]>
jfr.im git - yt-dlp.git/blob - yt_dlp/webvtt.py
2 A partial parser for WebVTT segments. Interprets enough of the WebVTT stream
3 to be able to assemble a single stand-alone subtitle file, suitably adjusting
4 timestamps on the way, while everything else is passed through unmodified.
6 Regular expressions based on the W3C WebVTT specification
7 <https://www.w3.org/TR/webvtt1/>. The X-TIMESTAMP-MAP extension is described
8 in RFC 8216 §3.5 <https://tools.ietf.org/html/rfc8216#section-3.5>.
14 from .utils
import int_or_none
, timetuple_from_msec
19 An object that maintains the current parsing position and allows
20 conveniently advancing it as syntax elements are successfully parsed.
23 def __init__(self
, string
):
28 if isinstance(r
, re
.Pattern
):
29 return r
.match(self
._data
, self
._pos
)
30 if isinstance(r
, str):
31 if self
._data
.startswith(r
, self
._pos
):
36 def advance(self
, by
):
39 elif isinstance(by
, re
.Match
):
40 amt
= len(by
.group(0))
41 elif isinstance(by
, str):
43 elif isinstance(by
, int):
51 return self
.advance(self
.match(r
))
54 return _MatchChildParser(self
)
57 class _MatchChildParser(_MatchParser
):
59 A child parser state, which advances through the same data as
60 its parent, but has an independent position. This is useful when
61 advancing through syntax elements we might later want to backtrack
65 def __init__(self
, parent
):
66 super().__init
__(parent
._data
)
67 self
.__parent
= parent
68 self
._pos
= parent
._pos
72 Advance the parent state to the current position of this child state.
74 self
.__parent
._pos
= self
._pos
78 class ParseError(Exception):
79 def __init__(self
, parser
):
80 super().__init
__("Parse error at position %u (near %r)" % (
81 parser
._pos
, parser
._data
[parser
._pos
:parser
._pos
+ 20]
85 # While the specification <https://www.w3.org/TR/webvtt1/#webvtt-timestamp>
86 # prescribes that hours must be *2 or more* digits, timestamps with a single
87 # digit for the hour part has been seen in the wild.
88 # See https://github.com/yt-dlp/yt-dlp/issues/921
89 _REGEX_TS
= re
.compile(r
'''(?x)
95 _REGEX_EOF
= re
.compile(r
'\Z')
96 _REGEX_NL
= re
.compile(r
'(?:\r\n|[\r\n])')
97 _REGEX_BLANK
= re
.compile(r
'(?:\r\n|[\r\n])+')
102 Convert a parsed WebVTT timestamp (a re.Match obtained from _REGEX_TS)
103 into an MPEG PES timestamp: a tick counter at 90 kHz resolution.
106 int(part
or 0) * mult
for part
, mult
in zip(ts
.groups(), (3600_000, 60_000, 1000, 1)))
111 Convert an MPEG PES timestamp into a WebVTT timestamp.
112 This will lose sub-millisecond precision.
114 return '%02u:%02u:%02u.%03u' % timetuple_from_msec(int((ts
+ 45) // 90))
119 An abstract WebVTT block.
122 def __init__(self
, **kwargs
):
123 for key
, val
in kwargs
.items():
124 setattr(self
, key
, val
)
127 def parse(cls
, parser
):
128 m
= parser
.match(cls
._REGEX
)
132 return cls(raw
=m
.group(0))
134 def write_into(self
, stream
):
135 stream
.write(self
.raw
)
138 class HeaderBlock(Block
):
140 A WebVTT block that may only appear in the header part of the file,
141 i.e. before any cue blocks.
147 class Magic(HeaderBlock
):
148 _REGEX
= re
.compile(r
'\ufeff?WEBVTT([ \t][^\r\n]*)?(?:\r\n|[\r\n])')
150 # XXX: The X-TIMESTAMP-MAP extension is described in RFC 8216 §3.5
151 # <https://tools.ietf.org/html/rfc8216#section-3.5>, but the RFC
152 # doesn’t specify the exact grammar nor where in the WebVTT
153 # syntax it should be placed; the below has been devised based
154 # on usage in the wild
156 # And strictly speaking, the presence of this extension violates
157 # the W3C WebVTT spec. Oh well.
159 _REGEX_TSMAP
= re
.compile(r
'X-TIMESTAMP-MAP=')
160 _REGEX_TSMAP_LOCAL
= re
.compile(r
'LOCAL:')
161 _REGEX_TSMAP_MPEGTS
= re
.compile(r
'MPEGTS:([0-9]+)')
162 _REGEX_TSMAP_SEP
= re
.compile(r
'[ \t]*,[ \t]*')
164 # This was removed from the spec in the 2017 revision;
165 # the last spec draft to describe this syntax element is
166 # <https://www.w3.org/TR/2015/WD-webvtt1-20151208/#webvtt-metadata-header>.
167 # Nevertheless, YouTube keeps serving those
168 _REGEX_META
= re
.compile(r
'(?:(?!-->)[^\r\n])+:(?:(?!-->)[^\r\n])+(?:\r\n|[\r\n])')
171 def __parse_tsmap(cls
, parser
):
172 parser
= parser
.child()
175 m
= parser
.consume(cls
._REGEX
_TSMAP
_LOCAL
)
177 m
= parser
.consume(_REGEX_TS
)
179 raise ParseError(parser
)
182 raise ParseError(parser
)
184 m
= parser
.consume(cls
._REGEX
_TSMAP
_MPEGTS
)
186 mpegts
= int_or_none(m
.group(1))
188 raise ParseError(parser
)
190 raise ParseError(parser
)
191 if parser
.consume(cls
._REGEX
_TSMAP
_SEP
):
193 if parser
.consume(_REGEX_NL
):
195 raise ParseError(parser
)
201 def parse(cls
, parser
):
202 parser
= parser
.child()
204 m
= parser
.consume(cls
._REGEX
)
206 raise ParseError(parser
)
209 local
, mpegts
, meta
= None, None, ''
210 while not parser
.consume(_REGEX_NL
):
211 if parser
.consume(cls
._REGEX
_TSMAP
):
212 local
, mpegts
= cls
.__parse
_tsmap
(parser
)
214 m
= parser
.consume(cls
._REGEX
_META
)
218 raise ParseError(parser
)
220 return cls(extra
=extra
, mpegts
=mpegts
, local
=local
, meta
=meta
)
222 def write_into(self
, stream
):
223 stream
.write('WEBVTT')
224 if self
.extra
is not None:
225 stream
.write(self
.extra
)
227 if self
.local
or self
.mpegts
:
228 stream
.write('X-TIMESTAMP-MAP=LOCAL:')
229 stream
.write(_format_ts(self
.local
if self
.local
is not None else 0))
230 stream
.write(',MPEGTS:')
231 stream
.write(str(self
.mpegts
if self
.mpegts
is not None else 0))
234 stream
.write(self
.meta
)
238 class StyleBlock(HeaderBlock
):
239 _REGEX
= re
.compile(r
'''(?x)
240 STYLE[\ \t]*(?:\r\n|[\r\n])
241 ((?:(?!-->)[^\r\n])+(?:\r\n|[\r\n]))*
246 class RegionBlock(HeaderBlock
):
247 _REGEX
= re
.compile(r
'''(?x)
249 ((?:(?!-->)[^\r\n])+(?:\r\n|[\r\n]))*
254 class CommentBlock(Block
):
255 _REGEX
= re
.compile(r
'''(?x)
256 NOTE(?:\r\n|[\ \t\r\n])
257 ((?:(?!-->)[^\r\n])+(?:\r\n|[\r\n]))*
262 class CueBlock(Block
):
264 A cue block. The payload is not interpreted.
267 _REGEX_ID
= re
.compile(r
'((?:(?!-->)[^\r\n])+)(?:\r\n|[\r\n])')
268 _REGEX_ARROW
= re
.compile(r
'[ \t]+-->[ \t]+')
269 _REGEX_SETTINGS
= re
.compile(r
'[ \t]+((?:(?!-->)[^\r\n])+)')
270 _REGEX_PAYLOAD
= re
.compile(r
'[^\r\n]+(?:\r\n|[\r\n])?')
273 def parse(cls
, parser
):
274 parser
= parser
.child()
277 m
= parser
.consume(cls
._REGEX
_ID
)
281 m0
= parser
.consume(_REGEX_TS
)
284 if not parser
.consume(cls
._REGEX
_ARROW
):
286 m1
= parser
.consume(_REGEX_TS
)
289 m2
= parser
.consume(cls
._REGEX
_SETTINGS
)
290 if not parser
.consume(_REGEX_NL
):
293 start
= _parse_ts(m0
)
295 settings
= m2
.group(1) if m2
is not None else None
299 m
= parser
.consume(cls
._REGEX
_PAYLOAD
)
302 text
.write(m
.group(0))
307 start
=start
, end
=end
, settings
=settings
,
311 def write_into(self
, stream
):
312 if self
.id is not None:
313 stream
.write(self
.id)
315 stream
.write(_format_ts(self
.start
))
316 stream
.write(' --> ')
317 stream
.write(_format_ts(self
.end
))
318 if self
.settings
is not None:
320 stream
.write(self
.settings
)
322 stream
.write(self
.text
)
332 'settings': self
.settings
,
335 def __eq__(self
, other
):
336 return self
.as_json
== other
.as_json
339 def from_json(cls
, json
):
345 settings
=json
['settings']
348 def hinges(self
, other
):
349 if self
.text
!= other
.text
:
351 if self
.settings
!= other
.settings
:
353 return self
.start
<= self
.end
== other
.start
<= other
.end
356 def parse_fragment(frag_content
):
358 A generator that yields (partially) parsed WebVTT blocks when given
359 a bytes object containing the raw contents of a WebVTT file.
362 parser
= _MatchParser(frag_content
.decode())
364 yield Magic
.parse(parser
)
366 while not parser
.match(_REGEX_EOF
):
367 if parser
.consume(_REGEX_BLANK
):
370 block
= RegionBlock
.parse(parser
)
374 block
= StyleBlock
.parse(parser
)
378 block
= CommentBlock
.parse(parser
)
380 yield block
# XXX: or skip
385 while not parser
.match(_REGEX_EOF
):
386 if parser
.consume(_REGEX_BLANK
):
389 block
= CommentBlock
.parse(parser
)
391 yield block
# XXX: or skip
393 block
= CueBlock
.parse(parser
)
398 raise ParseError(parser
)