when crossfade is set to 1 for [pdp_mix], outlet should return exact copy of middle inlet. Instead [pdp_mix] still tries to mix the left and middle inlet, resulting in slight degradation of the resulting video. Consequently, a feedback loop connecting [pdp_mix] outlet to its middle inlet through a [pdp_del] with crossfade set to 1 will eventually result in a video that is completely black.

This patch adds a trivial copy from the middle inlet to the outlet if the crossfade is set to 1.