AppDecode nFrameReturned questions

The demo(video-sdk-samples-master\Samples\AppDecode\AppDecD3D\AppDecD3D.cpp) was slightly modified to realize decoded playback of rtsp video streams.
Found that the pedestrian walking video playing card card card, walking action is not smooth;
The nFrameReturned argument appears from time to time: 0,4;
The problem is when the 0,4 parameter is returned;
How can this situation be optimized? Does the decoder have optimization parameters to configure?