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path: root/libavcodec/webvttenc.c (plain)
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1/*
2 * WebVTT subtitle encoder
3 * Copyright (c) 2010 Aurelien Jacobs <aurel@gnuage.org>
4 * Copyright (c) 2014 Aman Gupta <ffmpeg@tmm1.net>
5 *
6 * This file is part of FFmpeg.
7 *
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23#include <stdarg.h>
24#include "avcodec.h"
25#include "libavutil/avstring.h"
26#include "libavutil/bprint.h"
27#include "ass_split.h"
28#include "ass.h"
29
30#define WEBVTT_STACK_SIZE 64
31typedef struct {
32 AVCodecContext *avctx;
33 ASSSplitContext *ass_ctx;
34 AVBPrint buffer;
35 unsigned timestamp_end;
36 int count;
37 char stack[WEBVTT_STACK_SIZE];
38 int stack_ptr;
39} WebVTTContext;
40
41#ifdef __GNUC__
42__attribute__ ((__format__ (__printf__, 2, 3)))
43#endif
44static void webvtt_print(WebVTTContext *s, const char *str, ...)
45{
46 va_list vargs;
47 va_start(vargs, str);
48 av_vbprintf(&s->buffer, str, vargs);
49 va_end(vargs);
50}
51
52static int webvtt_stack_push(WebVTTContext *s, const char c)
53{
54 if (s->stack_ptr >= WEBVTT_STACK_SIZE)
55 return -1;
56 s->stack[s->stack_ptr++] = c;
57 return 0;
58}
59
60static char webvtt_stack_pop(WebVTTContext *s)
61{
62 if (s->stack_ptr <= 0)
63 return 0;
64 return s->stack[--s->stack_ptr];
65}
66
67static int webvtt_stack_find(WebVTTContext *s, const char c)
68{
69 int i;
70 for (i = s->stack_ptr-1; i >= 0; i--)
71 if (s->stack[i] == c)
72 break;
73 return i;
74}
75
76static void webvtt_close_tag(WebVTTContext *s, char tag)
77{
78 webvtt_print(s, "</%c>", tag);
79}
80
81static void webvtt_stack_push_pop(WebVTTContext *s, const char c, int close)
82{
83 if (close) {
84 int i = c ? webvtt_stack_find(s, c) : 0;
85 if (i < 0)
86 return;
87 while (s->stack_ptr != i)
88 webvtt_close_tag(s, webvtt_stack_pop(s));
89 } else if (webvtt_stack_push(s, c) < 0)
90 av_log(s->avctx, AV_LOG_ERROR, "tag stack overflow\n");
91}
92
93static void webvtt_style_apply(WebVTTContext *s, const char *style)
94{
95 ASSStyle *st = ff_ass_style_get(s->ass_ctx, style);
96 if (st) {
97 if (st->bold != ASS_DEFAULT_BOLD) {
98 webvtt_print(s, "<b>");
99 webvtt_stack_push(s, 'b');
100 }
101 if (st->italic != ASS_DEFAULT_ITALIC) {
102 webvtt_print(s, "<i>");
103 webvtt_stack_push(s, 'i');
104 }
105 if (st->underline != ASS_DEFAULT_UNDERLINE) {
106 webvtt_print(s, "<u>");
107 webvtt_stack_push(s, 'u');
108 }
109 }
110}
111
112static void webvtt_text_cb(void *priv, const char *text, int len)
113{
114 WebVTTContext *s = priv;
115 av_bprint_append_data(&s->buffer, text, len);
116}
117
118static void webvtt_new_line_cb(void *priv, int forced)
119{
120 webvtt_print(priv, "\n");
121}
122
123static void webvtt_style_cb(void *priv, char style, int close)
124{
125 if (style == 's') // strikethrough unsupported
126 return;
127
128 webvtt_stack_push_pop(priv, style, close);
129 if (!close)
130 webvtt_print(priv, "<%c>", style);
131}
132
133static void webvtt_cancel_overrides_cb(void *priv, const char *style)
134{
135 webvtt_stack_push_pop(priv, 0, 1);
136 webvtt_style_apply(priv, style);
137}
138
139static void webvtt_end_cb(void *priv)
140{
141 webvtt_stack_push_pop(priv, 0, 1);
142}
143
144static const ASSCodesCallbacks webvtt_callbacks = {
145 .text = webvtt_text_cb,
146 .new_line = webvtt_new_line_cb,
147 .style = webvtt_style_cb,
148 .color = NULL,
149 .font_name = NULL,
150 .font_size = NULL,
151 .alignment = NULL,
152 .cancel_overrides = webvtt_cancel_overrides_cb,
153 .move = NULL,
154 .end = webvtt_end_cb,
155};
156
157static int webvtt_encode_frame(AVCodecContext *avctx,
158 unsigned char *buf, int bufsize, const AVSubtitle *sub)
159{
160 WebVTTContext *s = avctx->priv_data;
161 ASSDialog *dialog;
162 int i;
163
164 av_bprint_clear(&s->buffer);
165
166 for (i=0; i<sub->num_rects; i++) {
167 const char *ass = sub->rects[i]->ass;
168
169 if (sub->rects[i]->type != SUBTITLE_ASS) {
170 av_log(avctx, AV_LOG_ERROR, "Only SUBTITLE_ASS type supported.\n");
171 return AVERROR(ENOSYS);
172 }
173
174#if FF_API_ASS_TIMING
175 if (!strncmp(ass, "Dialogue: ", 10)) {
176 int num;
177 dialog = ff_ass_split_dialog(s->ass_ctx, ass, 0, &num);
178 // TODO reindent
179 for (; dialog && num--; dialog++) {
180 webvtt_style_apply(s, dialog->style);
181 ff_ass_split_override_codes(&webvtt_callbacks, s, dialog->text);
182 }
183 } else {
184#endif
185 dialog = ff_ass_split_dialog2(s->ass_ctx, ass);
186 if (!dialog)
187 return AVERROR(ENOMEM);
188 webvtt_style_apply(s, dialog->style);
189 ff_ass_split_override_codes(&webvtt_callbacks, s, dialog->text);
190 ff_ass_free_dialog(&dialog);
191#if FF_API_ASS_TIMING
192 }
193#endif
194 }
195
196 if (!av_bprint_is_complete(&s->buffer))
197 return AVERROR(ENOMEM);
198 if (!s->buffer.len)
199 return 0;
200
201 if (s->buffer.len > bufsize) {
202 av_log(avctx, AV_LOG_ERROR, "Buffer too small for ASS event.\n");
203 return -1;
204 }
205 memcpy(buf, s->buffer.str, s->buffer.len);
206
207 return s->buffer.len;
208}
209
210static int webvtt_encode_close(AVCodecContext *avctx)
211{
212 WebVTTContext *s = avctx->priv_data;
213 ff_ass_split_free(s->ass_ctx);
214 av_bprint_finalize(&s->buffer, NULL);
215 return 0;
216}
217
218static av_cold int webvtt_encode_init(AVCodecContext *avctx)
219{
220 WebVTTContext *s = avctx->priv_data;
221 s->avctx = avctx;
222 s->ass_ctx = ff_ass_split(avctx->subtitle_header);
223 av_bprint_init(&s->buffer, 0, AV_BPRINT_SIZE_UNLIMITED);
224 return s->ass_ctx ? 0 : AVERROR_INVALIDDATA;
225}
226
227AVCodec ff_webvtt_encoder = {
228 .name = "webvtt",
229 .long_name = NULL_IF_CONFIG_SMALL("WebVTT subtitle"),
230 .type = AVMEDIA_TYPE_SUBTITLE,
231 .id = AV_CODEC_ID_WEBVTT,
232 .priv_data_size = sizeof(WebVTTContext),
233 .init = webvtt_encode_init,
234 .encode_sub = webvtt_encode_frame,
235 .close = webvtt_encode_close,
236};
237
generated by cgit at 2024-05-17 03:08:57 (GMT)