"captions\"", "\"duration\"", "\"content\"",
327  "\"startOfParagraph\"", "\"startTime\"",
328  };
329  unsigned i, count = 0;
330  const char *t;
331 
332  if (p->buf[strspn(p->buf, " \t\r\n")] != '{')
333  return 0;
334  for (i = 0; i < FF_ARRAY_ELEMS(tags); i++) {
335  if (!(t = strstr(p->buf, tags[i])))
336  continue;
337  t += strlen(tags[i]);
338  t += strspn(t, " \t\r\n");
339  if (*t == ':')
340  count++;
341  }
342  return count == FF_ARRAY_ELEMS(tags) ? AVPROBE_SCORE_MAX :
343  count ? AVPROBE_SCORE_MAX / 2 : 0;
344 }
345 
346 static int tedcaptions_read_seek(AVFormatContext *avf, int stream_index,
347  int64_t min_ts, int64_t ts, int64_t max_ts,
348  int flags)
349 {
350  TEDCaptionsDemuxer *tc = avf->priv_data;
351  return ff_subtitles_queue_seek(&tc->subs, avf, stream_index,
352  min_ts, ts, max_ts, flags);
353 }
354 
356  .name = "tedcaptions",
357  .long_name = NULL_IF_CONFIG_SMALL("TED Talks captions"),
358  .priv_data_size = sizeof(TEDCaptionsDemuxer),
359  .priv_class = &tedcaptions_demuxer_class,
364  .read_seek2 = tedcaptions_read_seek,
365 };