Meet some issues about video/x-raw(memory:NVMM) when use code jetson-utils in github

I use the code jetson_utils in github,video-viewer,simply pull the local 1920x1080 video and play it,but it seems the framerate drops from 24 to about 16 fps.So why this happend and how can I improve the framerate?And afterwards,I change the video/x-raw to video/x-raw(memory:NVMM) in gstdecoder.cpp,the framerate seems to be right.However,the video become a full green video.How to improve the framerate?My device is Jetson Xavier NX.Jetpack version is 4.4.And I have tested in Xavier and TX2,the condition is the same.

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