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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 decoder
24  * @see http://dev.w3.org/html5/webvtt/
25  * @todo need to support extended markups and cue settings
26  */
27 
28 #include "avcodec.h"
29 #include "ass.h"
30 #include "libavutil/bprint.h"
31 
32 static const struct {
33  const char *from;
34  const char *to;
35 } webvtt_tag_replace[] = {
36  {"<i>", "{\\i1}"}, {"</i>", "{\\i0}"},
37  {"<b>", "{\\b1}"}, {"</b>", "{\\b0}"},
38  {"<u>", "{\\u1}"}, {"</u>", "{\\u0}"},
39  {"{", "\\{"}, {"}", "\\}"}, // escape to avoid ASS markup conflicts
40 };
41 
42 static int webvtt_event_to_ass(AVBPrint *buf, const char *p)
43 {
44  int i, skip = 0;
45 
46  while (*p) {
47 
48  for (i = 0; i < FF_ARRAY_ELEMS(webvtt_tag_replace); i++) {
49  const char *from = webvtt_tag_replace[i].from;
50  const size_t len = strlen(from);
51  if (!strncmp(p, from, len)) {
52  av_bprintf(buf, "%s", webvtt_tag_replace[i].to);
53  p += len;
54  break;
55  }
56  }
57  if (!*p)
58  break;
59 
60  if (*p == '<')
61  skip = 1;
62  else if (*p == '>')
63  skip = 0;
64  else if (p[0] == '\n' && p[1])
65  av_bprintf(buf, "\\N");
66  else if (!skip && *p != '\r')
67  av_bprint_chars(buf, *p, 1);
68  p++;
69  }
70  av_bprintf(buf, "\r\n");
71  return 0;
72 }
73 
75  void *data, int *got_sub_ptr, AVPacket *avpkt)
76 {
77  int ret = 0;
78  AVSubtitle *sub = data;
79  const char *ptr = avpkt->data;
80  AVBPrint buf;
81 
83  if (ptr && avpkt->size > 0 && !webvtt_event_to_ass(&buf, ptr)) {
84  int ts_start = av_rescale_q(avpkt->pts, avctx->time_base, (AVRational){1,100});
85  int ts_duration = avpkt->duration != -1 ?
86  av_rescale_q(avpkt->duration, avctx->time_base, (AVRational){1,100}) : -1;
87  ret = ff_ass_add_rect_bprint(sub, &buf, ts_start, ts_duration, 0);
88  }
89  av_bprint_finalize(&buf, NULL);
90  if (ret < 0)
91  return ret;
92  *got_sub_ptr = sub->num_rects > 0;
93  return avpkt->size;
94 }
95 
97  .name = "webvtt",
98  .long_name = NULL_IF_CONFIG_SMALL("WebVTT subtitle"),
99  .type = AVMEDIA_TYPE_SUBTITLE,
100  .id = AV_CODEC_ID_WEBVTT,
101  .decode = webvtt_decode_frame,
103 };