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ffmpeg/libavformat/ttmlenc.c

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/*
* TTML subtitle muxer
* Copyright (c) 2020 24i
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file
* TTML subtitle muxer
* @see https://www.w3.org/TR/ttml1/
* @see https://www.w3.org/TR/ttml2/
* @see https://www.w3.org/TR/ttml-imsc/rec
*/
#include "libavutil/avstring.h"
#include "avformat.h"
#include "internal.h"
#include "ttmlenc.h"
#include "libavcodec/ttmlenc.h"
#include "libavutil/internal.h"
enum TTMLPacketType {
PACKET_TYPE_PARAGRAPH,
PACKET_TYPE_DOCUMENT,
};
struct TTMLHeaderParameters {
const char *tt_element_params;
const char *pre_body_elements;
};
typedef struct TTMLMuxContext {
enum TTMLPacketType input_type;
unsigned int document_written;
} TTMLMuxContext;
static const char ttml_header_text[] =
"<?xml version=\"1.0\" encoding=\"utf-8\"?>\n"
"<tt\n"
"%s"
" xml:lang=\"%s\">\n"
"%s"
" <body>\n"
" <div>\n";
static const char ttml_footer_text[] =
" </div>\n"
" </body>\n"
"</tt>\n";
static void ttml_write_time(AVIOContext *pb, const char tag[],
int64_t millisec)
{
int64_t sec, min, hour;
sec = millisec / 1000;
millisec -= 1000 * sec;
min = sec / 60;
sec -= 60 * min;
hour = min / 60;
min -= 60 * hour;
avio_printf(pb, "%s=\"%02"PRId64":%02"PRId64":%02"PRId64".%03"PRId64"\"",
tag, hour, min, sec, millisec);
}
static int ttml_set_header_values_from_extradata(
AVCodecParameters *par, struct TTMLHeaderParameters *header_params)
{
size_t additional_data_size =
par->extradata_size - TTMLENC_EXTRADATA_SIGNATURE_SIZE;
char *value =
(char *)par->extradata + TTMLENC_EXTRADATA_SIGNATURE_SIZE;
size_t value_size = av_strnlen(value, additional_data_size);
struct TTMLHeaderParameters local_params = { 0 };
if (!additional_data_size) {
// simple case, we don't have to go through local_params and just
// set default fall-back values (for old extradata format).
header_params->tt_element_params = TTML_DEFAULT_NAMESPACING;
header_params->pre_body_elements = "";
return 0;
}
if (value_size == additional_data_size ||
value[value_size] != '\0')
return AVERROR_INVALIDDATA;
local_params.tt_element_params = value;
additional_data_size -= value_size + 1;
value += value_size + 1;
if (!additional_data_size)
return AVERROR_INVALIDDATA;
value_size = av_strnlen(value, additional_data_size);
if (value_size == additional_data_size ||
value[value_size] != '\0')
return AVERROR_INVALIDDATA;
local_params.pre_body_elements = value;
*header_params = local_params;
return 0;
}
static int ttml_write_header(AVFormatContext *ctx)
{
TTMLMuxContext *ttml_ctx = ctx->priv_data;
ttml_ctx->document_written = 0;
if (ctx->nb_streams != 1 ||
ctx->streams[0]->codecpar->codec_id != AV_CODEC_ID_TTML) {
av_log(ctx, AV_LOG_ERROR, "Exactly one TTML stream is required!\n");
return AVERROR(EINVAL);
}
{
AVStream *st = ctx->streams[0];
AVIOContext *pb = ctx->pb;
AVDictionaryEntry *lang = av_dict_get(st->metadata, "language", NULL,
0);
const char *printed_lang = (lang && lang->value) ? lang->value : "";
ttml_ctx->input_type = ff_is_ttml_stream_paragraph_based(st->codecpar) ?
PACKET_TYPE_PARAGRAPH :
PACKET_TYPE_DOCUMENT;
avpriv_set_pts_info(st, 64, 1, 1000);
if (ttml_ctx->input_type == PACKET_TYPE_PARAGRAPH) {
struct TTMLHeaderParameters header_params;
int ret = ttml_set_header_values_from_extradata(
st->codecpar, &header_params);
if (ret < 0) {
av_log(ctx, AV_LOG_ERROR,
"Failed to parse TTML header values from extradata: "
"%s!\n", av_err2str(ret));
return ret;
}
avio_printf(pb, ttml_header_text,
header_params.tt_element_params,
printed_lang,
header_params.pre_body_elements);
}
}
return 0;
}
static int ttml_write_packet(AVFormatContext *ctx, AVPacket *pkt)
{
TTMLMuxContext *ttml_ctx = ctx->priv_data;
AVIOContext *pb = ctx->pb;
switch (ttml_ctx->input_type) {
case PACKET_TYPE_PARAGRAPH:
// write out a paragraph element with the given contents.
avio_printf(pb, " <p\n");
ttml_write_time(pb, " begin", pkt->pts);
avio_w8(pb, '\n');
ttml_write_time(pb, " end", pkt->pts + pkt->duration);
avio_printf(pb, ">");
avio_write(pb, pkt->data, pkt->size);
avio_printf(pb, "</p>\n");
break;
case PACKET_TYPE_DOCUMENT:
// dump the given document out as-is.
if (ttml_ctx->document_written) {
av_log(ctx, AV_LOG_ERROR,
"Attempting to write multiple TTML documents into a "
"single document! The XML specification forbids this "
"as there has to be a single root tag.\n");
return AVERROR(EINVAL);
}
avio_write(pb, pkt->data, pkt->size);
ttml_ctx->document_written = 1;
break;
default:
av_log(ctx, AV_LOG_ERROR,
"Internal error: invalid TTML input packet type: %d!\n",
ttml_ctx->input_type);
return AVERROR_BUG;
}
return 0;
}
static int ttml_write_trailer(AVFormatContext *ctx)
{
TTMLMuxContext *ttml_ctx = ctx->priv_data;
AVIOContext *pb = ctx->pb;
if (ttml_ctx->input_type == PACKET_TYPE_PARAGRAPH)
avio_printf(pb, ttml_footer_text);
return 0;
}
const AVOutputFormat ff_ttml_muxer = {
.name = "ttml",
.long_name = NULL_IF_CONFIG_SMALL("TTML subtitle"),
.extensions = "ttml",
.mime_type = "text/ttml",
.priv_data_size = sizeof(TTMLMuxContext),
.flags = AVFMT_GLOBALHEADER | AVFMT_VARIABLE_FPS |
AVFMT_TS_NONSTRICT,
.subtitle_codec = AV_CODEC_ID_TTML,
.write_header = ttml_write_header,
.write_packet = ttml_write_packet,
.write_trailer = ttml_write_trailer,
};
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