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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  {"&gt;", ">"}, {"&lt;", "<"},
41  {"&lrm;", ""}, {"&rlm;", ""}, // FIXME: properly honor bidi marks
42  {"&amp;", "&"}, {"&nbsp;", "\\h"},
43 };
44 
45 static int webvtt_event_to_ass(AVBPrint *buf, const char *p)
46 {
47  int i, again = 0, skip = 0;
48 
49  while (*p) {
50 
51  for (i = 0; i < FF_ARRAY_ELEMS(webvtt_tag_replace); i++) {
52  const char *from = webvtt_tag_replace[i].from;
53  const size_t len = strlen(from);
54  if (!strncmp(p, from, len)) {
55  av_bprintf(buf, "%s", webvtt_tag_replace[i].to);
56  p += len;
57  again = 1;
58  break;
59  }
60  }
61  if (!*p)
62  break;
63 
64  if (again) {
65  again = 0;
66  skip = 0;
67  continue;
68  }
69  if (*p == '<')
70  skip = 1;
71  else if (*p == '>')
72  skip = 0;
73  else if (p[0] == '\n' && p[1])
74  av_bprintf(buf, "\\N");
75  else if (!skip && *p != '\r')
76  av_bprint_chars(buf, *p, 1);
77  p++;
78  }
79  return 0;
80 }
81 
83  void *data, int *got_sub_ptr, AVPacket *avpkt)
84 {
85  int ret = 0;
86  AVSubtitle *sub = data;
87  const char *ptr = avpkt->data;
89  AVBPrint buf;
90 
92  if (ptr && avpkt->size > 0 && !webvtt_event_to_ass(&buf, ptr))
93  ret = ff_ass_add_rect(sub, buf.str, s->readorder++, 0, NULL, NULL);
94  av_bprint_finalize(&buf, NULL);
95  if (ret < 0)
96  return ret;
97  *got_sub_ptr = sub->num_rects > 0;
98  return avpkt->size;
99 }
100 
102  .name = "webvtt",
103  .long_name = NULL_IF_CONFIG_SMALL("WebVTT subtitle"),
104  .type = AVMEDIA_TYPE_SUBTITLE,
105  .id = AV_CODEC_ID_WEBVTT,
106  .decode = webvtt_decode_frame,
108  .flush = ff_ass_decoder_flush,
109  .priv_data_size = sizeof(FFASSDecoderContext),
110 };
#define NULL
Definition: coverity.c:32
const char * s
Definition: avisynth_c.h:631
void av_bprintf(AVBPrint *buf, const char *fmt,...)
Definition: bprint.c:94
ptrdiff_t const GLvoid * data
Definition: opengl_enc.c:101
int size
Definition: avcodec.h:1580
unsigned num_rects
Definition: avcodec.h:3901
int ff_ass_add_rect(AVSubtitle *sub, const char *dialog, int readorder, int layer, const char *style, const char *speaker)
Add an ASS dialog to a subtitle.
Definition: ass.c:101
AVCodec.
Definition: avcodec.h:3541
int av_bprint_finalize(AVBPrint *buf, char **ret_str)
Finalize a print buffer.
Definition: bprint.c:235
int ff_ass_subtitle_header_default(AVCodecContext *avctx)
Generate a suitable AVCodecContext.subtitle_header for SUBTITLE_ASS with default style.
Definition: ass.c:80
uint8_t * data
Definition: avcodec.h:1579
const char * to
Definition: webvttdec.c:34
#define AV_BPRINT_SIZE_UNLIMITED
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:176
void av_bprint_init(AVBPrint *buf, unsigned size_init, unsigned size_max)
Definition: bprint.c:69
const char * name
Name of the codec implementation.
Definition: avcodec.h:3548
static const struct @138 webvtt_tag_replace[]
static int webvtt_event_to_ass(AVBPrint *buf, const char *p)
Definition: webvttdec.c:45
#define FF_ARRAY_ELEMS(a)
Libavcodec external API header.
main external API structure.
Definition: avcodec.h:1648
void * buf
Definition: avisynth_c.h:553
void ff_ass_decoder_flush(AVCodecContext *avctx)
Helper to flush a text subtitles decoder making use of the FFASSDecoderContext.
Definition: ass.c:124
static int webvtt_decode_frame(AVCodecContext *avctx, void *data, int *got_sub_ptr, AVPacket *avpkt)
Definition: webvttdec.c:82
AVCodec ff_webvtt_decoder
Definition: webvttdec.c:101
const char * from
Definition: webvttdec.c:33
void * priv_data
Definition: avcodec.h:1690
int len
This structure stores compressed data.
Definition: avcodec.h:1556
void av_bprint_chars(AVBPrint *buf, char c, unsigned n)
Append char c n times to a print buffer.
Definition: bprint.c:140