I am using aAVVideoCoreAnimationToolto render titles on top of a video composition.I used to use+videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:inLayer:to instantiate the animation tool.However, I now need to use a custom compositor to render the video composition. I want to usevideoCompositionCoreAnimationToolWithAdditionalLayer:asTrackID:so that I have access to an asset track with the titles in my compositor.However, I can't get titles to render when adding the core animation layer as a track.In my custom compositor I have access to the track, i.e. I can get a pixelBuffer for the trackID I have assigned for the Core Animation layer when instantiating the animation tool. But these pixel buffers are empty.- (void)startVideoCompositionRequest:(AVAsynchronousVideoCompositionRequest *)request { CMPersistentTrackID titleTrackID = ... CVPixelBufferRef titlePixelBuffer = [request sourceFrameByTrackID:titleTrackID]; //titlePixelBuffer is valid pixel buffer but never contains any pixel data }When I set up the core animation tool the same way, but don't use a custom compositor, the title layer also isn't rendered.If I set up the animation tool using+videoCompositionCoreAnimationToolWithPostProcessingAsVideoLayer:inLayer:and don't use a custom compositor the title layer is rendered as it should.Is there anything I'm missing?(I am also adding the sourceTrackID of the title track to the composition's AVVideoCompositionInstruction instances)