This correction ensures a consistent use of 'ref' and 'unref' for paints to release memory properly.
The memory leak occurred when a picture was not pushed to a valid canvas.
This issue was reported by the unit-test memory sanitizer.
migrate transform from the group to the layer.
transformation is not necessary in group but layer.
This helps to reduce the unnecessary assigning of the transformation
in group instances.
To achieve full threading efficiency,
the header should return the necessary properties:
view size, framerate, and duration.
This commit adds duration parsing.
Also don't do the header task in case of single thread
because there wouldn't be parallel effects.
