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, 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 193static 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 201static 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 210AVCodec 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}; 220