gsoc-2014
Problems with Gst.Fraction
There is a Fraction class I need to port but I’m facing a few problems.
In gst-0.10, we use it like gst.Fraction(2,4) and we get a <gst.Fraction 1/2> Here’s the details of gst.Fraction :
Type: classobj
String form: gst.Fraction
File: /usr/lib/python2.7/dist-packages/gst-0.10/gst/__init__.py
Init definition: gst.Fraction(self, num, denom=1)
Source:
class Fraction(Value):
def __init__(self, num, denom=1):
def __gcd(a,b):
while b != 0:
tmp = a
a = b
b = tmp % b
return abs(a)
def __simplify():
num = self.num
denom = self.denom
if num < 0:
num = -num
denom = -denom
# Compute greatest common divisor
gcd = __gcd(num,denom)
if gcd != 0:
num /= gcd
denom /= gcd
self.num = num
self.denom = denom
Value.__init__(self, 'fraction')
self.num = num
self.denom = denom
__simplify()
def __repr__(self):
return '<gst.Fraction %d/%d>' % (self.num, self.denom)
def __eq__(self, other):
if isinstance(other, Fraction):
return self.num * other.denom == other.num * self.denom
return False
def __ne__(self, other):
return not self.__eq__(other)
def __mul__(self, other):
if isinstance(other, Fraction):
return Fraction(self.num * other.num,
self.denom * other.denom)
elif isinstance(other, int):
return Fraction(self.num * other, self.denom)
raise TypeError
__rmul__ = __mul__
def __div__(self, other):
if isinstance(other, Fraction):
return Fraction(self.num * other.denom,
self.denom * other.num)
elif isinstance(other, int):
return Fraction(self.num, self.denom * other)
return TypeError
def __rdiv__(self, other):
if isinstance(other, int):
return Fraction(self.denom * other, self.num)
return TypeError
def __float__(self):
return float(self.num) / float(self.denom)Now, gi has some overrides to achieve this functionality. But, this is not available in Gstreamer-1.2.1 (latest version available in Ubuntu 12.04). So, I tried implementing it in this commit. It failed with this error:
Traceback (most recent call last):
File "/home/aps/workspace/gsoc/flumotion-orig/bin/flumotion-manager", line 41, in <module>
from flumotion.common import boot
File "/home/aps/workspace/gsoc/flumotion-orig/flumotion/__init__.py", line 35, in <module>
class Fraction(Gst.Fraction):
File "/usr/lib/python2.7/dist-packages/gi/types.py", line 212, in __init__
super(GObjectMeta, cls).__init__(name, bases, dict_)
File "/usr/lib/python2.7/dist-packages/gi/_gobject/__init__.py", line 65, in __init__
cls._type_register(cls.__dict__)
File "/usr/lib/python2.7/dist-packages/gi/_gobject/__init__.py", line 119, in _type_register
type_register(cls, namespace.get('__gtype_name__'))
TypeError: Error when calling the metaclass bases
argument must be a GObject subclassBut, running Gst.Fraction.__class__ in python shell gives output gi.types.GObjectMeta
Placing the Gst.py file inside /usr/lib/python27/dist-packages/gi/overrides/ fixes the problem but it’s not a good/valid fix.
The only (hackish) way I could think of is writing a function that gives same results (if possible) as Gst.Fraction. If you can think of any idea, please let me know in comments. Thanks!