Pillow/PIL/MpegImagePlugin.py

#
# The Python Imaging Library.
# $Id$
#
# MPEG file handling
#
# History:
#       95-09-09 fl     Created
#
# Copyright (c) Secret Labs AB 1997.
# Copyright (c) Fredrik Lundh 1995.
#
# See the README file for information on usage and redistribution.
#

__version__ = "0.1"

import Image, ImageFile

#
# Bitstream parser

class BitStream:

    def __init__(self, fp):
        self.fp = fp
        self.bits = 0
        self.bitbuffer = 0

    def next(self):
        return ord(self.fp.read(1))

    def peek(self, bits):
        while self.bits < bits:
            c = self.next()
            if c < 0:
                self.bits = 0
                continue
            self.bitbuffer = (self.bitbuffer << 8) + c
            self.bits = self.bits + 8
        return self.bitbuffer >> (self.bits - bits) & (1L << bits) - 1

    def skip(self, bits):
        while self.bits < bits:
            self.bitbuffer = (self.bitbuffer << 8) + ord(self.fp.read(1))
            self.bits = self.bits + 8
        self.bits = self.bits - bits

    def read(self, bits):
        v = self.peek(bits)
        self.bits = self.bits - bits
        return v

##
# Image plugin for MPEG streams.  This plugin can identify a stream,
# but it cannot read it.

class MpegImageFile(ImageFile.ImageFile):

    format = "MPEG"
    format_description = "MPEG"

    def _open(self):

        s = BitStream(self.fp)

        if s.read(32) != 0x1B3:
            raise SyntaxError("not an MPEG file")

        self.mode = "RGB"
        self.size = s.read(12), s.read(12)


# --------------------------------------------------------------------
# Registry stuff

Image.register_open("MPEG", MpegImageFile)

Image.register_extension("MPEG", ".mpg")
Image.register_extension("MPEG", ".mpeg")

Image.register_mime("MPEG", "video/mpeg")