Initial Commit

lib/mutagen/oggopus.py

@@ -0,0 +1,138 @@
+# -*- coding: utf-8 -*-
+
+# Copyright (C) 2012, 2013  Christoph Reiter
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation.
+
+"""Read and write Ogg Opus comments.
+
+This module handles Opus files wrapped in an Ogg bitstream. The
+first Opus stream found is used.
+
+Based on http://tools.ietf.org/html/draft-terriberry-oggopus-01
+"""
+
+__all__ = ["OggOpus", "Open", "delete"]
+
+import struct
+
+from mutagen import StreamInfo
+from mutagen._compat import BytesIO
+from mutagen._vorbis import VCommentDict
+from mutagen.ogg import OggPage, OggFileType, error as OggError
+
+
+class error(OggError):
+    pass
+
+
+class OggOpusHeaderError(error):
+    pass
+
+
+class OggOpusInfo(StreamInfo):
+    """Ogg Opus stream information.
+
+    Attributes:
+
+    * length - file length in seconds, as a float
+    * channels - number of channels
+    """
+
+    length = 0
+
+    def __init__(self, fileobj):
+        page = OggPage(fileobj)
+        while not page.packets[0].startswith(b"OpusHead"):
+            page = OggPage(fileobj)
+
+        self.serial = page.serial
+
+        if not page.first:
+            raise OggOpusHeaderError(
+                "page has ID header, but doesn't start a stream")
+
+        (version, self.channels, pre_skip, orig_sample_rate, output_gain,
+         channel_map) = struct.unpack("<BBHIhB", page.packets[0][8:19])
+
+        self.__pre_skip = pre_skip
+
+        # only the higher 4 bits change on incombatible changes
+        major = version >> 4
+        if major != 0:
+            raise OggOpusHeaderError("version %r unsupported" % major)
+
+    def _post_tags(self, fileobj):
+        page = OggPage.find_last(fileobj, self.serial)
+        self.length = (page.position - self.__pre_skip) / float(48000)
+
+    def pprint(self):
+        return u"Ogg Opus, %.2f seconds" % (self.length)
+
+
+class OggOpusVComment(VCommentDict):
+    """Opus comments embedded in an Ogg bitstream."""
+
+    def __get_comment_pages(self, fileobj, info):
+        # find the first tags page with the right serial
+        page = OggPage(fileobj)
+        while ((info.serial != page.serial) or
+                not page.packets[0].startswith(b"OpusTags")):
+            page = OggPage(fileobj)
+
+        # get all comment pages
+        pages = [page]
+        while not (pages[-1].complete or len(pages[-1].packets) > 1):
+            page = OggPage(fileobj)
+            if page.serial == pages[0].serial:
+                pages.append(page)
+
+        return pages
+
+    def __init__(self, fileobj, info):
+        pages = self.__get_comment_pages(fileobj, info)
+        data = OggPage.to_packets(pages)[0][8:]  # Strip OpusTags
+        fileobj = BytesIO(data)
+        super(OggOpusVComment, self).__init__(fileobj, framing=False)
+
+        # in case the LSB of the first byte after v-comment is 1, preserve the
+        # following data
+        padding_flag = fileobj.read(1)
+        if padding_flag and ord(padding_flag) & 0x1:
+            self._pad_data = padding_flag + fileobj.read()
+        else:
+            self._pad_data = b""
+
+    def _inject(self, fileobj):
+        fileobj.seek(0)
+        info = OggOpusInfo(fileobj)
+        old_pages = self.__get_comment_pages(fileobj, info)
+
+        packets = OggPage.to_packets(old_pages)
+        packets[0] = b"OpusTags" + self.write(framing=False) + self._pad_data
+        new_pages = OggPage.from_packets(packets, old_pages[0].sequence)
+        OggPage.replace(fileobj, old_pages, new_pages)
+
+
+class OggOpus(OggFileType):
+    """An Ogg Opus file."""
+
+    _Info = OggOpusInfo
+    _Tags = OggOpusVComment
+    _Error = OggOpusHeaderError
+    _mimes = ["audio/ogg", "audio/ogg; codecs=opus"]
+
+    @staticmethod
+    def score(filename, fileobj, header):
+        return (header.startswith(b"OggS") * (b"OpusHead" in header))
+
+
+Open = OggOpus
+
+
+def delete(filename):
+    """Remove tags from a file."""
+
+    OggOpus(filename).delete()