Adding upstream version 2024.03.10.upstream/2024.03.10

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 399 insertions, 0 deletions

diff --git a/yt_dlp/webvtt.py b/yt_dlp/webvtt.py
new file mode 100644
index 0000000..7683bfb
--- /dev/null
+++ b/yt_dlp/webvtt.py
@@ -0,0 +1,399 @@
+"""
+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 io
+import re
+
+from .utils import int_or_none, timetuple_from_msec
+
+
+class _MatchParser:
+    """
+    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, re.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, re.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().__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().__init__("Parse error at position %u (near %r)" % (
+            parser._pos, parser._data[parser._pos:parser._pos + 100]
+        ))
+
+
+# While the specification <https://www.w3.org/TR/webvtt1/#webvtt-timestamp>
+# prescribes that hours must be *2 or more* digits, timestamps with a single
+# digit for the hour part has been seen in the wild.
+# See https://github.com/yt-dlp/yt-dlp/issues/921
+_REGEX_TS = re.compile(r'''(?x)
+    (?:([0-9]{1,}):)?
+    ([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])+')
+_REGEX_OPTIONAL_WHITESPACE = re.compile(r'[ \t]*')
+
+
+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.
+    """
+    return 90 * sum(
+        int(part or 0) * mult for part, mult in zip(ts.groups(), (3600_000, 60_000, 1000, 1)))
+
+
+def _format_ts(ts):
+    """
+    Convert an MPEG PES timestamp into a WebVTT timestamp.
+    This will lose sub-millisecond precision.
+    """
+    return '%02u:%02u:%02u.%03u' % timetuple_from_msec(int((ts + 45) // 90))
+
+
+class Block:
+    """
+    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]+)')
+    _REGEX_TSMAP_SEP = re.compile(r'[ \t]*,[ \t]*')
+
+    # This was removed from the spec in the 2017 revision;
+    # the last spec draft to describe this syntax element is
+    # <https://www.w3.org/TR/2015/WD-webvtt1-20151208/#webvtt-metadata-header>.
+    # Nevertheless, YouTube keeps serving those
+    _REGEX_META = re.compile(r'(?:(?!-->)[^\r\n])+:(?:(?!-->)[^\r\n])+(?:\r\n|[\r\n])')
+
+    @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(cls._REGEX_TSMAP_SEP):
+                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, meta = None, None, ''
+        while not parser.consume(_REGEX_NL):
+            if parser.consume(cls._REGEX_TSMAP):
+                local, mpegts = cls.__parse_tsmap(parser)
+                continue
+            m = parser.consume(cls._REGEX_META)
+            if m:
+                meta += m.group(0)
+                continue
+            raise ParseError(parser)
+        parser.commit()
+        return cls(extra=extra, mpegts=mpegts, local=local, meta=meta)
+
+    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')
+        if self.meta:
+            stream.write(self.meta)
+        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)
+        parser.consume(_REGEX_OPTIONAL_WHITESPACE)
+        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')
+
+    @property
+    def as_json(self):
+        return {
+            'id': self.id,
+            'start': self.start,
+            'end': self.end,
+            'text': self.text,
+            'settings': self.settings,
+        }
+
+    def __eq__(self, other):
+        return self.as_json == other.as_json
+
+    @classmethod
+    def from_json(cls, json):
+        return cls(
+            id=json['id'],
+            start=json['start'],
+            end=json['end'],
+            text=json['text'],
+            settings=json['settings']
+        )
+
+    def hinges(self, other):
+        if self.text != other.text:
+            return False
+        if self.settings != other.settings:
+            return False
+        return self.start <= self.end == other.start <= other.end
+
+
+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())
+
+    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)