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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.  
  74. static int webvtt_decode_frame(AVCodecContext *avctx,
  75.                                void *data, int *got_sub_ptr, AVPacket *avpkt)
  76. {
  77.     AVSubtitle *sub = data;
  78.     const char *ptr = avpkt->data;
  79.     AVBPrint buf;
  80.  
  81.     av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
  82.     if (ptr && avpkt->size > 0 && !webvtt_event_to_ass(&buf, ptr)) {
  83.         int ts_start     = av_rescale_q(avpkt->pts, avctx->time_base, (AVRational){1,100});
  84.         int ts_duration  = avpkt->duration != -1 ?
  85.                            av_rescale_q(avpkt->duration, avctx->time_base, (AVRational){1,100}) : -1;
  86.         ff_ass_add_rect(sub, buf.str, ts_start, ts_duration, 0);
  87.     }
  88.     *got_sub_ptr = sub->num_rects > 0;
  89.     av_bprint_finalize(&buf, NULL);
  90.     return avpkt->size;
  91. }
  92.  
  93. AVCodec ff_webvtt_decoder = {
  94.     .name           = "webvtt",
  95.     .long_name      = NULL_IF_CONFIG_SMALL("WebVTT subtitle"),
  96.     .type           = AVMEDIA_TYPE_SUBTITLE,
  97.     .id             = AV_CODEC_ID_WEBVTT,
  98.     .decode         = webvtt_decode_frame,
  99.     .init           = ff_ass_subtitle_header_default,
  100. };
  101.