libavformat/webvttdec.c
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1 /*
2  * Copyright (c) 2012 Clément Bœsch
3  *
4  * This file is part of FFmpeg.
5  *
6  * FFmpeg is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * FFmpeg is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with FFmpeg; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 /**
22  * @file
23  * WebVTT subtitle demuxer
24  * @see http://dev.w3.org/html5/webvtt/
25  */
26 
27 #include "avformat.h"
28 #include "internal.h"
29 #include "subtitles.h"
30 #include "libavutil/bprint.h"
31 #include "libavutil/intreadwrite.h"
32 
33 typedef struct {
36 
37 static int webvtt_probe(AVProbeData *p)
38 {
39  const uint8_t *ptr = p->buf;
40 
41  if (AV_RB24(ptr) == 0xEFBBBF)
42  ptr += 3; /* skip UTF-8 BOM */
43  if (!strncmp(ptr, "WEBVTT", 6) &&
44  (!ptr[6] || strchr("\n\r\t ", ptr[6])))
45  return AVPROBE_SCORE_MAX;
46  return 0;
47 }
48 
49 static int64_t read_ts(const char *s)
50 {
51  int hh, mm, ss, ms;
52  if (sscanf(s, "%u:%u:%u.%u", &hh, &mm, &ss, &ms) == 4) return (hh*3600LL + mm*60LL + ss) * 1000LL + ms;
53  if (sscanf(s, "%u:%u.%u", &mm, &ss, &ms) == 3) return ( mm*60LL + ss) * 1000LL + ms;
54  return AV_NOPTS_VALUE;
55 }
56 
58 {
59  WebVTTContext *webvtt = s->priv_data;
60  AVBPrint header, cue;
61  int res = 0;
63 
64  if (!st)
65  return AVERROR(ENOMEM);
66  avpriv_set_pts_info(st, 64, 1, 1000);
69 
72 
73  for (;;) {
74  int i;
75  int64_t pos;
76  AVPacket *sub;
77  const char *p, *identifier;
78  //const char *settings = NULL;
79  int64_t ts_start, ts_end;
80 
81  ff_subtitles_read_chunk(s->pb, &cue);
82 
83  if (!cue.len)
84  break;
85 
86  p = identifier = cue.str;
87  pos = avio_tell(s->pb);
88 
89  /* ignore header chunk */
90  if (!strncmp(p, "\xEF\xBB\xBFWEBVTT", 9) ||
91  !strncmp(p, "WEBVTT", 6))
92  continue;
93 
94  /* optional cue identifier (can be a number like in SRT or some kind of
95  * chaptering id), silently skip it */
96  for (i = 0; p[i] && p[i] != '\n'; i++) {
97  if (!strncmp(p + i, "-->", 3)) {
98  identifier = NULL;
99  break;
100  }
101  }
102  if (identifier)
103  p += strcspn(p, "\n");
104 
105  /* cue timestamps */
106  if ((ts_start = read_ts(p)) == AV_NOPTS_VALUE)
107  break;
108  if (!(p = strstr(p, "-->")))
109  break;
110  p += 3;
111  do p++; while (*p == ' ' || *p == '\t');
112  if ((ts_end = read_ts(p)) == AV_NOPTS_VALUE)
113  break;
114 
115  /* optional cue settings, TODO: store in side_data */
116  p += strcspn(p, "\n\t ");
117  while (*p == '\t' || *p == ' ')
118  p++;
119  if (*p != '\n') {
120  //settings = p;
121  p += strcspn(p, "\n");
122  }
123  if (*p == '\n')
124  p++;
125 
126  /* create packet */
127  sub = ff_subtitles_queue_insert(&webvtt->q, p, strlen(p), 0);
128  if (!sub) {
129  res = AVERROR(ENOMEM);
130  goto end;
131  }
132  sub->pos = pos;
133  sub->pts = ts_start;
134  sub->duration = ts_end - ts_start;
135  }
136 
137  ff_subtitles_queue_finalize(&webvtt->q);
138 
139 end:
140  av_bprint_finalize(&cue, NULL);
141  av_bprint_finalize(&header, NULL);
142  return res;
143 }
144 
146 {
147  WebVTTContext *webvtt = s->priv_data;
148  return ff_subtitles_queue_read_packet(&webvtt->q, pkt);
149 }
150 
151 static int webvtt_read_seek(AVFormatContext *s, int stream_index,
152  int64_t min_ts, int64_t ts, int64_t max_ts, int flags)
153 {
154  WebVTTContext *webvtt = s->priv_data;
155  return ff_subtitles_queue_seek(&webvtt->q, s, stream_index,
156  min_ts, ts, max_ts, flags);
157 }
158 
160 {
161  WebVTTContext *webvtt = s->priv_data;
162  ff_subtitles_queue_clean(&webvtt->q);
163  return 0;
164 }
165 
167  .name = "webvtt",
168  .long_name = NULL_IF_CONFIG_SMALL("WebVTT subtitle"),
169  .priv_data_size = sizeof(WebVTTContext),
173  .read_seek2 = webvtt_read_seek,
175  .extensions = "vtt",
176 };
static int webvtt_read_close(AVFormatContext *s)
const char * s
Definition: avisynth_c.h:668
static int webvtt_read_header(AVFormatContext *s)
int64_t pos
byte position in stream, -1 if unknown
void avpriv_set_pts_info(AVStream *s, int pts_wrap_bits, unsigned int pts_num, unsigned int pts_den)
Set the time base and wrapping info for a given stream.
void ff_subtitles_read_chunk(AVIOContext *pb, AVBPrint *buf)
Read a subtitles chunk.
Definition: subtitles.c:192
#define AV_RB24
void ff_subtitles_queue_clean(FFDemuxSubtitlesQueue *q)
Remove and destroy all the subtitles packets.
Definition: subtitles.c:134
AVPacket * ff_subtitles_queue_insert(FFDemuxSubtitlesQueue *q, const uint8_t *event, int len, int merge)
Insert a new subtitle event.
Definition: subtitles.c:26
static int webvtt_read_seek(AVFormatContext *s, int stream_index, int64_t min_ts, int64_t ts, int64_t max_ts, int flags)
int av_bprint_finalize(AVBPrint *buf, char **ret_str)
Finalize a print buffer.
Definition: bprint.c:193
Format I/O context.
Definition: avformat.h:944
uint8_t
int ff_subtitles_queue_read_packet(FFDemuxSubtitlesQueue *q, AVPacket *pkt)
Generic read_packet() callback for subtitles demuxers using this queue system.
Definition: subtitles.c:82
static AVPacket pkt
Definition: demuxing.c:56
end end
AVStream * avformat_new_stream(AVFormatContext *s, const AVCodec *c)
Add a new stream to a media file.
static av_cold int read_close(AVFormatContext *ctx)
Definition: libcdio.c:145
static av_always_inline int64_t avio_tell(AVIOContext *s)
ftell() equivalent for AVIOContext.
Definition: avio.h:248
int duration
Duration of this packet in AVStream->time_base units, 0 if unknown.
#define AV_BPRINT_SIZE_UNLIMITED
Convenience macros for special values for av_bprint_init() size_max parameter.
Definition: bprint.h:89
AVInputFormat ff_webvtt_demuxer
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
void av_bprint_init(AVBPrint *buf, unsigned size_init, unsigned size_max)
Init a print buffer.
Definition: bprint.c:68
AVCodecContext * codec
Codec context associated with this stream.
Definition: avformat.h:662
unsigned char * buf
Buffer must have AVPROBE_PADDING_SIZE of extra allocated bytes filled with zero.
Definition: avformat.h:336
Buffer to print data progressively.
Definition: bprint.h:75
static int read_probe(AVProbeData *pd)
void ff_subtitles_queue_finalize(FFDemuxSubtitlesQueue *q)
Set missing durations and sort subtitles by PTS, and then byte position.
Definition: subtitles.c:72
static int read_header(FFV1Context *f)
Definition: ffv1dec.c:517
Stream structure.
Definition: avformat.h:643
NULL
Definition: eval.c:55
int ff_subtitles_queue_seek(FFDemuxSubtitlesQueue *q, AVFormatContext *s, int stream_index, int64_t min_ts, int64_t ts, int64_t max_ts, int flags)
Update current_sub_idx to emulate a seek.
Definition: subtitles.c:95
enum AVMediaType codec_type
enum AVCodecID codec_id
AVIOContext * pb
I/O context.
Definition: avformat.h:977
static int read_packet(AVFormatContext *ctx, AVPacket *pkt)
Definition: libcdio.c:114
synthesis window for stochastic i
This structure contains the data a format has to probe a file.
Definition: avformat.h:334
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFilterBuffer structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later.That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another.Buffer references ownership and permissions
static int64_t read_ts(const char *s)
static int flags
Definition: cpu.c:23
#define AVPROBE_SCORE_MAX
maximum score, half of that is used for file-extension-based detection
Definition: avformat.h:340
Main libavformat public API header.
FFDemuxSubtitlesQueue q
void * priv_data
Format private data.
Definition: avformat.h:964
const char * name
A comma separated list of short names for the format.
Definition: avformat.h:461
static int webvtt_read_packet(AVFormatContext *s, AVPacket *pkt)
This structure stores compressed data.
int64_t pts
Presentation timestamp in AVStream->time_base units; the time at which the decompressed packet will b...
static int webvtt_probe(AVProbeData *p)
#define AV_NOPTS_VALUE
Undefined timestamp value.
Definition: avutil.h:190