FFmpeg
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 #include "libavutil/opt.h"
33 
34 typedef struct {
35  const AVClass *class;
37  int kind;
39 
40 static int webvtt_probe(const AVProbeData *p)
41 {
42  const uint8_t *ptr = p->buf;
43 
44  if (AV_RB24(ptr) == 0xEFBBBF)
45  ptr += 3; /* skip UTF-8 BOM */
46  if (!strncmp(ptr, "WEBVTT", 6) &&
47  (!ptr[6] || strchr("\n\r\t ", ptr[6])))
48  return AVPROBE_SCORE_MAX;
49  return 0;
50 }
51 
52 static int64_t read_ts(const char *s)
53 {
54  int hh, mm, ss, ms;
55  if (sscanf(s, "%u:%u:%u.%u", &hh, &mm, &ss, &ms) == 4) return (hh*3600LL + mm*60LL + ss) * 1000LL + ms;
56  if (sscanf(s, "%u:%u.%u", &mm, &ss, &ms) == 3) return ( mm*60LL + ss) * 1000LL + ms;
57  return AV_NOPTS_VALUE;
58 }
59 
61 {
62  WebVTTContext *webvtt = s->priv_data;
63  AVBPrint cue;
64  int res = 0;
66 
67  if (!st)
68  return AVERROR(ENOMEM);
69  avpriv_set_pts_info(st, 64, 1, 1000);
72  st->disposition |= webvtt->kind;
73 
75 
76  for (;;) {
77  int i;
78  int64_t pos;
79  AVPacket *sub;
80  const char *p, *identifier, *settings;
81  size_t identifier_len, settings_len;
82  int64_t ts_start, ts_end;
83 
84  res = ff_subtitles_read_chunk(s->pb, &cue);
85  if (res < 0)
86  goto end;
87 
88  if (!cue.len)
89  break;
90 
91  p = identifier = cue.str;
92  pos = avio_tell(s->pb);
93 
94  /* ignore header chunk */
95  if (!strncmp(p, "\xEF\xBB\xBFWEBVTT", 9) ||
96  !strncmp(p, "WEBVTT", 6) ||
97  !strncmp(p, "NOTE", 4))
98  continue;
99 
100  /* optional cue identifier (can be a number like in SRT or some kind of
101  * chaptering id) */
102  for (i = 0; p[i] && p[i] != '\n' && p[i] != '\r'; i++) {
103  if (!strncmp(p + i, "-->", 3)) {
104  identifier = NULL;
105  break;
106  }
107  }
108  if (!identifier)
109  identifier_len = 0;
110  else {
111  identifier_len = strcspn(p, "\r\n");
112  p += identifier_len;
113  if (*p == '\r')
114  p++;
115  if (*p == '\n')
116  p++;
117  }
118 
119  /* cue timestamps */
120  if ((ts_start = read_ts(p)) == AV_NOPTS_VALUE)
121  break;
122  if (!(p = strstr(p, "-->")))
123  break;
124  p += 2;
125  do p++; while (*p == ' ' || *p == '\t');
126  if ((ts_end = read_ts(p)) == AV_NOPTS_VALUE)
127  break;
128 
129  /* optional cue settings */
130  p += strcspn(p, "\n\r\t ");
131  while (*p == '\t' || *p == ' ')
132  p++;
133  settings = p;
134  settings_len = strcspn(p, "\r\n");
135  p += settings_len;
136  if (*p == '\r')
137  p++;
138  if (*p == '\n')
139  p++;
140 
141  /* create packet */
142  sub = ff_subtitles_queue_insert(&webvtt->q, p, strlen(p), 0);
143  if (!sub) {
144  res = AVERROR(ENOMEM);
145  goto end;
146  }
147  sub->pos = pos;
148  sub->pts = ts_start;
149  sub->duration = ts_end - ts_start;
150 
151 #define SET_SIDE_DATA(name, type) do { \
152  if (name##_len) { \
153  uint8_t *buf = av_packet_new_side_data(sub, type, name##_len); \
154  if (!buf) { \
155  res = AVERROR(ENOMEM); \
156  goto end; \
157  } \
158  memcpy(buf, name, name##_len); \
159  } \
160 } while (0)
161 
164  }
165 
166  ff_subtitles_queue_finalize(s, &webvtt->q);
167 
168 end:
169  av_bprint_finalize(&cue, NULL);
170  return res;
171 }
172 
174 {
175  WebVTTContext *webvtt = s->priv_data;
176  return ff_subtitles_queue_read_packet(&webvtt->q, pkt);
177 }
178 
179 static int webvtt_read_seek(AVFormatContext *s, int stream_index,
180  int64_t min_ts, int64_t ts, int64_t max_ts, int flags)
181 {
182  WebVTTContext *webvtt = s->priv_data;
183  return ff_subtitles_queue_seek(&webvtt->q, s, stream_index,
184  min_ts, ts, max_ts, flags);
185 }
186 
188 {
189  WebVTTContext *webvtt = s->priv_data;
190  ff_subtitles_queue_clean(&webvtt->q);
191  return 0;
192 }
193 
194 #define OFFSET(x) offsetof(WebVTTContext, x)
195 #define KIND_FLAGS AV_OPT_FLAG_SUBTITLE_PARAM|AV_OPT_FLAG_DECODING_PARAM
196 
197 static const AVOption options[] = {
198  { "kind", "Set kind of WebVTT track", OFFSET(kind), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, KIND_FLAGS, .unit = "webvtt_kind" },
199  { "subtitles", "WebVTT subtitles kind", 0, AV_OPT_TYPE_CONST, { .i64 = 0 }, INT_MIN, INT_MAX, KIND_FLAGS, .unit = "webvtt_kind" },
200  { "captions", "WebVTT captions kind", 0, AV_OPT_TYPE_CONST, { .i64 = AV_DISPOSITION_CAPTIONS }, INT_MIN, INT_MAX, KIND_FLAGS, .unit = "webvtt_kind" },
201  { "descriptions", "WebVTT descriptions kind", 0, AV_OPT_TYPE_CONST, { .i64 = AV_DISPOSITION_DESCRIPTIONS }, INT_MIN, INT_MAX, KIND_FLAGS, .unit = "webvtt_kind" },
202  { "metadata", "WebVTT metadata kind", 0, AV_OPT_TYPE_CONST, { .i64 = AV_DISPOSITION_METADATA }, INT_MIN, INT_MAX, KIND_FLAGS, .unit = "webvtt_kind" },
203  { NULL }
204 };
205 
207  .class_name = "WebVTT demuxer",
208  .item_name = av_default_item_name,
209  .option = options,
210  .version = LIBAVUTIL_VERSION_INT,
211 };
212 
214  .name = "webvtt",
215  .long_name = NULL_IF_CONFIG_SMALL("WebVTT subtitle"),
216  .priv_data_size = sizeof(WebVTTContext),
217  .flags_internal = FF_FMT_INIT_CLEANUP,
221  .read_seek2 = webvtt_read_seek,
223  .extensions = "vtt",
224  .priv_class = &webvtt_demuxer_class,
225 };
AVMEDIA_TYPE_SUBTITLE
@ AVMEDIA_TYPE_SUBTITLE
Definition: avutil.h:204
AV_BPRINT_SIZE_UNLIMITED
#define AV_BPRINT_SIZE_UNLIMITED
FF_FMT_INIT_CLEANUP
#define FF_FMT_INIT_CLEANUP
For an AVInputFormat with this flag set read_close() needs to be called by the caller upon read_heade...
Definition: internal.h:46
AVERROR
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame 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. Frame references ownership and permissions
opt.h
AVCodecParameters::codec_type
enum AVMediaType codec_type
General type of the encoded data.
Definition: codec_par.h:51
av_bprint_init
void av_bprint_init(AVBPrint *buf, unsigned size_init, unsigned size_max)
Definition: bprint.c:69
avformat_new_stream
AVStream * avformat_new_stream(AVFormatContext *s, const struct AVCodec *c)
Add a new stream to a media file.
WebVTTContext
Definition: webvttenc.c:31
AVOption
AVOption.
Definition: opt.h:294
AVPacket::duration
int64_t duration
Duration of this packet in AVStream->time_base units, 0 if unknown.
Definition: packet.h:540
ff_subtitles_read_chunk
int ff_subtitles_read_chunk(AVIOContext *pb, AVBPrint *buf)
Same as ff_subtitles_read_text_chunk(), but read from an AVIOContext.
Definition: subtitles.c:437
AVPROBE_SCORE_MAX
#define AVPROBE_SCORE_MAX
maximum score
Definition: avformat.h:464
OFFSET
#define OFFSET(x)
Definition: webvttdec.c:194
avpriv_set_pts_info
void avpriv_set_pts_info(AVStream *st, int pts_wrap_bits, unsigned int pts_num, unsigned int pts_den)
Set the time base and wrapping info for a given stream.
Definition: avformat.c:843
read_close
static av_cold int read_close(AVFormatContext *ctx)
Definition: libcdio.c:143
avio_tell
static av_always_inline int64_t avio_tell(AVIOContext *s)
ftell() equivalent for AVIOContext.
Definition: avio.h:513
ss
#define ss(width, name, subs,...)
Definition: cbs_vp9.c:202
AV_PKT_DATA_WEBVTT_SETTINGS
@ AV_PKT_DATA_WEBVTT_SETTINGS
The optional settings (rendering instructions) that immediately follow the timestamp specifier of a W...
Definition: packet.h:203
ff_subtitles_queue_seek
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:261
pkt
AVPacket * pkt
Definition: movenc.c:59
AVInputFormat
Definition: avformat.h:549
read_packet
static int read_packet(void *opaque, uint8_t *buf, int buf_size)
Definition: avio_read_callback.c:41
intreadwrite.h
s
#define s(width, name)
Definition: cbs_vp9.c:198
ff_webvtt_demuxer
const AVInputFormat ff_webvtt_demuxer
Definition: webvttdec.c:213
AVInputFormat::name
const char * name
A comma separated list of short names for the format.
Definition: avformat.h:554
AVProbeData::buf
unsigned char * buf
Buffer must have AVPROBE_PADDING_SIZE of extra allocated bytes filled with zero.
Definition: avformat.h:454
ff_subtitles_queue_read_packet
int ff_subtitles_queue_read_packet(FFDemuxSubtitlesQueue *q, AVPacket *pkt)
Generic read_packet() callback for subtitles demuxers using this queue system.
Definition: subtitles.c:222
AV_CODEC_ID_WEBVTT
@ AV_CODEC_ID_WEBVTT
Definition: codec_id.h:570
AVFormatContext
Format I/O context.
Definition: avformat.h:1363
internal.h
AVStream::codecpar
AVCodecParameters * codecpar
Codec parameters associated with this stream.
Definition: avformat.h:864
LIBAVUTIL_VERSION_INT
#define LIBAVUTIL_VERSION_INT
Definition: version.h:85
read_header
static int read_header(FFV1Context *f)
Definition: ffv1dec.c:550
AVClass
Describe the class of an AVClass context structure.
Definition: log.h:66
NULL
#define NULL
Definition: coverity.c:32
av_default_item_name
const char * av_default_item_name(void *ptr)
Return the context name.
Definition: log.c:237
AVProbeData
This structure contains the data a format has to probe a file.
Definition: avformat.h:452
KIND_FLAGS
#define KIND_FLAGS
Definition: webvttdec.c:195
AV_DISPOSITION_METADATA
#define AV_DISPOSITION_METADATA
The subtitle stream contains time-aligned metadata that is not intended to be directly presented to t...
Definition: avformat.h:801
ff_subtitles_queue_insert
AVPacket * ff_subtitles_queue_insert(FFDemuxSubtitlesQueue *q, const uint8_t *event, size_t len, int merge)
Insert a new subtitle event.
Definition: subtitles.c:109
webvtt_demuxer_class
static const AVClass webvtt_demuxer_class
Definition: webvttdec.c:206
AV_DISPOSITION_CAPTIONS
#define AV_DISPOSITION_CAPTIONS
The subtitle stream contains captions, providing a transcription and possibly a translation of audio.
Definition: avformat.h:790
NULL_IF_CONFIG_SMALL
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification.
Definition: internal.h:106
av_bprint_finalize
int av_bprint_finalize(AVBPrint *buf, char **ret_str)
Finalize a print buffer.
Definition: bprint.c:240
AV_NOPTS_VALUE
#define AV_NOPTS_VALUE
Undefined timestamp value.
Definition: avutil.h:248
ff_subtitles_queue_finalize
void ff_subtitles_queue_finalize(void *log_ctx, FFDemuxSubtitlesQueue *q)
Set missing durations, sort subtitles by PTS (and then byte position), and drop duplicated events.
Definition: subtitles.c:204
FFDemuxSubtitlesQueue
Definition: subtitles.h:103
ff_subtitles_queue_clean
void ff_subtitles_queue_clean(FFDemuxSubtitlesQueue *q)
Remove and destroy all the subtitles packets.
Definition: subtitles.c:313
read_ts
static int64_t read_ts(const char *s)
Definition: webvttdec.c:52
bprint.h
i
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:255
AVPacket::pts
int64_t pts
Presentation timestamp in AVStream->time_base units; the time at which the decompressed packet will b...
Definition: packet.h:515
SET_SIDE_DATA
#define SET_SIDE_DATA(name, type)
WebVTTContext::q
FFDemuxSubtitlesQueue q
Definition: webvttdec.c:36
AVStream::disposition
int disposition
Stream disposition - a combination of AV_DISPOSITION_* flags.
Definition: avformat.h:910
AVStream
Stream structure.
Definition: avformat.h:841
AVClass::class_name
const char * class_name
The name of the class; usually it is the same name as the context structure type to which the AVClass...
Definition: log.h:71
pos
unsigned int pos
Definition: spdifenc.c:413
avformat.h
AV_DISPOSITION_DESCRIPTIONS
#define AV_DISPOSITION_DESCRIPTIONS
The subtitle stream contains a textual description of the video content.
Definition: avformat.h:796
webvtt_read_packet
static int webvtt_read_packet(AVFormatContext *s, AVPacket *pkt)
Definition: webvttdec.c:173
AV_PKT_DATA_WEBVTT_IDENTIFIER
@ AV_PKT_DATA_WEBVTT_IDENTIFIER
The optional first identifier line of a WebVTT cue.
Definition: packet.h:197
options
static const AVOption options[]
Definition: webvttdec.c:197
webvtt_read_close
static int webvtt_read_close(AVFormatContext *s)
Definition: webvttdec.c:187
webvtt_probe
static int webvtt_probe(const AVProbeData *p)
Definition: webvttdec.c:40
subtitles.h
AV_OPT_TYPE_INT
@ AV_OPT_TYPE_INT
Definition: opt.h:225
WebVTTContext::kind
int kind
Definition: webvttdec.c:37
webvtt_read_seek
static int webvtt_read_seek(AVFormatContext *s, int stream_index, int64_t min_ts, int64_t ts, int64_t max_ts, int flags)
Definition: webvttdec.c:179
read_probe
static int read_probe(const AVProbeData *p)
Definition: cdg.c:29
AVCodecParameters::codec_id
enum AVCodecID codec_id
Specific type of the encoded data (the codec used).
Definition: codec_par.h:55
AVPacket
This structure stores compressed data.
Definition: packet.h:499
AVPacket::pos
int64_t pos
byte position in stream, -1 if unknown
Definition: packet.h:542
flags
#define flags(name, subs,...)
Definition: cbs_av1.c:474
AV_RB24
uint64_t_TMPL AV_WL64 unsigned int_TMPL AV_WL32 unsigned int_TMPL AV_WL24 unsigned int_TMPL AV_WL16 uint64_t_TMPL AV_WB64 unsigned int_TMPL AV_WB32 unsigned int_TMPL AV_RB24
Definition: bytestream.h:97
AV_OPT_TYPE_CONST
@ AV_OPT_TYPE_CONST
Definition: opt.h:234
webvtt_read_header
static int webvtt_read_header(AVFormatContext *s)
Definition: webvttdec.c:60