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
29typedef struct {
30    AVClass *class;
31    int64_t start_time;
32    FFDemuxSubtitlesQueue subs;
33} TEDCaptionsDemuxer;
34
35static 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};
42
43static 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
56static 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
70static 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
77static 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
84static 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
93static 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
136fail:
137    av_bprint_finalize(bp, NULL);
138    return ret;
139}
140
141static 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
154static 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
176static 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
191static 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
275static 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
309static 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
316static 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
324static 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
347static 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
356AVInputFormat 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};
367