def __get_source_property(self, prop):
        if self.__source_uses_keyframes():
            try:
                position = self._project.pipeline.get_position()
                start = self.source.props.start
                in_point = self.source.props.in_point
                duration = self.source.props.duration

                # If the position is outside of the clip, take the property
                # value at the start/end (whichever is closer) of the clip.
                source_position = max(0, min(position - start, duration - 1)) + in_point
                value = self.__control_bindings[prop].get_value(source_position)
                res = value is not None
                return res, value
            except PipelineError:
                pass

        return self.source.get_child_property(prop)