FFmpeg coverage

Directory: ../../../ffmpeg/
File: src/libavcodec/ttmlenc.c
Date: 2025-10-27 14:11:36
Exec Total Coverage
Lines: 130 178 73.0%
Functions: 11 11 100.0%
Branches: 31 68 45.6%
Line Branch Exec Source
1 /*
2 * TTML subtitle encoder
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 encoder
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 "avcodec.h"
31 #include "codec_internal.h"
32 #include "libavutil/bprint.h"
33 #include "libavutil/internal.h"
34 #include "libavutil/mem.h"
35 #include "ass_split.h"
36 #include "ttmlenc.h"
37
38 typedef struct {
39 AVCodecContext *avctx;
40 ASSSplitContext *ass_ctx;
41 AVBPrint buffer;
42 } TTMLContext;
43
44 510 static void ttml_text_cb(void *priv, const char *text, int len)
45 {
46 510 TTMLContext *s = priv;
47 AVBPrint cur_line;
48 510 AVBPrint *buffer = &s->buffer;
49
50 510 av_bprint_init(&cur_line, len, AV_BPRINT_SIZE_UNLIMITED);
51
52 510 av_bprint_append_data(&cur_line, text, len);
53
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 510 if (!av_bprint_is_complete(&cur_line)) {
54 ✗ av_log(s->avctx, AV_LOG_ERROR,
55 "Failed to move the current subtitle dialog to AVBPrint!\n");
56 ✗ av_bprint_finalize(&cur_line, NULL);
57 ✗ return;
58 }
59
60
61 510 av_bprint_escape(buffer, cur_line.str, NULL, AV_ESCAPE_MODE_XML,
62 0);
63
64 510 av_bprint_finalize(&cur_line, NULL);
65 }
66
67 325 static void ttml_new_line_cb(void *priv, int forced)
68 {
69 325 TTMLContext *s = priv;
70
71 325 av_bprintf(&s->buffer, "<br/>");
72 325 }
73
74 static const ASSCodesCallbacks ttml_callbacks = {
75 .text = ttml_text_cb,
76 .new_line = ttml_new_line_cb,
77 };
78
79 185 static int ttml_encode_frame(AVCodecContext *avctx, uint8_t *buf,
80 int bufsize, const AVSubtitle *sub)
81 {
82 185 TTMLContext *s = avctx->priv_data;
83 ASSDialog *dialog;
84 int i;
85
86 185 av_bprint_init_for_buffer(&s->buffer, buf, bufsize);
87
88
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 370 for (i=0; i<sub->num_rects; i++) {
89 185 const char *ass = sub->rects[i]->ass;
90 int ret;
91
92
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 185 if (sub->rects[i]->type != SUBTITLE_ASS) {
93 ✗ av_log(avctx, AV_LOG_ERROR, "Only SUBTITLE_ASS type supported.\n");
94 ✗ return AVERROR(EINVAL);
95 }
96
97 185 dialog = ff_ass_split_dialog(s->ass_ctx, ass);
98
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 185 if (!dialog)
99 ✗ return AVERROR(ENOMEM);
100
101
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 185 if (dialog->style) {
102 185 av_bprintf(&s->buffer, "<span region=\"");
103 185 av_bprint_escape(&s->buffer, dialog->style, NULL,
104 AV_ESCAPE_MODE_XML,
105 AV_ESCAPE_FLAG_XML_DOUBLE_QUOTES);
106 185 av_bprintf(&s->buffer, "\">");
107 }
108
109 185 ret = ff_ass_split_override_codes(&ttml_callbacks, s, dialog->text);
110
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 185 if (ret < 0) {
111 ✗ int log_level = (ret != AVERROR_INVALIDDATA ||
112 ✗ avctx->err_recognition & AV_EF_EXPLODE) ?
113 ✗ AV_LOG_ERROR : AV_LOG_WARNING;
114 ✗ av_log(avctx, log_level,
115 "Splitting received ASS dialog text %s failed: %s\n",
116 ✗ dialog->text,
117 ✗ av_err2str(ret));
118
119 ✗ if (log_level == AV_LOG_ERROR) {
120 ✗ ff_ass_free_dialog(&dialog);
121 ✗ return ret;
122 }
123 }
124
125
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 185 if (dialog->style)
126 185 av_bprintf(&s->buffer, "</span>");
127
128 185 ff_ass_free_dialog(&dialog);
129 }
130
131
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 185 if (!s->buffer.len)
132 ✗ return 0;
133
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 185 if (!av_bprint_is_complete(&s->buffer)) {
134 ✗ av_log(avctx, AV_LOG_ERROR, "Buffer too small for TTML event.\n");
135 ✗ return AVERROR_BUFFER_TOO_SMALL;
136 }
137
138 185 return s->buffer.len;
139 }
140
141 5 static av_cold int ttml_encode_close(AVCodecContext *avctx)
142 {
143 5 TTMLContext *s = avctx->priv_data;
144
145 5 ff_ass_split_free(s->ass_ctx);
146
147 5 return 0;
148 }
149
150 5 static const char *ttml_get_display_alignment(int alignment)
151 {
152
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 5 switch (alignment) {
153 5 case 1:
154 case 2:
155 case 3:
156 5 return "after";
157 ✗ case 4:
158 case 5:
159 case 6:
160 ✗ return "center";
161 ✗ case 7:
162 case 8:
163 case 9:
164 ✗ return "before";
165 ✗ default:
166 ✗ return NULL;
167 }
168 }
169
170 5 static const char *ttml_get_text_alignment(int alignment)
171 {
172
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 5 switch (alignment) {
173 ✗ case 1:
174 case 4:
175 case 7:
176 ✗ return "left";
177 5 case 2:
178 case 5:
179 case 8:
180 5 return "center";
181 ✗ case 3:
182 case 6:
183 case 9:
184 ✗ return "right";
185 ✗ default:
186 ✗ return NULL;
187 }
188 }
189
190 5 static void ttml_get_origin(ASSScriptInfo script_info, ASSStyle style,
191 int *origin_left, int *origin_top)
192 {
193 5 *origin_left = av_rescale(style.margin_l, 100, script_info.play_res_x);
194 5 *origin_top =
195 5 av_rescale((style.alignment >= 7) ? style.margin_v : 0,
196
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 5 100, script_info.play_res_y);
197 5 }
198
199 5 static void ttml_get_extent(ASSScriptInfo script_info, ASSStyle style,
200 int *width, int *height)
201 {
202 5 *width = av_rescale(script_info.play_res_x - style.margin_r,
203 5 100, script_info.play_res_x);
204 15 *height = av_rescale((style.alignment <= 3) ?
205 5 script_info.play_res_y - style.margin_v :
206 ✗ script_info.play_res_y,
207
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 5 100, script_info.play_res_y);
208 5 }
209
210 5 static int ttml_write_region(AVCodecContext *avctx, AVBPrint *buf,
211 ASSScriptInfo script_info, ASSStyle style)
212 {
213 5 const char *display_alignment = NULL;
214 5 const char *text_alignment = NULL;
215 5 int origin_left = 0;
216 5 int origin_top = 0;
217 5 int width = 0;
218 5 int height = 0;
219
220
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 5 if (!style.name) {
221 ✗ av_log(avctx, AV_LOG_ERROR, "Subtitle style name not set!\n");
222 ✗ return AVERROR_INVALIDDATA;
223 }
224
225
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 5 if (style.font_size < 0) {
226 ✗ av_log(avctx, AV_LOG_ERROR, "Invalid font size for TTML: %d!\n",
227 style.font_size);
228 ✗ return AVERROR_INVALIDDATA;
229 }
230
231
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 5 if (style.margin_l < 0 || style.margin_r < 0 || style.margin_v < 0) {
232 ✗ av_log(avctx, AV_LOG_ERROR,
233 "One or more negative margin values in subtitle style: "
234 "left: %d, right: %d, vertical: %d!\n",
235 style.margin_l, style.margin_r, style.margin_v);
236 ✗ return AVERROR_INVALIDDATA;
237 }
238
239 5 display_alignment = ttml_get_display_alignment(style.alignment);
240 5 text_alignment = ttml_get_text_alignment(style.alignment);
241
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 5 if (!display_alignment || !text_alignment) {
242 ✗ av_log(avctx, AV_LOG_ERROR,
243 "Failed to convert ASS style alignment %d of style %s to "
244 "TTML display and text alignment!\n",
245 style.alignment,
246 style.name);
247 ✗ return AVERROR_INVALIDDATA;
248 }
249
250 5 ttml_get_origin(script_info, style, &origin_left, &origin_top);
251 5 ttml_get_extent(script_info, style, &width, &height);
252
253 5 av_bprintf(buf, " <region xml:id=\"");
254 5 av_bprint_escape(buf, style.name, NULL, AV_ESCAPE_MODE_XML,
255 AV_ESCAPE_FLAG_XML_DOUBLE_QUOTES);
256 5 av_bprintf(buf, "\"\n");
257
258 5 av_bprintf(buf, " tts:origin=\"%d%% %d%%\"\n",
259 origin_left, origin_top);
260 5 av_bprintf(buf, " tts:extent=\"%d%% %d%%\"\n",
261 width, height);
262
263 5 av_bprintf(buf, " tts:displayAlign=\"");
264 5 av_bprint_escape(buf, display_alignment, NULL, AV_ESCAPE_MODE_XML,
265 AV_ESCAPE_FLAG_XML_DOUBLE_QUOTES);
266 5 av_bprintf(buf, "\"\n");
267
268 5 av_bprintf(buf, " tts:textAlign=\"");
269 5 av_bprint_escape(buf, text_alignment, NULL, AV_ESCAPE_MODE_XML,
270 AV_ESCAPE_FLAG_XML_DOUBLE_QUOTES);
271 5 av_bprintf(buf, "\"\n");
272
273 // if we set cell resolution to our script reference resolution,
274 // then a single line is a single "point" on our canvas. Thus, by setting
275 // our font size to font size in cells, we should gain a similar enough
276 // scale without resorting to explicit pixel based font sizing, which is
277 // frowned upon in the TTML community.
278 5 av_bprintf(buf, " tts:fontSize=\"%dc\"\n",
279 style.font_size);
280
281
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 5 if (style.font_name) {
282 5 av_bprintf(buf, " tts:fontFamily=\"");
283 5 av_bprint_escape(buf, style.font_name, NULL, AV_ESCAPE_MODE_XML,
284 AV_ESCAPE_FLAG_XML_DOUBLE_QUOTES);
285 5 av_bprintf(buf, "\"\n");
286 }
287
288 5 av_bprintf(buf, " tts:overflow=\"visible\" />\n");
289
290 5 return 0;
291 }
292
293 5 static int ttml_write_header_content(AVCodecContext *avctx)
294 {
295 5 TTMLContext *s = avctx->priv_data;
296 5 ASS *ass = (ASS *)s->ass_ctx;
297 5 ASSScriptInfo script_info = ass->script_info;
298 5 const size_t base_extradata_size = TTMLENC_EXTRADATA_SIGNATURE_SIZE + 1 +
299 AV_INPUT_BUFFER_PADDING_SIZE;
300 5 size_t additional_extradata_size = 0;
301 int ret;
302
303
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 5 if (script_info.play_res_x <= 0 || script_info.play_res_y <= 0) {
304 ✗ av_log(avctx, AV_LOG_ERROR,
305 "Invalid subtitle reference resolution %dx%d!\n",
306 script_info.play_res_x, script_info.play_res_y);
307 ✗ return AVERROR_INVALIDDATA;
308 }
309
310 5 av_bprint_init(&s->buffer, 0, INT_MAX - base_extradata_size);
311
312 // write the first string in extradata, attributes in the base "tt" element.
313 5 av_bprintf(&s->buffer, TTML_DEFAULT_NAMESPACING);
314 // the cell resolution is in character cells, so not exactly 1:1 against
315 // a pixel based resolution, but as the tts:extent in the root
316 // "tt" element is frowned upon (and disallowed in the EBU-TT profile),
317 // we mimic the reference resolution by setting it as the cell resolution.
318 5 av_bprintf(&s->buffer, " ttp:cellResolution=\"%d %d\"\n",
319 script_info.play_res_x, script_info.play_res_y);
320 5 av_bprint_chars(&s->buffer, '\0', 1);
321
322 // write the second string in extradata, head element containing the styles
323 5 av_bprintf(&s->buffer, " <head>\n");
324 5 av_bprintf(&s->buffer, " <layout>\n");
325
326
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 10 for (int i = 0; i < ass->styles_count; i++) {
327 5 ret = ttml_write_region(avctx, &s->buffer, script_info,
328 5 ass->styles[i]);
329
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 5 if (ret < 0)
330 ✗ goto fail;
331 }
332
333 5 av_bprintf(&s->buffer, " </layout>\n");
334 5 av_bprintf(&s->buffer, " </head>\n");
335 5 av_bprint_chars(&s->buffer, '\0', 1);
336
337
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 5 if (!av_bprint_is_complete(&s->buffer)) {
338 ✗ ret = AVERROR(ENOMEM);
339 ✗ goto fail;
340 }
341
342 5 additional_extradata_size = s->buffer.len;
343
344
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 5 if (!(avctx->extradata =
345 5 av_mallocz(base_extradata_size + additional_extradata_size))) {
346 ✗ ret = AVERROR(ENOMEM);
347 ✗ goto fail;
348 }
349
350 5 avctx->extradata_size =
351 5 TTMLENC_EXTRADATA_SIGNATURE_SIZE + additional_extradata_size;
352 5 memcpy(avctx->extradata, TTMLENC_EXTRADATA_SIGNATURE,
353 TTMLENC_EXTRADATA_SIGNATURE_SIZE);
354
355 5 memcpy(avctx->extradata + TTMLENC_EXTRADATA_SIGNATURE_SIZE,
356 5 s->buffer.str, additional_extradata_size);
357
358 5 ret = 0;
359 5 fail:
360 5 av_bprint_finalize(&s->buffer, NULL);
361
362 5 return ret;
363 }
364
365 5 static av_cold int ttml_encode_init(AVCodecContext *avctx)
366 {
367 5 TTMLContext *s = avctx->priv_data;
368 5 int ret = AVERROR_BUG;
369 5 s->avctx = avctx;
370
371
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 5 if (!(s->ass_ctx = ff_ass_split(avctx->subtitle_header))) {
372 ✗ return AVERROR_INVALIDDATA;
373 }
374
375
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 5 if ((ret = ttml_write_header_content(avctx)) < 0) {
376 ✗ return ret;
377 }
378
379 5 return 0;
380 }
381
382 const FFCodec ff_ttml_encoder = {
383 .p.name = "ttml",
384 CODEC_LONG_NAME("TTML subtitle"),
385 .p.type = AVMEDIA_TYPE_SUBTITLE,
386 .p.id = AV_CODEC_ID_TTML,
387 .priv_data_size = sizeof(TTMLContext),
388 .init = ttml_encode_init,
389 FF_CODEC_ENCODE_SUB_CB(ttml_encode_frame),
390 .close = ttml_encode_close,
391 .caps_internal = FF_CODEC_CAP_INIT_CLEANUP,
392 };
393