FFmpeg: libavformat/tedcaptionsdec.c Source File

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libavformat

tedcaptionsdec.c

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1 /*

2 * TED Talks captions format decoder

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 */

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"

29 typedef struct {

30 AVClass *class;

31 int64_t start_time;

32 FFDemuxSubtitlesQueue subs;

33 } TEDCaptionsDemuxer;

35 static const AVOption tedcaptions_options[] = {

36 { "start_time", "set the start time (offset) of the subtitles, in ms",

37 offsetof(TEDCaptionsDemuxer, start_time), FF_OPT_TYPE_INT64,

38 { .i64 = 15000 }, INT64_MIN, INT64_MAX,

39 AV_OPT_FLAG_SUBTITLE_PARAM | AV_OPT_FLAG_DECODING_PARAM },

40 { NULL },

41 };

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 };

50 #define BETWEEN(a, amin, amax) ((unsigned)((a) - (amin)) <= (amax) - (amin))

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)

56 static void av_bprint_utf8(AVBPrint *bp, unsigned c)

57 {

58 int bytes, i;

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 }

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 }

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 }

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 }

93 static int parse_string(AVIOContext *pb, int *cur_byte, AVBPrint *bp, int full)

94 {

95 int ret;

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 val = val * 10 + (*cur_byte - '0');

185 next_byte(pb, cur_byte);

186 }

187 *result = val;

188 return 0;

189 }

190

191 static int parse_file(AVIOContext *pb, FFDemuxSubtitlesQueue *subs)

192 {

193 int ret, cur_byte, start_of_par;

194 AVBPrint label, content;

195 int64_t pos, start, duration;

196 AVPacket *pkt;

197

198 next_byte(pb, &cur_byte);

199 ret = expect_byte(pb, &cur_byte, '{');

200 if (ret < 0)

201 return AVERROR_INVALIDDATA;

202 ret = parse_label(pb, &cur_byte, &label);

203 if (ret < 0 || strcmp(label.str, "captions"))

204 return AVERROR_INVALIDDATA;

205 ret = expect_byte(pb, &cur_byte, '[');

206 if (ret < 0)

207 return AVERROR_INVALIDDATA;

208 while (1) {

209 content.size = 0;

210 start = duration = AV_NOPTS_VALUE;

211 ret = expect_byte(pb, &cur_byte, '{');

212 if (ret < 0)

213 return ret;

214 pos = avio_tell(pb) - 1;

215 while (1) {

216 ret = parse_label(pb, &cur_byte, &label);

217 if (ret < 0)

218 return ret;

219 if (!strcmp(label.str, "startOfParagraph")) {

220 ret = parse_boolean(pb, &cur_byte, &start_of_par);

221 if (ret < 0)

222 return ret;

223 } else if (!strcmp(label.str, "content")) {

224 ret = parse_string(pb, &cur_byte, &content, 1);

225 if (ret < 0)

226 return ret;

227 } else if (!strcmp(label.str, "startTime")) {

228 ret = parse_int(pb, &cur_byte, &start);

229 if (ret < 0)

230 return ret;

231 } else if (!strcmp(label.str, "duration")) {

232 ret = parse_int(pb, &cur_byte, &duration);

233 if (ret < 0)

234 return ret;

235 } else {

236 return AVERROR_INVALIDDATA;

237 }

238 skip_spaces(pb, &cur_byte);

239 if (cur_byte != ',')

240 break;

241 next_byte(pb, &cur_byte);

242 }

243 ret = expect_byte(pb, &cur_byte, '}');

244 if (ret < 0)

245 return ret;

246

247 if (!content.size || start == AV_NOPTS_VALUE ||

248 duration == AV_NOPTS_VALUE)

249 return AVERROR_INVALIDDATA;

250 pkt = ff_subtitles_queue_insert(subs, content.str, content.len, 0);

251 if (!pkt)

252 return AVERROR(ENOMEM);

253 pkt->pos = pos;

254 pkt->pts = start;

255 pkt->duration = duration;

256 av_bprint_finalize(&content, NULL);

257

258 skip_spaces(pb, &cur_byte);

259 if (cur_byte != ',')

260 break;

261 next_byte(pb, &cur_byte);

262 }

263 ret = expect_byte(pb, &cur_byte, ']');

264 if (ret < 0)

265 return ret;

266 ret = expect_byte(pb, &cur_byte, '}');

267 if (ret < 0)

268 return ret;

269 skip_spaces(pb, &cur_byte);

270 if (cur_byte != AVERROR_EOF)

271 return ERR_CODE(cur_byte);

272 return 0;

273 }

274

275 static av_cold int tedcaptions_read_header(AVFormatContext *avf)

276 {

277 TEDCaptionsDemuxer *tc = avf->priv_data;

278 AVStream *st;

279 int ret, i;

280 AVPacket *last;

281

282 ret = parse_file(avf->pb, &tc->subs);

283 if (ret < 0) {

284 if (ret == AVERROR_INVALIDDATA)

285 av_log(avf, AV_LOG_ERROR, "Syntax error near offset %"PRId64".\n",

286 avio_tell(avf->pb));

287 ff_subtitles_queue_clean(&tc->subs);

288 return ret;

289 }

290 ff_subtitles_queue_finalize(&tc->subs);

291 for (i = 0; i < tc->subs.nb_subs; i++)

292 tc->subs.subs[i].pts += tc->start_time;

293

294 last = &tc->subs.subs[tc->subs.nb_subs - 1];

295 st = avformat_new_stream(avf, NULL);

296 if (!st)

297 return AVERROR(ENOMEM);

298 st->codec->codec_type = AVMEDIA_TYPE_SUBTITLE;

299 st->codec->codec_id = AV_CODEC_ID_TEXT;

300 avpriv_set_pts_info(st, 64, 1, 1000);

301 st->probe_packets = 0;

302 st->start_time = 0;

303 st->duration = last->pts + last->duration;

304 st->cur_dts = 0;

305

306 return 0;

307 }

308

309 static int tedcaptions_read_packet(AVFormatContext *avf, AVPacket *packet)

310 {

311 TEDCaptionsDemuxer *tc = avf->priv_data;

312

313 return ff_subtitles_queue_read_packet(&tc->subs, packet);

314 }

315

316 static int tedcaptions_read_close(AVFormatContext *avf)

317 {

318 TEDCaptionsDemuxer *tc = avf->priv_data;

319

320 ff_subtitles_queue_clean(&tc->subs);

321 return 0;

322 }

323

324 static av_cold int tedcaptions_read_probe(AVProbeData *p)

325 {

326 static const char *const tags[] = {

327 "\"captions\"", "\"duration\"", "\"content\"",

328 "\"startOfParagraph\"", "\"startTime\"",

329 };

330 unsigned i, count = 0;

331 const char *t;

332

333 if (p->buf[strspn(p->buf, " \t\r\n")] != '{')

334 return 0;

335 for (i = 0; i < FF_ARRAY_ELEMS(tags); i++) {

336 if (!(t = strstr(p->buf, tags[i])))

337 continue;

338 t += strlen(tags[i]);

339 t += strspn(t, " \t\r\n");

340 if (*t == ':')

341 count++;

342 }

343 return count == FF_ARRAY_ELEMS(tags) ? AVPROBE_SCORE_MAX :

344 count ? AVPROBE_SCORE_EXTENSION : 0;

345 }

346

347 static int tedcaptions_read_seek(AVFormatContext *avf, int stream_index,

348 int64_t min_ts, int64_t ts, int64_t max_ts,

349 int flags)

350 {

351 TEDCaptionsDemuxer *tc = avf->priv_data;

352 return ff_subtitles_queue_seek(&tc->subs, avf, stream_index,

353 min_ts, ts, max_ts, flags);

354 }

355

356 AVInputFormat ff_tedcaptions_demuxer = {

357 .name = "tedcaptions",

358 .long_name = NULL_IF_CONFIG_SMALL("TED Talks captions"),

359 .priv_data_size = sizeof(TEDCaptionsDemuxer),

360 .priv_class = &tedcaptions_demuxer_class,

361 .read_header = tedcaptions_read_header,

362 .read_packet = tedcaptions_read_packet,

363 .read_close = tedcaptions_read_close,

364 .read_probe = tedcaptions_read_probe,

365 .read_seek2 = tedcaptions_read_seek,

366 };

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