noise caused by TX2 ISP

When i use TX2 to capture video with nvcamerasrc, there is significant noise. But when i use v4l2 to capture raw data, there is nearly no noise in the video converted from the raw data. So i think the noise is caused by ISP when using nvcamerasrc. I have thought the ISP digital gain is too high, but there is still obvious noise when i set the ISP digital gain to 1 in argus_camera app. The noise is driving me crazy, i think there must be some wrong or not matched between the isp configuration with camera driver. I have tried the on-board camera and other CSI camera, the result is same.
Could you give me some suggestions?

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