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webvttdec.c
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1 /*
2  * Copyright (c) 2012 Clément Bœsch
3  *
4  * This file is part of FFmpeg.
5  *
6  * FFmpeg is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * FFmpeg is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with FFmpeg; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 /**
22  * @file
23  * WebVTT subtitle demuxer
24  * @see http://dev.w3.org/html5/webvtt/
25  */
26 
27 #include "avformat.h"
28 #include "internal.h"
29 #include "subtitles.h"
30 #include "libavutil/bprint.h"
31 #include "libavutil/intreadwrite.h"
32 #include "libavutil/opt.h"
33 
34 typedef struct {
35  const AVClass *class;
37  int kind;
39 
40 static int webvtt_probe(AVProbeData *p)
41 {
42  const uint8_t *ptr = p->buf;
43 
44  if (AV_RB24(ptr) == 0xEFBBBF)
45  ptr += 3; /* skip UTF-8 BOM */
46  if (!strncmp(ptr, "WEBVTT", 6) &&
47  (!ptr[6] || strchr("\n\r\t ", ptr[6])))
48  return AVPROBE_SCORE_MAX;
49  return 0;
50 }
51 
52 static int64_t read_ts(const char *s)
53 {
54  int hh, mm, ss, ms;
55  if (sscanf(s, "%u:%u:%u.%u", &hh, &mm, &ss, &ms) == 4) return (hh*3600LL + mm*60LL + ss) * 1000LL + ms;
56  if (sscanf(s, "%u:%u.%u", &mm, &ss, &ms) == 3) return ( mm*60LL + ss) * 1000LL + ms;
57  return AV_NOPTS_VALUE;
58 }
59 
61 {
62  WebVTTContext *webvtt = s->priv_data;
63  AVBPrint header, cue;
64  int res = 0;
66 
67  if (!st)
68  return AVERROR(ENOMEM);
69  avpriv_set_pts_info(st, 64, 1, 1000);
72  st->disposition |= webvtt->kind;
73 
76 
77  for (;;) {
78  int i;
79  int64_t pos;
80  AVPacket *sub;
81  const char *p, *identifier, *settings;
82  int identifier_len, settings_len;
83  int64_t ts_start, ts_end;
84 
85  ff_subtitles_read_chunk(s->pb, &cue);
86 
87  if (!cue.len)
88  break;
89 
90  p = identifier = cue.str;
91  pos = avio_tell(s->pb);
92 
93  /* ignore header chunk */
94  if (!strncmp(p, "\xEF\xBB\xBFWEBVTT", 9) ||
95  !strncmp(p, "WEBVTT", 6))
96  continue;
97 
98  /* optional cue identifier (can be a number like in SRT or some kind of
99  * chaptering id) */
100  for (i = 0; p[i] && p[i] != '\n' && p[i] != '\r'; i++) {
101  if (!strncmp(p + i, "-->", 3)) {
102  identifier = NULL;
103  break;
104  }
105  }
106  if (!identifier)
107  identifier_len = 0;
108  else {
109  identifier_len = strcspn(p, "\r\n");
110  p += identifier_len;
111  if (*p == '\r')
112  p++;
113  if (*p == '\n')
114  p++;
115  }
116 
117  /* cue timestamps */
118  if ((ts_start = read_ts(p)) == AV_NOPTS_VALUE)
119  break;
120  if (!(p = strstr(p, "-->")))
121  break;
122  p += 2;
123  do p++; while (*p == ' ' || *p == '\t');
124  if ((ts_end = read_ts(p)) == AV_NOPTS_VALUE)
125  break;
126 
127  /* optional cue settings */
128  p += strcspn(p, "\n\t ");
129  while (*p == '\t' || *p == ' ')
130  p++;
131  settings = p;
132  settings_len = strcspn(p, "\r\n");
133  p += settings_len;
134  if (*p == '\r')
135  p++;
136  if (*p == '\n')
137  p++;
138 
139  /* create packet */
140  sub = ff_subtitles_queue_insert(&webvtt->q, p, strlen(p), 0);
141  if (!sub) {
142  res = AVERROR(ENOMEM);
143  goto end;
144  }
145  sub->pos = pos;
146  sub->pts = ts_start;
147  sub->duration = ts_end - ts_start;
148 
149 #define SET_SIDE_DATA(name, type) do { \
150  if (name##_len) { \
151  uint8_t *buf = av_packet_new_side_data(sub, type, name##_len); \
152  if (!buf) { \
153  res = AVERROR(ENOMEM); \
154  goto end; \
155  } \
156  memcpy(buf, name, name##_len); \
157  } \
158 } while (0)
159 
162  }
163 
164  ff_subtitles_queue_finalize(&webvtt->q);
165 
166 end:
167  av_bprint_finalize(&cue, NULL);
168  av_bprint_finalize(&header, NULL);
169  return res;
170 }
171 
173 {
174  WebVTTContext *webvtt = s->priv_data;
175  return ff_subtitles_queue_read_packet(&webvtt->q, pkt);
176 }
177 
178 static int webvtt_read_seek(AVFormatContext *s, int stream_index,
179  int64_t min_ts, int64_t ts, int64_t max_ts, int flags)
180 {
181  WebVTTContext *webvtt = s->priv_data;
182  return ff_subtitles_queue_seek(&webvtt->q, s, stream_index,
183  min_ts, ts, max_ts, flags);
184 }
185 
187 {
188  WebVTTContext *webvtt = s->priv_data;
189  ff_subtitles_queue_clean(&webvtt->q);
190  return 0;
191 }
192 
193 #define OFFSET(x) offsetof(WebVTTContext, x)
194 #define KIND_FLAGS AV_OPT_FLAG_SUBTITLE_PARAM
195 
196 static const AVOption options[] = {
197  { "kind", "Set kind of WebVTT track", OFFSET(kind), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, KIND_FLAGS, "webvtt_kind" },
198  { "subtitles", "WebVTT subtitles kind", 0, AV_OPT_TYPE_CONST, { .i64 = 0 }, INT_MIN, INT_MAX, 0, "webvtt_kind" },
199  { "captions", "WebVTT captions kind", 0, AV_OPT_TYPE_CONST, { .i64 = AV_DISPOSITION_CAPTIONS }, INT_MIN, INT_MAX, 0, "webvtt_kind" },
200  { "descriptions", "WebVTT descriptions kind", 0, AV_OPT_TYPE_CONST, { .i64 = AV_DISPOSITION_DESCRIPTIONS }, INT_MIN, INT_MAX, 0, "webvtt_kind" },
201  { "metadata", "WebVTT metadata kind", 0, AV_OPT_TYPE_CONST, { .i64 = AV_DISPOSITION_METADATA }, INT_MIN, INT_MAX, 0, "webvtt_kind" },
202  { NULL }
203 };
204 
206  .class_name = "WebVTT demuxer",
207  .item_name = av_default_item_name,
208  .option = options,
209  .version = LIBAVUTIL_VERSION_INT,
210 };
211 
213  .name = "webvtt",
214  .long_name = NULL_IF_CONFIG_SMALL("WebVTT subtitle"),
215  .priv_data_size = sizeof(WebVTTContext),
219  .read_seek2 = webvtt_read_seek,
221  .extensions = "vtt",
222  .priv_class = &webvtt_demuxer_class,
223 };