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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. #include "libavutil/opt.h"
  33.  
  34. typedef struct {
  35.     const AVClass *class;
  36.     FFDemuxSubtitlesQueue q;
  37.     int kind;
  38. } WebVTTContext;
  39.  
  40. static int webvtt_probe(AVProbeData *p)
  41. {
  42.     const uint8_t *ptr = p->buf;
  43.  
  44.     if (AV_RB24(ptr) == 0xEFBBBF)
  45.         ptr += 3;  /* skip UTF-8 BOM */
  46.     if (!strncmp(ptr, "WEBVTT", 6) &&
  47.         (!ptr[6] || strchr("\n\r\t ", ptr[6])))
  48.         return AVPROBE_SCORE_MAX;
  49.     return 0;
  50. }
  51.  
  52. static int64_t read_ts(const char *s)
  53. {
  54.     int hh, mm, ss, ms;
  55.     if (sscanf(s, "%u:%u:%u.%u", &hh, &mm, &ss, &ms) == 4) return (hh*3600LL + mm*60LL + ss) * 1000LL + ms;
  56.     if (sscanf(s,    "%u:%u.%u",      &mm, &ss, &ms) == 3) return (            mm*60LL + ss) * 1000LL + ms;
  57.     return AV_NOPTS_VALUE;
  58. }
  59.  
  60. static int webvtt_read_header(AVFormatContext *s)
  61. {
  62.     WebVTTContext *webvtt = s->priv_data;
  63.     AVBPrint header, cue;
  64.     int res = 0;
  65.     AVStream *st = avformat_new_stream(s, NULL);
  66.  
  67.     if (!st)
  68.         return AVERROR(ENOMEM);
  69.     avpriv_set_pts_info(st, 64, 1, 1000);
  70.     st->codec->codec_type = AVMEDIA_TYPE_SUBTITLE;
  71.     st->codec->codec_id   = AV_CODEC_ID_WEBVTT;
  72.     st->disposition |= webvtt->kind;
  73.  
  74.     av_bprint_init(&header, 0, AV_BPRINT_SIZE_UNLIMITED);
  75.     av_bprint_init(&cue,    0, AV_BPRINT_SIZE_UNLIMITED);
  76.  
  77.     for (;;) {
  78.         int i;
  79.         int64_t pos;
  80.         AVPacket *sub;
  81.         const char *p, *identifier, *settings;
  82.         int identifier_len, settings_len;
  83.         int64_t ts_start, ts_end;
  84.  
  85.         ff_subtitles_read_chunk(s->pb, &cue);
  86.  
  87.         if (!cue.len)
  88.             break;
  89.  
  90.         p = identifier = cue.str;
  91.         pos = avio_tell(s->pb);
  92.  
  93.         /* ignore header chunk */
  94.         if (!strncmp(p, "\xEF\xBB\xBFWEBVTT", 9) ||
  95.             !strncmp(p, "WEBVTT", 6))
  96.             continue;
  97.  
  98.         /* optional cue identifier (can be a number like in SRT or some kind of
  99.          * chaptering id) */
  100.         for (i = 0; p[i] && p[i] != '\n' && p[i] != '\r'; i++) {
  101.             if (!strncmp(p + i, "-->", 3)) {
  102.                 identifier = NULL;
  103.                 break;
  104.             }
  105.         }
  106.         if (!identifier)
  107.             identifier_len = 0;
  108.         else {
  109.             identifier_len = strcspn(p, "\r\n");
  110.             p += identifier_len;
  111.             if (*p == '\r')
  112.                 p++;
  113.             if (*p == '\n')
  114.                 p++;
  115.         }
  116.  
  117.         /* cue timestamps */
  118.         if ((ts_start = read_ts(p)) == AV_NOPTS_VALUE)
  119.             break;
  120.         if (!(p = strstr(p, "-->")))
  121.             break;
  122.         p += 3;
  123.         do p++; while (*p == ' ' || *p == '\t');
  124.         if ((ts_end = read_ts(p)) == AV_NOPTS_VALUE)
  125.             break;
  126.  
  127.         /* optional cue settings */
  128.         p += strcspn(p, "\n\t ");
  129.         while (*p == '\t' || *p == ' ')
  130.             p++;
  131.         settings = p;
  132.         settings_len = strcspn(p, "\r\n");
  133.         p += settings_len;
  134.         if (*p == '\r')
  135.             p++;
  136.         if (*p == '\n')
  137.             p++;
  138.  
  139.         /* create packet */
  140.         sub = ff_subtitles_queue_insert(&webvtt->q, p, strlen(p), 0);
  141.         if (!sub) {
  142.             res = AVERROR(ENOMEM);
  143.             goto end;
  144.         }
  145.         sub->pos = pos;
  146.         sub->pts = ts_start;
  147.         sub->duration = ts_end - ts_start;
  148.  
  149. #define SET_SIDE_DATA(name, type) do {                                  \
  150.     if (name##_len) {                                                   \
  151.         uint8_t *buf = av_packet_new_side_data(sub, type, name##_len);  \
  152.         if (!buf) {                                                     \
  153.             res = AVERROR(ENOMEM);                                      \
  154.             goto end;                                                   \
  155.         }                                                               \
  156.         memcpy(buf, name, name##_len);                                  \
  157.     }                                                                   \
  158. } while (0)
  159.  
  160.         SET_SIDE_DATA(identifier, AV_PKT_DATA_WEBVTT_IDENTIFIER);
  161.         SET_SIDE_DATA(settings,   AV_PKT_DATA_WEBVTT_SETTINGS);
  162.     }
  163.  
  164.     ff_subtitles_queue_finalize(&webvtt->q);
  165.  
  166. end:
  167.     av_bprint_finalize(&cue,    NULL);
  168.     av_bprint_finalize(&header, NULL);
  169.     return res;
  170. }
  171.  
  172. static int webvtt_read_packet(AVFormatContext *s, AVPacket *pkt)
  173. {
  174.     WebVTTContext *webvtt = s->priv_data;
  175.     return ff_subtitles_queue_read_packet(&webvtt->q, pkt);
  176. }
  177.  
  178. static int webvtt_read_seek(AVFormatContext *s, int stream_index,
  179.                             int64_t min_ts, int64_t ts, int64_t max_ts, int flags)
  180. {
  181.     WebVTTContext *webvtt = s->priv_data;
  182.     return ff_subtitles_queue_seek(&webvtt->q, s, stream_index,
  183.                                    min_ts, ts, max_ts, flags);
  184. }
  185.  
  186. static int webvtt_read_close(AVFormatContext *s)
  187. {
  188.     WebVTTContext *webvtt = s->priv_data;
  189.     ff_subtitles_queue_clean(&webvtt->q);
  190.     return 0;
  191. }
  192.  
  193. #define OFFSET(x) offsetof(WebVTTContext, x)
  194. #define KIND_FLAGS AV_OPT_FLAG_SUBTITLE_PARAM
  195.  
  196. static const AVOption options[] = {
  197.     { "kind", "Set kind of WebVTT track", OFFSET(kind), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, KIND_FLAGS, "webvtt_kind" },
  198.         { "subtitles",    "WebVTT subtitles kind",    0, AV_OPT_TYPE_CONST, { .i64 = 0 },                           INT_MIN, INT_MAX, 0, "webvtt_kind" },
  199.         { "captions",     "WebVTT captions kind",     0, AV_OPT_TYPE_CONST, { .i64 = AV_DISPOSITION_CAPTIONS },     INT_MIN, INT_MAX, 0, "webvtt_kind" },
  200.         { "descriptions", "WebVTT descriptions kind", 0, AV_OPT_TYPE_CONST, { .i64 = AV_DISPOSITION_DESCRIPTIONS }, INT_MIN, INT_MAX, 0, "webvtt_kind" },
  201.         { "metadata",     "WebVTT metadata kind",     0, AV_OPT_TYPE_CONST, { .i64 = AV_DISPOSITION_METADATA },     INT_MIN, INT_MAX, 0, "webvtt_kind" },
  202.     { NULL }
  203. };
  204.  
  205. static const AVClass webvtt_demuxer_class = {
  206.     .class_name  = "WebVTT demuxer",
  207.     .item_name   = av_default_item_name,
  208.     .option      = options,
  209.     .version     = LIBAVUTIL_VERSION_INT,
  210. };
  211.  
  212. AVInputFormat ff_webvtt_demuxer = {
  213.     .name           = "webvtt",
  214.     .long_name      = NULL_IF_CONFIG_SMALL("WebVTT subtitle"),
  215.     .priv_data_size = sizeof(WebVTTContext),
  216.     .read_probe     = webvtt_probe,
  217.     .read_header    = webvtt_read_header,
  218.     .read_packet    = webvtt_read_packet,
  219.     .read_seek2     = webvtt_read_seek,
  220.     .read_close     = webvtt_read_close,
  221.     .extensions     = "vtt",
  222.     .priv_class     = &webvtt_demuxer_class,
  223. };
  224.