mirror of
https://github.com/yt-dlp/yt-dlp.git
synced 2025-10-31 06:35:12 +00:00
[downloader/hls] Assemble single-file WebVTT subtitles from HLS segments
This commit is contained in:
Felix S
368
yt_dlp/webvtt.py
Normal file
368
yt_dlp/webvtt.py
Normal file
@@ -0,0 +1,368 @@
|
||||
# coding: utf-8
|
||||
from __future__ import unicode_literals, print_function, division
|
||||
|
||||
"""
|
||||
A partial parser for WebVTT segments. Interprets enough of the WebVTT stream
|
||||
to be able to assemble a single stand-alone subtitle file, suitably adjusting
|
||||
timestamps on the way, while everything else is passed through unmodified.
|
||||
|
||||
Regular expressions based on the W3C WebVTT specification
|
||||
<https://www.w3.org/TR/webvtt1/>. The X-TIMESTAMP-MAP extension is described
|
||||
in RFC 8216 §3.5 <https://tools.ietf.org/html/rfc8216#section-3.5>.
|
||||
"""
|
||||
|
||||
import re
|
||||
import io
|
||||
from .utils import int_or_none
|
||||
from .compat import (
|
||||
compat_str as str,
|
||||
compat_Pattern,
|
||||
compat_Match,
|
||||
)
|
||||
|
||||
|
||||
class _MatchParser(object):
|
||||
"""
|
||||
An object that maintains the current parsing position and allows
|
||||
conveniently advancing it as syntax elements are successfully parsed.
|
||||
"""
|
||||
|
||||
def __init__(self, string):
|
||||
self._data = string
|
||||
self._pos = 0
|
||||
|
||||
def match(self, r):
|
||||
if isinstance(r, compat_Pattern):
|
||||
return r.match(self._data, self._pos)
|
||||
if isinstance(r, str):
|
||||
if self._data.startswith(r, self._pos):
|
||||
return len(r)
|
||||
return None
|
||||
raise ValueError(r)
|
||||
|
||||
def advance(self, by):
|
||||
if by is None:
|
||||
amt = 0
|
||||
elif isinstance(by, compat_Match):
|
||||
amt = len(by.group(0))
|
||||
elif isinstance(by, str):
|
||||
amt = len(by)
|
||||
elif isinstance(by, int):
|
||||
amt = by
|
||||
else:
|
||||
raise ValueError(by)
|
||||
self._pos += amt
|
||||
return by
|
||||
|
||||
def consume(self, r):
|
||||
return self.advance(self.match(r))
|
||||
|
||||
def child(self):
|
||||
return _MatchChildParser(self)
|
||||
|
||||
|
||||
class _MatchChildParser(_MatchParser):
|
||||
"""
|
||||
A child parser state, which advances through the same data as
|
||||
its parent, but has an independent position. This is useful when
|
||||
advancing through syntax elements we might later want to backtrack
|
||||
from.
|
||||
"""
|
||||
|
||||
def __init__(self, parent):
|
||||
super(_MatchChildParser, self).__init__(parent._data)
|
||||
self.__parent = parent
|
||||
self._pos = parent._pos
|
||||
|
||||
def commit(self):
|
||||
"""
|
||||
Advance the parent state to the current position of this child state.
|
||||
"""
|
||||
self.__parent._pos = self._pos
|
||||
return self.__parent
|
||||
|
||||
|
||||
class ParseError(Exception):
|
||||
def __init__(self, parser):
|
||||
super(ParseError, self).__init__("Parse error at position %u (near %r)" % (
|
||||
parser._pos, parser._data[parser._pos:parser._pos + 20]
|
||||
))
|
||||
|
||||
|
||||
_REGEX_TS = re.compile(r'''(?x)
|
||||
(?:([0-9]{2,}):)?
|
||||
([0-9]{2}):
|
||||
([0-9]{2})\.
|
||||
([0-9]{3})?
|
||||
''')
|
||||
_REGEX_EOF = re.compile(r'\Z')
|
||||
_REGEX_NL = re.compile(r'(?:\r\n|[\r\n])')
|
||||
_REGEX_BLANK = re.compile(r'(?:\r\n|[\r\n])+')
|
||||
|
||||
|
||||
def _parse_ts(ts):
|
||||
"""
|
||||
Convert a parsed WebVTT timestamp (a re.Match obtained from _REGEX_TS)
|
||||
into an MPEG PES timestamp: a tick counter at 90 kHz resolution.
|
||||
"""
|
||||
|
||||
h, min, s, ms = ts.groups()
|
||||
return 90 * (
|
||||
int(h or 0) * 3600000 + # noqa: W504,E221,E222
|
||||
int(min) * 60000 + # noqa: W504,E221,E222
|
||||
int(s) * 1000 + # noqa: W504,E221,E222
|
||||
int(ms) # noqa: W504,E221,E222
|
||||
)
|
||||
|
||||
|
||||
def _format_ts(ts):
|
||||
"""
|
||||
Convert an MPEG PES timestamp into a WebVTT timestamp.
|
||||
This will lose sub-millisecond precision.
|
||||
"""
|
||||
|
||||
ts = int((ts + 45) // 90)
|
||||
ms , ts = divmod(ts, 1000) # noqa: W504,E221,E222,E203
|
||||
s , ts = divmod(ts, 60) # noqa: W504,E221,E222,E203
|
||||
min, h = divmod(ts, 60) # noqa: W504,E221,E222
|
||||
return '%02u:%02u:%02u.%03u' % (h, min, s, ms)
|
||||
|
||||
|
||||
class Block(object):
|
||||
"""
|
||||
An abstract WebVTT block.
|
||||
"""
|
||||
|
||||
def __init__(self, **kwargs):
|
||||
for key, val in kwargs.items():
|
||||
setattr(self, key, val)
|
||||
|
||||
@classmethod
|
||||
def parse(cls, parser):
|
||||
m = parser.match(cls._REGEX)
|
||||
if not m:
|
||||
return None
|
||||
parser.advance(m)
|
||||
return cls(raw=m.group(0))
|
||||
|
||||
def write_into(self, stream):
|
||||
stream.write(self.raw)
|
||||
|
||||
|
||||
class HeaderBlock(Block):
|
||||
"""
|
||||
A WebVTT block that may only appear in the header part of the file,
|
||||
i.e. before any cue blocks.
|
||||
"""
|
||||
|
||||
pass
|
||||
|
||||
|
||||
class Magic(HeaderBlock):
|
||||
_REGEX = re.compile(r'\ufeff?WEBVTT([ \t][^\r\n]*)?(?:\r\n|[\r\n])')
|
||||
|
||||
# XXX: The X-TIMESTAMP-MAP extension is described in RFC 8216 §3.5
|
||||
# <https://tools.ietf.org/html/rfc8216#section-3.5>, but the RFC
|
||||
# doesn’t specify the exact grammar nor where in the WebVTT
|
||||
# syntax it should be placed; the below has been devised based
|
||||
# on usage in the wild
|
||||
#
|
||||
# And strictly speaking, the presence of this extension violates
|
||||
# the W3C WebVTT spec. Oh well.
|
||||
|
||||
_REGEX_TSMAP = re.compile(r'X-TIMESTAMP-MAP=')
|
||||
_REGEX_TSMAP_LOCAL = re.compile(r'LOCAL:')
|
||||
_REGEX_TSMAP_MPEGTS = re.compile(r'MPEGTS:([0-9]+)')
|
||||
|
||||
@classmethod
|
||||
def __parse_tsmap(cls, parser):
|
||||
parser = parser.child()
|
||||
|
||||
while True:
|
||||
m = parser.consume(cls._REGEX_TSMAP_LOCAL)
|
||||
if m:
|
||||
m = parser.consume(_REGEX_TS)
|
||||
if m is None:
|
||||
raise ParseError(parser)
|
||||
local = _parse_ts(m)
|
||||
if local is None:
|
||||
raise ParseError(parser)
|
||||
else:
|
||||
m = parser.consume(cls._REGEX_TSMAP_MPEGTS)
|
||||
if m:
|
||||
mpegts = int_or_none(m.group(1))
|
||||
if mpegts is None:
|
||||
raise ParseError(parser)
|
||||
else:
|
||||
raise ParseError(parser)
|
||||
if parser.consume(','):
|
||||
continue
|
||||
if parser.consume(_REGEX_NL):
|
||||
break
|
||||
raise ParseError(parser)
|
||||
|
||||
parser.commit()
|
||||
return local, mpegts
|
||||
|
||||
@classmethod
|
||||
def parse(cls, parser):
|
||||
parser = parser.child()
|
||||
|
||||
m = parser.consume(cls._REGEX)
|
||||
if not m:
|
||||
raise ParseError(parser)
|
||||
|
||||
extra = m.group(1)
|
||||
local, mpegts = None, None
|
||||
if parser.consume(cls._REGEX_TSMAP):
|
||||
local, mpegts = cls.__parse_tsmap(parser)
|
||||
if not parser.consume(_REGEX_NL):
|
||||
raise ParseError(parser)
|
||||
parser.commit()
|
||||
return cls(extra=extra, mpegts=mpegts, local=local)
|
||||
|
||||
def write_into(self, stream):
|
||||
stream.write('WEBVTT')
|
||||
if self.extra is not None:
|
||||
stream.write(self.extra)
|
||||
stream.write('\n')
|
||||
if self.local or self.mpegts:
|
||||
stream.write('X-TIMESTAMP-MAP=LOCAL:')
|
||||
stream.write(_format_ts(self.local if self.local is not None else 0))
|
||||
stream.write(',MPEGTS:')
|
||||
stream.write(str(self.mpegts if self.mpegts is not None else 0))
|
||||
stream.write('\n')
|
||||
stream.write('\n')
|
||||
|
||||
|
||||
class StyleBlock(HeaderBlock):
|
||||
_REGEX = re.compile(r'''(?x)
|
||||
STYLE[\ \t]*(?:\r\n|[\r\n])
|
||||
((?:(?!-->)[^\r\n])+(?:\r\n|[\r\n]))*
|
||||
(?:\r\n|[\r\n])
|
||||
''')
|
||||
|
||||
|
||||
class RegionBlock(HeaderBlock):
|
||||
_REGEX = re.compile(r'''(?x)
|
||||
REGION[\ \t]*
|
||||
((?:(?!-->)[^\r\n])+(?:\r\n|[\r\n]))*
|
||||
(?:\r\n|[\r\n])
|
||||
''')
|
||||
|
||||
|
||||
class CommentBlock(Block):
|
||||
_REGEX = re.compile(r'''(?x)
|
||||
NOTE(?:\r\n|[\ \t\r\n])
|
||||
((?:(?!-->)[^\r\n])+(?:\r\n|[\r\n]))*
|
||||
(?:\r\n|[\r\n])
|
||||
''')
|
||||
|
||||
|
||||
class CueBlock(Block):
|
||||
"""
|
||||
A cue block. The payload is not interpreted.
|
||||
"""
|
||||
|
||||
_REGEX_ID = re.compile(r'((?:(?!-->)[^\r\n])+)(?:\r\n|[\r\n])')
|
||||
_REGEX_ARROW = re.compile(r'[ \t]+-->[ \t]+')
|
||||
_REGEX_SETTINGS = re.compile(r'[ \t]+((?:(?!-->)[^\r\n])+)')
|
||||
_REGEX_PAYLOAD = re.compile(r'[^\r\n]+(?:\r\n|[\r\n])?')
|
||||
|
||||
@classmethod
|
||||
def parse(cls, parser):
|
||||
parser = parser.child()
|
||||
|
||||
id = None
|
||||
m = parser.consume(cls._REGEX_ID)
|
||||
if m:
|
||||
id = m.group(1)
|
||||
|
||||
m0 = parser.consume(_REGEX_TS)
|
||||
if not m0:
|
||||
return None
|
||||
if not parser.consume(cls._REGEX_ARROW):
|
||||
return None
|
||||
m1 = parser.consume(_REGEX_TS)
|
||||
if not m1:
|
||||
return None
|
||||
m2 = parser.consume(cls._REGEX_SETTINGS)
|
||||
if not parser.consume(_REGEX_NL):
|
||||
return None
|
||||
|
||||
start = _parse_ts(m0)
|
||||
end = _parse_ts(m1)
|
||||
settings = m2.group(1) if m2 is not None else None
|
||||
|
||||
text = io.StringIO()
|
||||
while True:
|
||||
m = parser.consume(cls._REGEX_PAYLOAD)
|
||||
if not m:
|
||||
break
|
||||
text.write(m.group(0))
|
||||
|
||||
parser.commit()
|
||||
return cls(
|
||||
id=id,
|
||||
start=start, end=end, settings=settings,
|
||||
text=text.getvalue()
|
||||
)
|
||||
|
||||
def write_into(self, stream):
|
||||
if self.id is not None:
|
||||
stream.write(self.id)
|
||||
stream.write('\n')
|
||||
stream.write(_format_ts(self.start))
|
||||
stream.write(' --> ')
|
||||
stream.write(_format_ts(self.end))
|
||||
if self.settings is not None:
|
||||
stream.write(' ')
|
||||
stream.write(self.settings)
|
||||
stream.write('\n')
|
||||
stream.write(self.text)
|
||||
stream.write('\n')
|
||||
|
||||
|
||||
def parse_fragment(frag_content):
|
||||
"""
|
||||
A generator that yields (partially) parsed WebVTT blocks when given
|
||||
a bytes object containing the raw contents of a WebVTT file.
|
||||
"""
|
||||
|
||||
parser = _MatchParser(frag_content.decode('utf-8'))
|
||||
|
||||
yield Magic.parse(parser)
|
||||
|
||||
while not parser.match(_REGEX_EOF):
|
||||
if parser.consume(_REGEX_BLANK):
|
||||
continue
|
||||
|
||||
block = RegionBlock.parse(parser)
|
||||
if block:
|
||||
yield block
|
||||
continue
|
||||
block = StyleBlock.parse(parser)
|
||||
if block:
|
||||
yield block
|
||||
continue
|
||||
block = CommentBlock.parse(parser)
|
||||
if block:
|
||||
yield block # XXX: or skip
|
||||
continue
|
||||
|
||||
break
|
||||
|
||||
while not parser.match(_REGEX_EOF):
|
||||
if parser.consume(_REGEX_BLANK):
|
||||
continue
|
||||
|
||||
block = CommentBlock.parse(parser)
|
||||
if block:
|
||||
yield block # XXX: or skip
|
||||
continue
|
||||
block = CueBlock.parse(parser)
|
||||
if block:
|
||||
yield block
|
||||
continue
|
||||
|
||||
raise ParseError(parser)
|
||||
Reference in New Issue
Block a user