1 /*
2 * TTML subtitle muxer
3 * Copyright (c) 2020 24i
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22 /**
23 * @file
24 * TTML subtitle muxer
25 * @see https://www.w3.org/TR/ttml1/
26 * @see https://www.w3.org/TR/ttml2/
27 * @see https://www.w3.org/TR/ttml-imsc/rec
28 */
29
30 #include "libavutil/avstring.h"
31 #include "avformat.h"
32 #include "internal.h"
33 #include "ttmlenc.h"
34 #include "libavcodec/ttmlenc.h"
35 #include "libavutil/internal.h"
36
37 enum TTMLPacketType {
38 PACKET_TYPE_PARAGRAPH,
39 PACKET_TYPE_DOCUMENT,
40 };
41
42 struct TTMLHeaderParameters {
43 const char *tt_element_params;
44 const char *pre_body_elements;
45 };
46
47 typedef struct TTMLMuxContext {
48 enum TTMLPacketType input_type;
49 unsigned int document_written;
50 } TTMLMuxContext;
51
52 static const char ttml_header_text[] =
53 "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n"
54 "<tt\n"
55 "%s"
56 " xml:lang=\"%s\">\n"
57 "%s"
58 " <body>\n"
59 " <div>\n";
60
61 static const char ttml_footer_text[] =
62 " </div>\n"
63 " </body>\n"
64 "</tt>\n";
65
ttml_write_time(AVIOContext * pb,const char tag[],int64_t millisec)66 static void ttml_write_time(AVIOContext *pb, const char tag[],
67 int64_t millisec)
68 {
69 int64_t sec, min, hour;
70 sec = millisec / 1000;
71 millisec -= 1000 * sec;
72 min = sec / 60;
73 sec -= 60 * min;
74 hour = min / 60;
75 min -= 60 * hour;
76
77 avio_printf(pb, "%s=\"%02"PRId64":%02"PRId64":%02"PRId64".%03"PRId64"\"",
78 tag, hour, min, sec, millisec);
79 }
80
ttml_set_header_values_from_extradata(AVCodecParameters * par,struct TTMLHeaderParameters * header_params)81 static int ttml_set_header_values_from_extradata(
82 AVCodecParameters *par, struct TTMLHeaderParameters *header_params)
83 {
84 size_t additional_data_size =
85 par->extradata_size - TTMLENC_EXTRADATA_SIGNATURE_SIZE;
86 char *value =
87 (char *)par->extradata + TTMLENC_EXTRADATA_SIGNATURE_SIZE;
88 size_t value_size = av_strnlen(value, additional_data_size);
89 struct TTMLHeaderParameters local_params = { 0 };
90
91 if (!additional_data_size) {
92 // simple case, we don't have to go through local_params and just
93 // set default fall-back values (for old extradata format).
94 header_params->tt_element_params = ttml_default_namespacing;
95 header_params->pre_body_elements = "";
96
97 return 0;
98 }
99
100 if (value_size == additional_data_size ||
101 value[value_size] != '\0')
102 return AVERROR_INVALIDDATA;
103
104 local_params.tt_element_params = value;
105
106 additional_data_size -= value_size + 1;
107 value += value_size + 1;
108 if (!additional_data_size)
109 return AVERROR_INVALIDDATA;
110
111 value_size = av_strnlen(value, additional_data_size);
112 if (value_size == additional_data_size ||
113 value[value_size] != '\0')
114 return AVERROR_INVALIDDATA;
115
116 local_params.pre_body_elements = value;
117
118 *header_params = local_params;
119
120 return 0;
121 }
122
ttml_write_header(AVFormatContext * ctx)123 static int ttml_write_header(AVFormatContext *ctx)
124 {
125 TTMLMuxContext *ttml_ctx = ctx->priv_data;
126 ttml_ctx->document_written = 0;
127
128 if (ctx->nb_streams != 1 ||
129 ctx->streams[0]->codecpar->codec_id != AV_CODEC_ID_TTML) {
130 av_log(ctx, AV_LOG_ERROR, "Exactly one TTML stream is required!\n");
131 return AVERROR(EINVAL);
132 }
133
134 {
135 AVStream *st = ctx->streams[0];
136 AVIOContext *pb = ctx->pb;
137
138 AVDictionaryEntry *lang = av_dict_get(st->metadata, "language", NULL,
139 0);
140 const char *printed_lang = (lang && lang->value) ? lang->value : "";
141
142 ttml_ctx->input_type = ff_is_ttml_stream_paragraph_based(st->codecpar) ?
143 PACKET_TYPE_PARAGRAPH :
144 PACKET_TYPE_DOCUMENT;
145
146 avpriv_set_pts_info(st, 64, 1, 1000);
147
148 if (ttml_ctx->input_type == PACKET_TYPE_PARAGRAPH) {
149 struct TTMLHeaderParameters header_params;
150 int ret = ttml_set_header_values_from_extradata(
151 st->codecpar, &header_params);
152 if (ret < 0) {
153 av_log(ctx, AV_LOG_ERROR,
154 "Failed to parse TTML header values from extradata: "
155 "%s!\n", av_err2str(ret));
156 return ret;
157 }
158
159 avio_printf(pb, ttml_header_text,
160 header_params.tt_element_params,
161 printed_lang,
162 header_params.pre_body_elements);
163 }
164 }
165
166 return 0;
167 }
168
ttml_write_packet(AVFormatContext * ctx,AVPacket * pkt)169 static int ttml_write_packet(AVFormatContext *ctx, AVPacket *pkt)
170 {
171 TTMLMuxContext *ttml_ctx = ctx->priv_data;
172 AVIOContext *pb = ctx->pb;
173
174 switch (ttml_ctx->input_type) {
175 case PACKET_TYPE_PARAGRAPH:
176 // write out a paragraph element with the given contents.
177 avio_printf(pb, " <p\n");
178 ttml_write_time(pb, " begin", pkt->pts);
179 avio_w8(pb, '\n');
180 ttml_write_time(pb, " end", pkt->pts + pkt->duration);
181 avio_printf(pb, ">");
182 avio_write(pb, pkt->data, pkt->size);
183 avio_printf(pb, "</p>\n");
184 break;
185 case PACKET_TYPE_DOCUMENT:
186 // dump the given document out as-is.
187 if (ttml_ctx->document_written) {
188 av_log(ctx, AV_LOG_ERROR,
189 "Attempting to write multiple TTML documents into a "
190 "single document! The XML specification forbids this "
191 "as there has to be a single root tag.\n");
192 return AVERROR(EINVAL);
193 }
194 avio_write(pb, pkt->data, pkt->size);
195 ttml_ctx->document_written = 1;
196 break;
197 default:
198 av_log(ctx, AV_LOG_ERROR,
199 "Internal error: invalid TTML input packet type: %d!\n",
200 ttml_ctx->input_type);
201 return AVERROR_BUG;
202 }
203
204 return 0;
205 }
206
ttml_write_trailer(AVFormatContext * ctx)207 static int ttml_write_trailer(AVFormatContext *ctx)
208 {
209 TTMLMuxContext *ttml_ctx = ctx->priv_data;
210 AVIOContext *pb = ctx->pb;
211
212 if (ttml_ctx->input_type == PACKET_TYPE_PARAGRAPH)
213 avio_printf(pb, ttml_footer_text);
214
215 return 0;
216 }
217
218 const AVOutputFormat ff_ttml_muxer = {
219 .name = "ttml",
220 .long_name = NULL_IF_CONFIG_SMALL("TTML subtitle"),
221 .extensions = "ttml",
222 .mime_type = "text/ttml",
223 .priv_data_size = sizeof(TTMLMuxContext),
224 .flags = AVFMT_GLOBALHEADER | AVFMT_VARIABLE_FPS |
225 AVFMT_TS_NONSTRICT,
226 .subtitle_codec = AV_CODEC_ID_TTML,
227 .write_header = ttml_write_header,
228 .write_packet = ttml_write_packet,
229 .write_trailer = ttml_write_trailer,
230 };
231