mutagen/oggtheora.py

   1 # Ogg Theora support.
   2 #
   3 # Copyright 2006 Joe Wreschnig
   4 #
   5 # This program is free software; you can redistribute it and/or modify
   6 # it under the terms of the GNU General Public License version 2 as
   7 # published by the Free Software Foundation.
   8 #
   9 # $Id: oggtheora.py 3976 2007-01-13 22:00:14Z piman $
  10
  11 """Read and write Ogg Theora comments.
  12
  13 This module handles Theora files wrapped in an Ogg bitstream. The
  14 first Theora stream found is used.
  15
  16 Based on the specification at http://theora.org/doc/Theora_I_spec.pdf.
  17 """
  18
  19 __all__ = ["OggTheora", "Open", "delete"]
  20
  21 import struct
  22
  23 from mutagen._vorbis import VCommentDict
  24 from mutagen.ogg import OggPage, OggFileType, error as OggError
  25
  26 class error(OggError): pass
  27 class OggTheoraHeaderError(error): pass
  28
  29 class OggTheoraInfo(object):
  30     """Ogg Theora stream information.
  31
  32     Attributes:
  33     length - file length in seconds, as a float
  34     fps - video frames per second, as a float
  35     """
  36
  37     length = 0
  38
  39     def __init__(self, fileobj):
  40         page = OggPage(fileobj)
  41         while not page.packets[0].startswith("\x80theora"):
  42             page = OggPage(fileobj)
  43         if not page.first:
  44             raise OggTheoraHeaderError(
  45                 "page has ID header, but doesn't start a stream")
  46         data = page.packets[0]
  47         vmaj, vmin = struct.unpack("2B", data[7:9])
  48         if (vmaj, vmin) != (3, 2):
  49             raise OggTheoraHeaderError(
  50                 "found Theora version %d.%d != 3.2" % (vmaj, vmin))
  51         fps_num, fps_den = struct.unpack(">2I", data[22:30])
  52         self.fps = fps_num / float(fps_den)
  53         self.bitrate = struct.unpack(">I", data[37:40] + "\x00")[0]
  54         self.serial = page.serial
  55
  56     def pprint(self):
  57         return "Ogg Theora, %.2f seconds, %d bps" % (self.length, self.bitrate)
  58
  59 class OggTheoraCommentDict(VCommentDict):
  60     """Theora comments embedded in an Ogg bitstream."""
  61
  62     def __init__(self, fileobj, info):
  63         pages = []
  64         complete = False
  65         while not complete:
  66             page = OggPage(fileobj)
  67             if page.serial == info.serial:
  68                 pages.append(page)
  69                 complete = page.complete or (len(page.packets) > 1)
  70         data = OggPage.to_packets(pages)[0][7:]
  71         super(OggTheoraCommentDict, self).__init__(data + "\x01")
  72
  73     def _inject(self, fileobj):
  74         """Write tag data into the Theora comment packet/page."""
  75
  76         fileobj.seek(0)
  77         page = OggPage(fileobj)
  78         while not page.packets[0].startswith("\x81theora"):
  79             page = OggPage(fileobj)
  80
  81         old_pages = [page]
  82         while not (old_pages[-1].complete or len(old_pages[-1].packets) > 1):
  83             page = OggPage(fileobj)
  84             if page.serial == old_pages[0].serial:
  85                 old_pages.append(page)
  86
  87         packets = OggPage.to_packets(old_pages, strict=False)
  88
  89         packets[0] = "\x81theora" + self.write(framing=False)
  90
  91         new_pages = OggPage.from_packets(packets, old_pages[0].sequence)
  92         OggPage.replace(fileobj, old_pages, new_pages)
  93
  94 class OggTheora(OggFileType):
  95     """An Ogg Theora file."""
  96
  97     _Info = OggTheoraInfo
  98     _Tags = OggTheoraCommentDict
  99     _Error = OggTheoraHeaderError
 100     _mimes = ["video/x-theora"]
 101
 102     def score(filename, fileobj, header):
 103         return (header.startswith("OggS") *
 104                 (("\x80theora" in header) + ("\x81theora" in header)))
 105     score = staticmethod(score)
 106
 107 Open = OggTheora
 108
 109 def delete(filename):
 110     """Remove tags from a file."""
 111     OggTheora(filename).delete()