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WebVTT subtitle tracks have four kinds. Certain downstream muxers (such as for WebM) need to know which WebVTT kind this is, in order to specify the codec id of the output track. A new private input option, "-kind", has been added to the WebVTT demuxer. It accepts as a value any of "subtitles" (the default), "captions", "descriptions", and "metadata". The kind option value is used to assign a value to the stream disposition flag, to which four new values have been added, corresponding the four WebVTT kinds. Signed-off-by: Matthew Heaney <matthewjheaney@google.com> Signed-off-by: Clément Bœsch <ubitux@gmail.com>
224 lines
7.2 KiB
C
224 lines
7.2 KiB
C
/*
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* Copyright (c) 2012 Clément Bœsch
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file
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* WebVTT subtitle demuxer
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* @see http://dev.w3.org/html5/webvtt/
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*/
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#include "avformat.h"
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#include "internal.h"
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#include "subtitles.h"
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#include "libavutil/bprint.h"
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#include "libavutil/intreadwrite.h"
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#include "libavutil/opt.h"
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typedef struct {
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const AVClass *class;
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FFDemuxSubtitlesQueue q;
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int kind;
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} WebVTTContext;
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static int webvtt_probe(AVProbeData *p)
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{
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const uint8_t *ptr = p->buf;
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if (AV_RB24(ptr) == 0xEFBBBF)
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ptr += 3; /* skip UTF-8 BOM */
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if (!strncmp(ptr, "WEBVTT", 6) &&
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(!ptr[6] || strchr("\n\r\t ", ptr[6])))
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return AVPROBE_SCORE_MAX;
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return 0;
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}
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static int64_t read_ts(const char *s)
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{
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int hh, mm, ss, ms;
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if (sscanf(s, "%u:%u:%u.%u", &hh, &mm, &ss, &ms) == 4) return (hh*3600LL + mm*60LL + ss) * 1000LL + ms;
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if (sscanf(s, "%u:%u.%u", &mm, &ss, &ms) == 3) return ( mm*60LL + ss) * 1000LL + ms;
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return AV_NOPTS_VALUE;
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}
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static int webvtt_read_header(AVFormatContext *s)
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{
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WebVTTContext *webvtt = s->priv_data;
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AVBPrint header, cue;
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int res = 0;
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AVStream *st = avformat_new_stream(s, NULL);
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if (!st)
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return AVERROR(ENOMEM);
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avpriv_set_pts_info(st, 64, 1, 1000);
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st->codec->codec_type = AVMEDIA_TYPE_SUBTITLE;
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st->codec->codec_id = AV_CODEC_ID_WEBVTT;
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st->disposition |= webvtt->kind;
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av_bprint_init(&header, 0, AV_BPRINT_SIZE_UNLIMITED);
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av_bprint_init(&cue, 0, AV_BPRINT_SIZE_UNLIMITED);
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for (;;) {
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int i;
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int64_t pos;
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AVPacket *sub;
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const char *p, *identifier, *settings;
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int identifier_len, settings_len;
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int64_t ts_start, ts_end;
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ff_subtitles_read_chunk(s->pb, &cue);
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if (!cue.len)
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break;
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p = identifier = cue.str;
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pos = avio_tell(s->pb);
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/* ignore header chunk */
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if (!strncmp(p, "\xEF\xBB\xBFWEBVTT", 9) ||
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!strncmp(p, "WEBVTT", 6))
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continue;
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/* optional cue identifier (can be a number like in SRT or some kind of
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* chaptering id) */
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for (i = 0; p[i] && p[i] != '\n' && p[i] != '\r'; i++) {
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if (!strncmp(p + i, "-->", 3)) {
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identifier = NULL;
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break;
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}
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}
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if (!identifier)
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identifier_len = 0;
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else {
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identifier_len = strcspn(p, "\r\n");
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p += identifier_len;
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if (*p == '\r')
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p++;
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if (*p == '\n')
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p++;
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}
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/* cue timestamps */
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if ((ts_start = read_ts(p)) == AV_NOPTS_VALUE)
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break;
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if (!(p = strstr(p, "-->")))
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break;
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p += 3;
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do p++; while (*p == ' ' || *p == '\t');
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if ((ts_end = read_ts(p)) == AV_NOPTS_VALUE)
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break;
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/* optional cue settings */
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p += strcspn(p, "\n\t ");
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while (*p == '\t' || *p == ' ')
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p++;
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settings = p;
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settings_len = strcspn(p, "\r\n");
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p += settings_len;
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if (*p == '\r')
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p++;
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if (*p == '\n')
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p++;
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/* create packet */
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sub = ff_subtitles_queue_insert(&webvtt->q, p, strlen(p), 0);
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if (!sub) {
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res = AVERROR(ENOMEM);
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goto end;
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}
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sub->pos = pos;
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sub->pts = ts_start;
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sub->duration = ts_end - ts_start;
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#define SET_SIDE_DATA(name, type) do { \
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if (name##_len) { \
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uint8_t *buf = av_packet_new_side_data(sub, type, name##_len); \
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if (!buf) { \
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res = AVERROR(ENOMEM); \
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goto end; \
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} \
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memcpy(buf, name, name##_len); \
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} \
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} while (0)
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SET_SIDE_DATA(identifier, AV_PKT_DATA_WEBVTT_IDENTIFIER);
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SET_SIDE_DATA(settings, AV_PKT_DATA_WEBVTT_SETTINGS);
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}
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ff_subtitles_queue_finalize(&webvtt->q);
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end:
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av_bprint_finalize(&cue, NULL);
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av_bprint_finalize(&header, NULL);
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return res;
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}
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static int webvtt_read_packet(AVFormatContext *s, AVPacket *pkt)
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{
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WebVTTContext *webvtt = s->priv_data;
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return ff_subtitles_queue_read_packet(&webvtt->q, pkt);
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}
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static int webvtt_read_seek(AVFormatContext *s, int stream_index,
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int64_t min_ts, int64_t ts, int64_t max_ts, int flags)
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{
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WebVTTContext *webvtt = s->priv_data;
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return ff_subtitles_queue_seek(&webvtt->q, s, stream_index,
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min_ts, ts, max_ts, flags);
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}
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static int webvtt_read_close(AVFormatContext *s)
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{
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WebVTTContext *webvtt = s->priv_data;
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ff_subtitles_queue_clean(&webvtt->q);
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return 0;
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}
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#define OFFSET(x) offsetof(WebVTTContext, x)
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#define KIND_FLAGS AV_OPT_FLAG_SUBTITLE_PARAM
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static const AVOption options[] = {
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{ "kind", "Set kind of WebVTT track", OFFSET(kind), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, KIND_FLAGS, "webvtt_kind" },
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{ "subtitles", "WebVTT subtitles kind", 0, AV_OPT_TYPE_CONST, { .i64 = 0 }, INT_MIN, INT_MAX, 0, "webvtt_kind" },
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{ "captions", "WebVTT captions kind", 0, AV_OPT_TYPE_CONST, { .i64 = AV_DISPOSITION_CAPTIONS }, INT_MIN, INT_MAX, 0, "webvtt_kind" },
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{ "descriptions", "WebVTT descriptions kind", 0, AV_OPT_TYPE_CONST, { .i64 = AV_DISPOSITION_DESCRIPTIONS }, INT_MIN, INT_MAX, 0, "webvtt_kind" },
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{ "metadata", "WebVTT metadata kind", 0, AV_OPT_TYPE_CONST, { .i64 = AV_DISPOSITION_METADATA }, INT_MIN, INT_MAX, 0, "webvtt_kind" },
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{ NULL }
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};
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static const AVClass webvtt_demuxer_class = {
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.class_name = "WebVTT demuxer",
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.item_name = av_default_item_name,
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.option = options,
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.version = LIBAVUTIL_VERSION_INT,
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};
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AVInputFormat ff_webvtt_demuxer = {
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.name = "webvtt",
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.long_name = NULL_IF_CONFIG_SMALL("WebVTT subtitle"),
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.priv_data_size = sizeof(WebVTTContext),
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.read_probe = webvtt_probe,
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.read_header = webvtt_read_header,
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.read_packet = webvtt_read_packet,
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.read_seek2 = webvtt_read_seek,
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.read_close = webvtt_read_close,
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.extensions = "vtt",
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.priv_class = &webvtt_demuxer_class,
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};
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