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175 lines
5.5 KiB
175 lines
5.5 KiB
4 years ago
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/*
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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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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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" xmlns=\"http://www.w3.org/ns/ttml\"\n"
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" xmlns:ttm=\"http://www.w3.org/ns/ttml#metadata\"\n"
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" xmlns:tts=\"http://www.w3.org/ns/ttml#styling\"\n"
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" xml:lang=\"%s\">\n"
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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_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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avio_printf(pb, ttml_header_text, printed_lang);
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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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