mutagen/oggspeex.py

   1 # Ogg Speex 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: oggspeex.py 3976 2007-01-13 22:00:14Z piman $
  10
  11 """Read and write Ogg Speex comments.
  12
  13 This module handles Speex files wrapped in an Ogg bitstream. The
  14 first Speex stream found is used.
  15
  16 Read more about Ogg Speex at http://www.speex.org/. This module is
  17 based on the specification at http://www.speex.org/manual2/node7.html
  18 and clarifications after personal communication with Jean-Marc,
  19 http://lists.xiph.org/pipermail/speex-dev/2006-July/004676.html.
  20 """
  21
  22 __all__ = ["OggSpeex", "Open", "delete"]
  23
  24 from mutagen._vorbis import VCommentDict
  25 from mutagen.ogg import OggPage, OggFileType, error as OggError
  26 from mutagen._util import cdata
  27
  28 class error(OggError): pass
  29 class OggSpeexHeaderError(error): pass
  30
  31 class OggSpeexInfo(object):
  32     """Ogg Speex stream information.
  33
  34     Attributes:
  35     bitrate - nominal bitrate in bits per second
  36     channels - number of channels
  37     length - file length in seconds, as a float
  38
  39     The reference encoder does not set the bitrate; in this case,
  40     the bitrate will be 0.
  41     """
  42
  43     length = 0
  44
  45     def __init__(self, fileobj):
  46         page = OggPage(fileobj)
  47         while not page.packets[0].startswith("Speex   "):
  48             page = OggPage(fileobj)
  49         if not page.first:
  50             raise OggSpeexHeaderError(
  51                 "page has ID header, but doesn't start a stream")
  52         self.sample_rate = cdata.uint_le(page.packets[0][36:40])
  53         self.channels = cdata.uint_le(page.packets[0][48:52])
  54         self.bitrate = max(0, cdata.int_le(page.packets[0][52:56]))
  55         self.serial = page.serial
  56
  57     def pprint(self):
  58         return "Ogg Speex, %.2f seconds" % self.length
  59
  60 class OggSpeexVComment(VCommentDict):
  61     """Speex comments embedded in an Ogg bitstream."""
  62
  63     def __init__(self, fileobj, info):
  64         pages = []
  65         complete = False
  66         while not complete:
  67             page = OggPage(fileobj)
  68             if page.serial == info.serial:
  69                 pages.append(page)
  70                 complete = page.complete or (len(page.packets) > 1)
  71         data = OggPage.to_packets(pages)[0] + "\x01"
  72         super(OggSpeexVComment, self).__init__(data, framing=False)
  73
  74     def _inject(self, fileobj):
  75         """Write tag data into the Speex comment packet/page."""
  76
  77         fileobj.seek(0)
  78
  79         # Find the first header page, with the stream info.
  80         # Use it to get the serial number.
  81         page = OggPage(fileobj)
  82         while not page.packets[0].startswith("Speex   "):
  83             page = OggPage(fileobj)
  84
  85         # Look for the next page with that serial number, it'll start
  86         # the comment packet.
  87         serial = page.serial
  88         page = OggPage(fileobj)
  89         while page.serial != serial:
  90             page = OggPage(fileobj)
  91
  92         # Then find all the pages with the comment packet.
  93         old_pages = [page]
  94         while not (old_pages[-1].complete or len(old_pages[-1].packets) > 1):
  95             page = OggPage(fileobj)
  96             if page.serial == old_pages[0].serial:
  97                 old_pages.append(page)
  98
  99         packets = OggPage.to_packets(old_pages, strict=False)
 100
 101         # Set the new comment packet.
 102         packets[0] = self.write(framing=False)
 103
 104         new_pages = OggPage.from_packets(packets, old_pages[0].sequence)
 105         OggPage.replace(fileobj, old_pages, new_pages)
 106
 107 class OggSpeex(OggFileType):
 108     """An Ogg Speex file."""
 109
 110     _Info = OggSpeexInfo
 111     _Tags = OggSpeexVComment
 112     _Error = OggSpeexHeaderError
 113     _mimes = ["audio/x-speex"]
 114
 115     def score(filename, fileobj, header):
 116         return (header.startswith("OggS") * ("Speex   " in header))
 117     score = staticmethod(score)
 118
 119 Open = OggSpeex
 120
 121 def delete(filename):
 122     """Remove tags from a file."""
 123     OggSpeex(filename).delete()