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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 | |
31 | typedef 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 | |
44 | static 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 | ||
52 | static 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 | ||
60 | static 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 | ||
67 | static 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 | ||
76 | static void webvtt_close_tag(WebVTTContext *s, char tag) | |
77 | { | |
78 | webvtt_print(s, "</%c>", tag); | |
79 | } | |
80 | ||
81 | static 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 | ||
93 | static 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 | ||
112 | static 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 | ||
118 | static void webvtt_new_line_cb(void *priv, int forced) | |
119 | { | |
120 | webvtt_print(priv, "\n"); | |
121 | } | |
122 | ||
123 | static 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 | ||
133 | static 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 | ||
139 | static void webvtt_end_cb(void *priv) | |
140 | { | |
141 | webvtt_stack_push_pop(priv, 0, 1); | |
142 | } | |
143 | ||
144 | static 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 | ||
157 | static 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, num; | |
163 | ||
164 | av_bprint_clear(&s->buffer); | |
165 | ||
166 | for (i=0; i<sub->num_rects; i++) { | |
167 | if (sub->rects[i]->type != SUBTITLE_ASS) { | |
168 | av_log(avctx, AV_LOG_ERROR, "Only SUBTITLE_ASS type supported.\n"); | |
169 | return AVERROR(ENOSYS); | |
170 | } | |
171 | ||
172 | dialog = ff_ass_split_dialog(s->ass_ctx, sub->rects[i]->ass, 0, &num); | |
173 | for (; dialog && num--; dialog++) { | |
174 | webvtt_style_apply(s, dialog->style); | |
175 | ff_ass_split_override_codes(&webvtt_callbacks, s, dialog->text); | |
176 | } | |
177 | } | |
178 | ||
179 | if (!av_bprint_is_complete(&s->buffer)) | |
180 | return AVERROR(ENOMEM); | |
181 | if (!s->buffer.len) | |
182 | return 0; | |
183 | ||
184 | if (s->buffer.len > bufsize) { | |
185 | av_log(avctx, AV_LOG_ERROR, "Buffer too small for ASS event.\n"); | |
186 | return -1; | |
187 | } | |
188 | memcpy(buf, s->buffer.str, s->buffer.len); | |
189 | ||
190 | return s->buffer.len; | |
191 | } | |
192 | ||
193 | static int webvtt_encode_close(AVCodecContext *avctx) | |
194 | { | |
195 | WebVTTContext *s = avctx->priv_data; | |
196 | ff_ass_split_free(s->ass_ctx); | |
197 | av_bprint_finalize(&s->buffer, NULL); | |
198 | return 0; | |
199 | } | |
200 | ||
201 | static av_cold int webvtt_encode_init(AVCodecContext *avctx) | |
202 | { | |
203 | WebVTTContext *s = avctx->priv_data; | |
204 | s->avctx = avctx; | |
205 | s->ass_ctx = ff_ass_split(avctx->subtitle_header); | |
206 | av_bprint_init(&s->buffer, 0, AV_BPRINT_SIZE_UNLIMITED); | |
207 | return s->ass_ctx ? 0 : AVERROR_INVALIDDATA; | |
208 | } | |
209 | ||
210 | AVCodec ff_webvtt_encoder = { | |
211 | .name = "webvtt", | |
212 | .long_name = NULL_IF_CONFIG_SMALL("WebVTT subtitle"), | |
213 | .type = AVMEDIA_TYPE_SUBTITLE, | |
214 | .id = AV_CODEC_ID_WEBVTT, | |
215 | .priv_data_size = sizeof(WebVTTContext), | |
216 | .init = webvtt_encode_init, | |
217 | .encode_sub = webvtt_encode_frame, | |
218 | .close = webvtt_encode_close, | |
219 | }; |