| 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 | }; |