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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 
33 typedef struct {
36 
37 static int webvtt_probe(AVProbeData *p)
38 {
39  const uint8_t *ptr = p->buf;
40 
41  if (AV_RB24(ptr) == 0xEFBBBF)
42  ptr += 3; /* skip UTF-8 BOM */
43  if (!strncmp(ptr, "WEBVTT", 6) &&
44  (!ptr[6] || strchr("\n\r\t ", ptr[6])))
45  return AVPROBE_SCORE_MAX;
46  return 0;
47 }
48 
49 static int64_t read_ts(const char *s)
50 {
51  int hh, mm, ss, ms;
52  if (sscanf(s, "%u:%u:%u.%u", &hh, &mm, &ss, &ms) == 4) return (hh*3600LL + mm*60LL + ss) * 1000LL + ms;
53  if (sscanf(s, "%u:%u.%u", &mm, &ss, &ms) == 3) return ( mm*60LL + ss) * 1000LL + ms;
54  return AV_NOPTS_VALUE;
55 }
56 
58 {
59  WebVTTContext *webvtt = s->priv_data;
60  AVBPrint header, cue;
61  int res = 0;
63 
64  if (!st)
65  return AVERROR(ENOMEM);
66  avpriv_set_pts_info(st, 64, 1, 1000);
69 
72 
73  for (;;) {
74  int i;
75  int64_t pos;
76  AVPacket *sub;
77  const char *p, *identifier;
78  //const char *settings = NULL;
79  int64_t ts_start, ts_end;
80 
81  ff_subtitles_read_chunk(s->pb, &cue);
82 
83  if (!cue.len)
84  break;
85 
86  p = identifier = cue.str;
87  pos = avio_tell(s->pb);
88 
89  /* ignore header chunk */
90  if (!strncmp(p, "\xEF\xBB\xBFWEBVTT", 9) ||
91  !strncmp(p, "WEBVTT", 6))
92  continue;
93 
94  /* optional cue identifier (can be a number like in SRT or some kind of
95  * chaptering id), silently skip it */
96  for (i = 0; p[i] && p[i] != '\n'; i++) {
97  if (!strncmp(p + i, "-->", 3)) {
98  identifier = NULL;
99  break;
100  }
101  }
102  if (identifier)
103  p += strcspn(p, "\n");
104 
105  /* cue timestamps */
106  if ((ts_start = read_ts(p)) == AV_NOPTS_VALUE)
107  break;
108  if (!(p = strstr(p, "-->")))
109  break;
110  p += 3;
111  do p++; while (*p == ' ' || *p == '\t');
112  if ((ts_end = read_ts(p)) == AV_NOPTS_VALUE)
113  break;
114 
115  /* optional cue settings, TODO: store in side_data */
116  p += strcspn(p, "\n\t ");
117  while (*p == '\t' || *p == ' ')
118  p++;
119  if (*p != '\n') {
120  //settings = p;
121  p += strcspn(p, "\n");
122  }
123  if (*p == '\n')
124  p++;
125 
126  /* create packet */
127  sub = ff_subtitles_queue_insert(&webvtt->q, p, strlen(p), 0);
128  if (!sub) {
129  res = AVERROR(ENOMEM);
130  goto end;
131  }
132  sub->pos = pos;
133  sub->pts = ts_start;
134  sub->duration = ts_end - ts_start;
135  }
136 
137  ff_subtitles_queue_finalize(&webvtt->q);
138 
139 end:
140  av_bprint_finalize(&cue, NULL);
141  av_bprint_finalize(&header, NULL);
142  return res;
143 }
144 
146 {
147  WebVTTContext *webvtt = s->priv_data;
148  return ff_subtitles_queue_read_packet(&webvtt->q, pkt);
149 }
150 
151 static int webvtt_read_seek(AVFormatContext *s, int stream_index,
152  int64_t min_ts, int64_t ts, int64_t max_ts, int flags)
153 {
154  WebVTTContext *webvtt = s->priv_data;
155  return ff_subtitles_queue_seek(&webvtt->q, s, stream_index,
156  min_ts, ts, max_ts, flags);
157 }
158 
160 {
161  WebVTTContext *webvtt = s->priv_data;
162  ff_subtitles_queue_clean(&webvtt->q);
163  return 0;
164 }
165 
167  .name = "webvtt",
168  .long_name = NULL_IF_CONFIG_SMALL("WebVTT subtitle"),
169  .priv_data_size = sizeof(WebVTTContext),
173  .read_seek2 = webvtt_read_seek,
175  .extensions = "vtt",
176 };