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1 /*
2  * SubRip subtitle demuxer
3  * Copyright (c) 2010  Aurelien Jacobs <aurel@gnuage.org>
4  * Copyright (c) 2015  Clément Bœsch <u pkh me>
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 "avformat.h"
24 #include "internal.h"
25 #include "subtitles.h"
26 #include "libavutil/bprint.h"
27 #include "libavutil/intreadwrite.h"
28 
29 typedef struct {
30     FFDemuxSubtitlesQueue q;
31 } SRTContext;
32 
srt_probe(const AVProbeData * p)33 static int srt_probe(const AVProbeData *p)
34 {
35     int v;
36     char buf[64], *pbuf;
37     FFTextReader tr;
38 
39     ff_text_init_buf(&tr, p->buf, p->buf_size);
40 
41     while (ff_text_peek_r8(&tr) == '\r' || ff_text_peek_r8(&tr) == '\n')
42         ff_text_r8(&tr);
43 
44     /* Check if the first non-empty line is a number. We do not check what the
45      * number is because in practice it can be anything.
46      * Also, that number can be followed by random garbage, so we can not
47      * unfortunately check that we only have a number. */
48     if (ff_subtitles_read_line(&tr, buf, sizeof(buf)) < 0 ||
49         strtol(buf, &pbuf, 10) < 0 || pbuf == buf)
50         return 0;
51 
52     /* Check if the next line matches a SRT timestamp */
53     if (ff_subtitles_read_line(&tr, buf, sizeof(buf)) < 0)
54         return 0;
55     pbuf = buf;
56     if (buf[0] == '-')
57         pbuf++;
58     if (pbuf[0] >= '0' && pbuf[0] <= '9' && strstr(buf, " --> ")
59         && sscanf(buf, "%*d:%*d:%*d%*1[,.]%*d --> %*d:%*d:%*d%*1[,.]%d", &v) == 1)
60         return AVPROBE_SCORE_MAX;
61 
62     return 0;
63 }
64 
65 struct event_info {
66     int32_t x1, x2, y1, y2;
67     int duration;
68     int64_t pts;
69     int64_t pos;
70 };
71 
get_event_info(const char * line,struct event_info * ei)72 static int get_event_info(const char *line, struct event_info *ei)
73 {
74     int hh1, mm1, ss1, ms1;
75     int hh2, mm2, ss2, ms2;
76 
77     ei->x1 = ei->x2 = ei->y1 = ei->y2 = ei->duration = -1;
78     ei->pts = AV_NOPTS_VALUE;
79     ei->pos = -1;
80     if (sscanf(line, "%d:%d:%d%*1[,.]%d --> %d:%d:%d%*1[,.]%d"
81                "%*[ ]X1:%"PRId32" X2:%"PRId32" Y1:%"PRId32" Y2:%"PRId32,
82                &hh1, &mm1, &ss1, &ms1,
83                &hh2, &mm2, &ss2, &ms2,
84                &ei->x1, &ei->x2, &ei->y1, &ei->y2) >= 8) {
85         const int64_t start = (hh1*3600LL + mm1*60LL + ss1) * 1000LL + ms1;
86         const int64_t end   = (hh2*3600LL + mm2*60LL + ss2) * 1000LL + ms2;
87         ei->duration = end - start;
88         ei->pts = start;
89         return 0;
90     }
91     return -1;
92 }
93 
add_event(FFDemuxSubtitlesQueue * q,AVBPrint * buf,char * line_cache,const struct event_info * ei,int append_cache)94 static int add_event(FFDemuxSubtitlesQueue *q, AVBPrint *buf, char *line_cache,
95                      const struct event_info *ei, int append_cache)
96 {
97     if (append_cache && line_cache[0])
98         av_bprintf(buf, "%s\n", line_cache);
99     line_cache[0] = 0;
100 
101     while (buf->len > 0 && buf->str[buf->len - 1] == '\n')
102         buf->str[--buf->len] = 0;
103 
104     if (buf->len) {
105         AVPacket *sub = ff_subtitles_queue_insert(q, buf->str, buf->len, 0);
106         if (!sub)
107             return AVERROR(ENOMEM);
108         av_bprint_clear(buf);
109         sub->pos = ei->pos;
110         sub->pts = ei->pts;
111         sub->duration = ei->duration;
112         if (ei->x1 != -1) {
113             uint8_t *p = av_packet_new_side_data(sub, AV_PKT_DATA_SUBTITLE_POSITION, 16);
114             if (p) {
115                 AV_WL32(p,      ei->x1);
116                 AV_WL32(p +  4, ei->y1);
117                 AV_WL32(p +  8, ei->x2);
118                 AV_WL32(p + 12, ei->y2);
119             }
120         }
121     }
122 
123     return 0;
124 }
125 
srt_read_header(AVFormatContext * s)126 static int srt_read_header(AVFormatContext *s)
127 {
128     SRTContext *srt = s->priv_data;
129     AVBPrint buf;
130     AVStream *st = avformat_new_stream(s, NULL);
131     int res = 0;
132     char line[4096], line_cache[4096];
133     int has_event_info = 0;
134     struct event_info ei;
135     FFTextReader tr;
136     ff_text_init_avio(s, &tr, s->pb);
137 
138     if (!st)
139         return AVERROR(ENOMEM);
140     avpriv_set_pts_info(st, 64, 1, 1000);
141     st->codecpar->codec_type = AVMEDIA_TYPE_SUBTITLE;
142     st->codecpar->codec_id   = AV_CODEC_ID_SUBRIP;
143 
144     av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
145 
146     line_cache[0] = 0;
147 
148     while (!ff_text_eof(&tr)) {
149         struct event_info tmp_ei;
150         const int64_t pos = ff_text_pos(&tr);
151         ptrdiff_t len = ff_subtitles_read_line(&tr, line, sizeof(line));
152 
153         if (len < 0)
154             break;
155 
156         if (!len || !line[0])
157             continue;
158 
159         if (get_event_info(line, &tmp_ei) < 0) {
160             char *pline;
161 
162             if (!has_event_info)
163                 continue;
164 
165             if (line_cache[0]) {
166                 /* We got some cache and a new line so we assume the cached
167                  * line was actually part of the payload */
168                 av_bprintf(&buf, "%s\n", line_cache);
169                 line_cache[0] = 0;
170             }
171 
172             /* If the line doesn't start with a number, we assume it's part of
173              * the payload, otherwise is likely an event number preceding the
174              * timing information... but we can't be sure of this yet, so we
175              * cache it */
176             if (strtol(line, &pline, 10) < 0 || line == pline)
177                 av_bprintf(&buf, "%s\n", line);
178             else
179                 strcpy(line_cache, line);
180         } else {
181             if (has_event_info) {
182                 /* We have the information of previous event, append it to the
183                  * queue. We insert the cached line if and only if the payload
184                  * is empty and the cached line is not a standalone number. */
185                 char *pline = NULL;
186                 const int standalone_number = strtol(line_cache, &pline, 10) >= 0 && pline && !*pline;
187                 res = add_event(&srt->q, &buf, line_cache, &ei, !buf.len && !standalone_number);
188                 if (res < 0)
189                     goto end;
190             } else {
191                 has_event_info = 1;
192             }
193             tmp_ei.pos = pos;
194             ei = tmp_ei;
195         }
196     }
197 
198     /* Append the last event. Here we force the cache to be flushed, because a
199      * trailing number is more likely to be geniune (for example a copyright
200      * date) and not the event index of an inexistant event */
201     if (has_event_info) {
202         res = add_event(&srt->q, &buf, line_cache, &ei, 1);
203         if (res < 0)
204             goto end;
205     }
206 
207     ff_subtitles_queue_finalize(s, &srt->q);
208 
209 end:
210     av_bprint_finalize(&buf, NULL);
211     return res;
212 }
213 
214 const AVInputFormat ff_srt_demuxer = {
215     .name        = "srt",
216     .long_name   = NULL_IF_CONFIG_SMALL("SubRip subtitle"),
217     .priv_data_size = sizeof(SRTContext),
218     .flags_internal = FF_FMT_INIT_CLEANUP,
219     .read_probe  = srt_probe,
220     .read_header = srt_read_header,
221     .read_packet = ff_subtitles_read_packet,
222     .read_seek2  = ff_subtitles_read_seek,
223     .read_close  = ff_subtitles_read_close,
224 };
225