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This way the encoder may pass on the following values to the muxer: 1) Additional root "tt" element attributes, such as the subtitle canvas reference size. 2) Anything before the body element of the document, such as regions in the head element, which can configure styles. Signed-off-by: Jan Ekström <jan.ekstrom@24i.com>
235 lines
7.3 KiB
C
235 lines
7.3 KiB
C
/*
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* TTML subtitle muxer
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* Copyright (c) 2020 24i
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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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* TTML subtitle muxer
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* @see https://www.w3.org/TR/ttml1/
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* @see https://www.w3.org/TR/ttml2/
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* @see https://www.w3.org/TR/ttml-imsc/rec
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*/
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#include "avformat.h"
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#include "internal.h"
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#include "libavcodec/ttmlenc.h"
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#include "libavutil/internal.h"
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enum TTMLPacketType {
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PACKET_TYPE_PARAGRAPH,
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PACKET_TYPE_DOCUMENT,
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};
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struct TTMLHeaderParameters {
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const char *tt_element_params;
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const char *pre_body_elements;
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};
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typedef struct TTMLMuxContext {
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enum TTMLPacketType input_type;
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unsigned int document_written;
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} TTMLMuxContext;
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static const char ttml_header_text[] =
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"<?xml version=\"1.0\" encoding=\"utf-8\"?>\n"
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"<tt\n"
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"%s"
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" xml:lang=\"%s\">\n"
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"%s"
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" <body>\n"
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" <div>\n";
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static const char ttml_footer_text[] =
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" </div>\n"
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" </body>\n"
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"</tt>\n";
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static void ttml_write_time(AVIOContext *pb, const char tag[],
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int64_t millisec)
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{
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int64_t sec, min, hour;
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sec = millisec / 1000;
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millisec -= 1000 * sec;
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min = sec / 60;
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sec -= 60 * min;
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hour = min / 60;
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min -= 60 * hour;
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avio_printf(pb, "%s=\"%02"PRId64":%02"PRId64":%02"PRId64".%03"PRId64"\"",
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tag, hour, min, sec, millisec);
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}
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static int ttml_set_header_values_from_extradata(
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AVCodecParameters *par, struct TTMLHeaderParameters *header_params)
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{
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size_t additional_data_size =
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par->extradata_size - TTMLENC_EXTRADATA_SIGNATURE_SIZE;
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char *value =
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(char *)par->extradata + TTMLENC_EXTRADATA_SIGNATURE_SIZE;
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size_t value_size = av_strnlen(value, additional_data_size);
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struct TTMLHeaderParameters local_params = { 0 };
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if (!additional_data_size) {
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// simple case, we don't have to go through local_params and just
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// set default fall-back values (for old extradata format).
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header_params->tt_element_params = ttml_default_namespacing;
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header_params->pre_body_elements = "";
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return 0;
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}
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if (value_size == additional_data_size ||
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value[value_size] != '\0')
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return AVERROR_INVALIDDATA;
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local_params.tt_element_params = value;
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additional_data_size -= value_size + 1;
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value += value_size + 1;
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if (!additional_data_size)
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return AVERROR_INVALIDDATA;
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value_size = av_strnlen(value, additional_data_size);
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if (value_size == additional_data_size ||
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value[value_size] != '\0')
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return AVERROR_INVALIDDATA;
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local_params.pre_body_elements = value;
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*header_params = local_params;
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return 0;
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}
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static int ttml_write_header(AVFormatContext *ctx)
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{
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TTMLMuxContext *ttml_ctx = ctx->priv_data;
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ttml_ctx->document_written = 0;
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if (ctx->nb_streams != 1 ||
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ctx->streams[0]->codecpar->codec_id != AV_CODEC_ID_TTML) {
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av_log(ctx, AV_LOG_ERROR, "Exactly one TTML stream is required!\n");
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return AVERROR(EINVAL);
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}
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{
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AVStream *st = ctx->streams[0];
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AVIOContext *pb = ctx->pb;
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AVDictionaryEntry *lang = av_dict_get(st->metadata, "language", NULL,
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0);
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const char *printed_lang = (lang && lang->value) ? lang->value : "";
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// Not perfect, but decide whether the packet is a document or not
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// by the existence of the lavc ttmlenc extradata.
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ttml_ctx->input_type = (st->codecpar->extradata &&
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st->codecpar->extradata_size >= TTMLENC_EXTRADATA_SIGNATURE_SIZE &&
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!memcmp(st->codecpar->extradata,
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TTMLENC_EXTRADATA_SIGNATURE,
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TTMLENC_EXTRADATA_SIGNATURE_SIZE)) ?
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PACKET_TYPE_PARAGRAPH :
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PACKET_TYPE_DOCUMENT;
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avpriv_set_pts_info(st, 64, 1, 1000);
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if (ttml_ctx->input_type == PACKET_TYPE_PARAGRAPH) {
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struct TTMLHeaderParameters header_params;
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int ret = ttml_set_header_values_from_extradata(
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st->codecpar, &header_params);
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if (ret < 0) {
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av_log(ctx, AV_LOG_ERROR,
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"Failed to parse TTML header values from extradata: "
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"%s!\n", av_err2str(ret));
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return ret;
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}
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avio_printf(pb, ttml_header_text,
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header_params.tt_element_params,
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printed_lang,
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header_params.pre_body_elements);
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}
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}
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return 0;
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}
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static int ttml_write_packet(AVFormatContext *ctx, AVPacket *pkt)
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{
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TTMLMuxContext *ttml_ctx = ctx->priv_data;
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AVIOContext *pb = ctx->pb;
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switch (ttml_ctx->input_type) {
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case PACKET_TYPE_PARAGRAPH:
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// write out a paragraph element with the given contents.
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avio_printf(pb, " <p\n");
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ttml_write_time(pb, " begin", pkt->pts);
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avio_w8(pb, '\n');
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ttml_write_time(pb, " end", pkt->pts + pkt->duration);
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avio_printf(pb, ">");
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avio_write(pb, pkt->data, pkt->size);
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avio_printf(pb, "</p>\n");
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break;
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case PACKET_TYPE_DOCUMENT:
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// dump the given document out as-is.
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if (ttml_ctx->document_written) {
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av_log(ctx, AV_LOG_ERROR,
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"Attempting to write multiple TTML documents into a "
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"single document! The XML specification forbids this "
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"as there has to be a single root tag.\n");
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return AVERROR(EINVAL);
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}
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avio_write(pb, pkt->data, pkt->size);
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ttml_ctx->document_written = 1;
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break;
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default:
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av_log(ctx, AV_LOG_ERROR,
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"Internal error: invalid TTML input packet type: %d!\n",
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ttml_ctx->input_type);
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return AVERROR_BUG;
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}
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return 0;
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}
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static int ttml_write_trailer(AVFormatContext *ctx)
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{
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TTMLMuxContext *ttml_ctx = ctx->priv_data;
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AVIOContext *pb = ctx->pb;
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if (ttml_ctx->input_type == PACKET_TYPE_PARAGRAPH)
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avio_printf(pb, ttml_footer_text);
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return 0;
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}
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AVOutputFormat ff_ttml_muxer = {
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.name = "ttml",
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.long_name = NULL_IF_CONFIG_SMALL("TTML subtitle"),
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.extensions = "ttml",
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.mime_type = "text/ttml",
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.priv_data_size = sizeof(TTMLMuxContext),
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.flags = AVFMT_GLOBALHEADER | AVFMT_VARIABLE_FPS |
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AVFMT_TS_NONSTRICT,
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.subtitle_codec = AV_CODEC_ID_TTML,
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.write_header = ttml_write_header,
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.write_packet = ttml_write_packet,
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.write_trailer = ttml_write_trailer,
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};
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