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textdec.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  * Raw subtitles decoder
24  */
25 
26 #include "avcodec.h"
27 #include "ass.h"
28 #include "libavutil/bprint.h"
29 #include "libavutil/opt.h"
30 
31 typedef struct {
32  AVClass *class;
33  const char *linebreaks;
35 } TextContext;
36 
37 #define OFFSET(x) offsetof(TextContext, x)
38 #define SD AV_OPT_FLAG_SUBTITLE_PARAM | AV_OPT_FLAG_DECODING_PARAM
39 static const AVOption options[] = {
40  { "keep_ass_markup", "Set if ASS tags must be escaped", OFFSET(keep_ass_markup), AV_OPT_TYPE_INT, {.i64=0}, 0, 1, .flags=SD },
41  { NULL }
42 };
43 
44 static int text_event_to_ass(const AVCodecContext *avctx, AVBPrint *buf,
45  const char *p, const char *p_end)
46 {
47  const TextContext *text = avctx->priv_data;
48 
49  for (; p < p_end && *p; p++) {
50 
51  /* forced custom line breaks, not accounted as "normal" EOL */
52  if (text->linebreaks && strchr(text->linebreaks, *p)) {
53  av_bprintf(buf, "\\N");
54 
55  /* standard ASS escaping so random characters don't get mis-interpreted
56  * as ASS */
57  } else if (!text->keep_ass_markup && strchr("{}\\", *p)) {
58  av_bprintf(buf, "\\%c", *p);
59 
60  /* some packets might end abruptly (no \0 at the end, like for example
61  * in some cases of demuxing from a classic video container), some
62  * might be terminated with \n or \r\n which we have to remove (for
63  * consistency with those who haven't), and we also have to deal with
64  * evil cases such as \r at the end of the buffer (and no \0 terminated
65  * character) */
66  } else if (p[0] == '\n') {
67  /* some stuff left so we can insert a line break */
68  if (p < p_end - 1)
69  av_bprintf(buf, "\\N");
70  } else if (p[0] == '\r' && p < p_end - 1 && p[1] == '\n') {
71  /* \r followed by a \n, we can skip it. We don't insert the \N yet
72  * because we don't know if it is followed by more text */
73  continue;
74 
75  /* finally, a sane character */
76  } else {
77  av_bprint_chars(buf, *p, 1);
78  }
79  }
80  av_bprintf(buf, "\r\n");
81  return 0;
82 }
83 
84 static int text_decode_frame(AVCodecContext *avctx, void *data,
85  int *got_sub_ptr, AVPacket *avpkt)
86 {
87  AVBPrint buf;
88  AVSubtitle *sub = data;
89  const char *ptr = avpkt->data;
90  const int ts_start = av_rescale_q(avpkt->pts, avctx->time_base, (AVRational){1,100});
91  const int ts_duration = avpkt->duration != -1 ?
92  av_rescale_q(avpkt->duration, avctx->time_base, (AVRational){1,100}) : -1;
93 
95  if (ptr && avpkt->size > 0 && *ptr &&
96  !text_event_to_ass(avctx, &buf, ptr, ptr + avpkt->size)) {
97  if (!av_bprint_is_complete(&buf)) {
98  av_bprint_finalize(&buf, NULL);
99  return AVERROR(ENOMEM);
100  }
101  ff_ass_add_rect(sub, buf.str, ts_start, ts_duration, 0);
102  }
103  *got_sub_ptr = sub->num_rects > 0;
104  av_bprint_finalize(&buf, NULL);
105  return avpkt->size;
106 }
107 
108 #define DECLARE_CLASS(decname) static const AVClass decname ## _decoder_class = { \
109  .class_name = #decname " decoder", \
110  .item_name = av_default_item_name, \
111  .option = decname ## _options, \
112  .version = LIBAVUTIL_VERSION_INT, \
113 }
114 
115 #if CONFIG_TEXT_DECODER
116 #define text_options options
117 DECLARE_CLASS(text);
118 
119 AVCodec ff_text_decoder = {
120  .name = "text",
121  .priv_data_size = sizeof(TextContext),
122  .long_name = NULL_IF_CONFIG_SMALL("Raw text subtitle"),
123  .type = AVMEDIA_TYPE_SUBTITLE,
124  .id = AV_CODEC_ID_TEXT,
125  .decode = text_decode_frame,
127  .priv_class = &text_decoder_class,
128 };
129 #endif
130 
131 #if CONFIG_VPLAYER_DECODER || CONFIG_PJS_DECODER || CONFIG_SUBVIEWER1_DECODER
132 
133 static int linebreak_init(AVCodecContext *avctx)
134 {
135  TextContext *text = avctx->priv_data;
136  text->linebreaks = "|";
137  return ff_ass_subtitle_header_default(avctx);
138 }
139 
140 #if CONFIG_VPLAYER_DECODER
141 #define vplayer_options options
142 DECLARE_CLASS(vplayer);
143 
144 AVCodec ff_vplayer_decoder = {
145  .name = "vplayer",
146  .priv_data_size = sizeof(TextContext),
147  .long_name = NULL_IF_CONFIG_SMALL("VPlayer subtitle"),
148  .type = AVMEDIA_TYPE_SUBTITLE,
149  .id = AV_CODEC_ID_VPLAYER,
150  .decode = text_decode_frame,
151  .init = linebreak_init,
152  .priv_class = &vplayer_decoder_class,
153 };
154 #endif
155 
156 #if CONFIG_PJS_DECODER
157 #define pjs_options options
158 DECLARE_CLASS(pjs);
159 
160 AVCodec ff_pjs_decoder = {
161  .name = "pjs",
162  .priv_data_size = sizeof(TextContext),
163  .long_name = NULL_IF_CONFIG_SMALL("PJS subtitle"),
164  .type = AVMEDIA_TYPE_SUBTITLE,
165  .id = AV_CODEC_ID_PJS,
166  .decode = text_decode_frame,
167  .init = linebreak_init,
168  .priv_class = &pjs_decoder_class,
169 };
170 #endif
171 
172 #if CONFIG_SUBVIEWER1_DECODER
173 #define subviewer1_options options
174 DECLARE_CLASS(subviewer1);
175 
176 AVCodec ff_subviewer1_decoder = {
177  .name = "subviewer1",
178  .priv_data_size = sizeof(TextContext),
179  .long_name = NULL_IF_CONFIG_SMALL("SubViewer1 subtitle"),
180  .type = AVMEDIA_TYPE_SUBTITLE,
182  .decode = text_decode_frame,
183  .init = linebreak_init,
184  .priv_class = &subviewer1_decoder_class,
185 };
186 #endif
187 
188 #endif /* text subtitles with '|' line break */