libavformat/tedcaptionsdec.c

   1 /*
   2  * TED Talks captions format decoder
   3  * Copyright (c) 2012 Nicolas George
   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 #include "libavutil/bprint.h"
  23 #include "libavutil/log.h"
  24 #include "libavutil/opt.h"
  25 #include "avformat.h"
  26 #include "internal.h"
  27 #include "subtitles.h"
  28
  29 typedef struct {
  30     AVClass *class;
  31     int64_t start_time;
  32     FFDemuxSubtitlesQueue subs;
  33 } TEDCaptionsDemuxer;
  34
  35 static const AVOption tedcaptions_options[] = {
  36     { "start_time", "set the start time (offset) of the subtitles, in ms",
  37       offsetof(TEDCaptionsDemuxer, start_time), AV_OPT_TYPE_INT64,
  38       { .i64 = 15000 }, INT64_MIN, INT64_MAX,
  39       AV_OPT_FLAG_SUBTITLE_PARAM | AV_OPT_FLAG_DECODING_PARAM },
  40     { NULL },
  41 };
  42
  43 static const AVClass tedcaptions_demuxer_class = {
  44     .class_name = "tedcaptions_demuxer",
  45     .item_name  = av_default_item_name,
  46     .option     = tedcaptions_options,
  47     .version    = LIBAVUTIL_VERSION_INT,
  48 };
  49
  50 #define BETWEEN(a, amin, amax) ((unsigned)((a) - (amin)) <= (amax) - (amin))
  51
  52 #define HEX_DIGIT_TEST(c) (BETWEEN(c, '0', '9') || BETWEEN((c) | 32, 'a', 'z'))
  53 #define HEX_DIGIT_VAL(c) ((c) <= '9' ? (c) - '0' : ((c) | 32) - 'a' + 10)
  54 #define ERR_CODE(c) ((c) < 0 ? (c) : AVERROR_INVALIDDATA)
  55
  56 static void av_bprint_utf8(AVBPrint *bp, unsigned c)
  57 {
  58     int bytes, i;
  59
  60     if (c <= 0x7F) {
  61         av_bprint_chars(bp, c, 1);
  62         return;
  63     }
  64     bytes = (av_log2(c) - 2) / 5;
  65     av_bprint_chars(bp, (c >> (bytes * 6)) | ((0xFF80 >> bytes) & 0xFF), 1);
  66     for (i = bytes - 1; i >= 0; i--)
  67         av_bprint_chars(bp, ((c >> (i * 6)) & 0x3F) | 0x80, 1);
  68 }
  69
  70 static void next_byte(AVIOContext *pb, int *cur_byte)
  71 {
  72     uint8_t b;
  73     int ret = avio_read(pb, &b, 1);
  74     *cur_byte = ret > 0 ? b : ret == 0 ? AVERROR_EOF : ret;
  75 }
  76
  77 static void skip_spaces(AVIOContext *pb, int *cur_byte)
  78 {
  79     while (*cur_byte == ' '  || *cur_byte == '\t' ||
  80            *cur_byte == '\n' || *cur_byte == '\r')
  81         next_byte(pb, cur_byte);
  82 }
  83
  84 static int expect_byte(AVIOContext *pb, int *cur_byte, uint8_t c)
  85 {
  86     skip_spaces(pb, cur_byte);
  87     if (*cur_byte != c)
  88         return ERR_CODE(*cur_byte);
  89     next_byte(pb, cur_byte);
  90     return 0;
  91 }
  92
  93 static int parse_string(AVIOContext *pb, int *cur_byte, AVBPrint *bp, int full)
  94 {
  95     int ret;
  96
  97     av_bprint_init(bp, 0, full ? -1 : 1);
  98     ret = expect_byte(pb, cur_byte, '"');
  99     if (ret < 0)
 100         goto fail;
 101     while (*cur_byte > 0 && *cur_byte != '"') {
 102         if (*cur_byte == '\\') {
 103             next_byte(pb, cur_byte);
 104             if (*cur_byte < 0) {
 105                 ret = AVERROR_INVALIDDATA;
 106                 goto fail;
 107             }
 108             if ((*cur_byte | 32) == 'u') {
 109                 unsigned chr = 0, i;
 110                 for (i = 0; i < 4; i++) {
 111                     next_byte(pb, cur_byte);
 112                     if (!HEX_DIGIT_TEST(*cur_byte)) {
 113                         ret = ERR_CODE(*cur_byte);
 114                         goto fail;
 115                     }
 116                     chr = chr * 16 + HEX_DIGIT_VAL(*cur_byte);
 117                 }
 118                 av_bprint_utf8(bp, chr);
 119             } else {
 120                 av_bprint_chars(bp, *cur_byte, 1);
 121             }
 122         } else {
 123             av_bprint_chars(bp, *cur_byte, 1);
 124         }
 125         next_byte(pb, cur_byte);
 126     }
 127     ret = expect_byte(pb, cur_byte, '"');
 128     if (ret < 0)
 129         goto fail;
 130     if (full && !av_bprint_is_complete(bp)) {
 131         ret = AVERROR(ENOMEM);
 132         goto fail;
 133     }
 134     return 0;
 135
 136 fail:
 137     av_bprint_finalize(bp, NULL);
 138     return ret;
 139 }
 140
 141 static int parse_label(AVIOContext *pb, int *cur_byte, AVBPrint *bp)
 142 {
 143     int ret;
 144
 145     ret = parse_string(pb, cur_byte, bp, 0);
 146     if (ret < 0)
 147         return ret;
 148     ret = expect_byte(pb, cur_byte, ':');
 149     if (ret < 0)
 150         return ret;
 151     return 0;
 152 }
 153
 154 static int parse_boolean(AVIOContext *pb, int *cur_byte, int *result)
 155 {
 156     static const char * const text[] = { "false", "true" };
 157     const char *p;
 158     int i;
 159
 160     skip_spaces(pb, cur_byte);
 161     for (i = 0; i < 2; i++) {
 162         p = text[i];
 163         if (*cur_byte != *p)
 164             continue;
 165         for (; *p; p++, next_byte(pb, cur_byte))
 166             if (*cur_byte != *p)
 167                 return AVERROR_INVALIDDATA;
 168         if (BETWEEN(*cur_byte | 32, 'a', 'z'))
 169             return AVERROR_INVALIDDATA;
 170         *result = i;
 171         return 0;
 172     }
 173     return AVERROR_INVALIDDATA;
 174 }
 175
 176 static int parse_int(AVIOContext *pb, int *cur_byte, int64_t *result)
 177 {
 178     int64_t val = 0;
 179
 180     skip_spaces(pb, cur_byte);
 181     if ((unsigned)*cur_byte - '0' > 9)
 182         return AVERROR_INVALIDDATA;
 183     while (BETWEEN(*cur_byte, '0', '9')) {
 184         if (val > INT_MAX/10 - (*cur_byte - '0'))
 185             return AVERROR_INVALIDDATA;
 186         val = val * 10 + (*cur_byte - '0');
 187         next_byte(pb, cur_byte);
 188     }
 189     *result = val;
 190     return 0;
 191 }
 192
 193 static int parse_file(AVIOContext *pb, FFDemuxSubtitlesQueue *subs)
 194 {
 195     int ret, cur_byte, start_of_par;
 196     AVBPrint label, content;
 197     int64_t pos, start, duration;
 198     AVPacket *pkt;
 199
 200     next_byte(pb, &cur_byte);
 201     ret = expect_byte(pb, &cur_byte, '{');
 202     if (ret < 0)
 203         return AVERROR_INVALIDDATA;
 204     ret = parse_label(pb, &cur_byte, &label);
 205     if (ret < 0 || strcmp(label.str, "captions"))
 206         return AVERROR_INVALIDDATA;
 207     ret = expect_byte(pb, &cur_byte, '[');
 208     if (ret < 0)
 209         return AVERROR_INVALIDDATA;
 210     while (1) {
 211         content.size = 0;
 212         start = duration = AV_NOPTS_VALUE;
 213         ret = expect_byte(pb, &cur_byte, '{');
 214         if (ret < 0)
 215             return ret;
 216         pos = avio_tell(pb) - 1;
 217         while (1) {
 218             ret = parse_label(pb, &cur_byte, &label);
 219             if (ret < 0)
 220                 return ret;
 221             if (!strcmp(label.str, "startOfParagraph")) {
 222                 ret = parse_boolean(pb, &cur_byte, &start_of_par);
 223                 if (ret < 0)
 224                     return ret;
 225             } else if (!strcmp(label.str, "content")) {
 226                 ret = parse_string(pb, &cur_byte, &content, 1);
 227                 if (ret < 0)
 228                     return ret;
 229             } else if (!strcmp(label.str, "startTime")) {
 230                 ret = parse_int(pb, &cur_byte, &start);
 231                 if (ret < 0)
 232                     return ret;
 233             } else if (!strcmp(label.str, "duration")) {
 234                 ret = parse_int(pb, &cur_byte, &duration);
 235                 if (ret < 0)
 236                     return ret;
 237             } else {
 238                 return AVERROR_INVALIDDATA;
 239             }
 240             skip_spaces(pb, &cur_byte);
 241             if (cur_byte != ',')
 242                 break;
 243             next_byte(pb, &cur_byte);
 244         }
 245         ret = expect_byte(pb, &cur_byte, '}');
 246         if (ret < 0)
 247             return ret;
 248
 249         if (!content.size || start == AV_NOPTS_VALUE ||
 250             duration == AV_NOPTS_VALUE)
 251             return AVERROR_INVALIDDATA;
 252         pkt = ff_subtitles_queue_insert(subs, content.str, content.len, 0);
 253         if (!pkt)
 254             return AVERROR(ENOMEM);
 255         pkt->pos      = pos;
 256         pkt->pts      = start;
 257         pkt->duration = duration;
 258         av_bprint_finalize(&content, NULL);
 259
 260         skip_spaces(pb, &cur_byte);
 261         if (cur_byte != ',')
 262             break;
 263         next_byte(pb, &cur_byte);
 264     }
 265     ret = expect_byte(pb, &cur_byte, ']');
 266     if (ret < 0)
 267         return ret;
 268     ret = expect_byte(pb, &cur_byte, '}');
 269     if (ret < 0)
 270         return ret;
 271     skip_spaces(pb, &cur_byte);
 272     if (cur_byte != AVERROR_EOF)
 273         return ERR_CODE(cur_byte);
 274     return 0;
 275 }
 276
 277 static av_cold int tedcaptions_read_header(AVFormatContext *avf)
 278 {
 279     TEDCaptionsDemuxer *tc = avf->priv_data;
 280     AVStream *st = avformat_new_stream(avf, NULL);
 281     int ret, i;
 282     AVPacket *last;
 283
 284     if (!st)
 285         return AVERROR(ENOMEM);
 286
 287     ret = parse_file(avf->pb, &tc->subs);
 288     if (ret < 0) {
 289         if (ret == AVERROR_INVALIDDATA)
 290             av_log(avf, AV_LOG_ERROR, "Syntax error near offset %"PRId64".\n",
 291                    avio_tell(avf->pb));
 292         ff_subtitles_queue_clean(&tc->subs);
 293         return ret;
 294     }
 295     ff_subtitles_queue_finalize(avf, &tc->subs);
 296     for (i = 0; i < tc->subs.nb_subs; i++)
 297         tc->subs.subs[i].pts += tc->start_time;
 298
 299     last = &tc->subs.subs[tc->subs.nb_subs - 1];
 300     st->codecpar->codec_type     = AVMEDIA_TYPE_SUBTITLE;
 301     st->codecpar->codec_id       = AV_CODEC_ID_TEXT;
 302     avpriv_set_pts_info(st, 64, 1, 1000);
 303     st->probe_packets = 0;
 304     st->start_time    = 0;
 305     st->duration      = last->pts + last->duration;
 306     st->cur_dts       = 0;
 307
 308     return 0;
 309 }
 310
 311 static int tedcaptions_read_packet(AVFormatContext *avf, AVPacket *packet)
 312 {
 313     TEDCaptionsDemuxer *tc = avf->priv_data;
 314
 315     return ff_subtitles_queue_read_packet(&tc->subs, packet);
 316 }
 317
 318 static int tedcaptions_read_close(AVFormatContext *avf)
 319 {
 320     TEDCaptionsDemuxer *tc = avf->priv_data;
 321
 322     ff_subtitles_queue_clean(&tc->subs);
 323     return 0;
 324 }
 325
 326 static av_cold int tedcaptions_read_probe(AVProbeData *p)
 327 {
 328     static const char *const tags[] = {
 329         "\"captions\"", "\"duration\"", "\"content\"",
 330         "\"startOfParagraph\"", "\"startTime\"",
 331     };
 332     unsigned i, count = 0;
 333     const char *t;
 334
 335     if (p->buf[strspn(p->buf, " \t\r\n")] != '{')
 336         return 0;
 337     for (i = 0; i < FF_ARRAY_ELEMS(tags); i++) {
 338         if (!(t = strstr(p->buf, tags[i])))
 339             continue;
 340         t += strlen(tags[i]);
 341         t += strspn(t, " \t\r\n");
 342         if (*t == ':')
 343             count++;
 344     }
 345     return count == FF_ARRAY_ELEMS(tags) ? AVPROBE_SCORE_MAX :
 346            count                         ? AVPROBE_SCORE_EXTENSION : 0;
 347 }
 348
 349 static int tedcaptions_read_seek(AVFormatContext *avf, int stream_index,
 350                                  int64_t min_ts, int64_t ts, int64_t max_ts,
 351                                  int flags)
 352 {
 353     TEDCaptionsDemuxer *tc = avf->priv_data;
 354     return ff_subtitles_queue_seek(&tc->subs, avf, stream_index,
 355                                    min_ts, ts, max_ts, flags);
 356 }
 357
 358 AVInputFormat ff_tedcaptions_demuxer = {
 359     .name           = "tedcaptions",
 360     .long_name      = NULL_IF_CONFIG_SMALL("TED Talks captions"),
 361     .priv_data_size = sizeof(TEDCaptionsDemuxer),
 362     .priv_class     = &tedcaptions_demuxer_class,
 363     .read_header    = tedcaptions_read_header,
 364     .read_packet    = tedcaptions_read_packet,
 365     .read_close     = tedcaptions_read_close,
 366     .read_probe     = tedcaptions_read_probe,
 367     .read_seek2     = tedcaptions_read_seek,
 368 };