H.265 encode performance on TX2

I try to encode 4K YUV video (original) to H.265 stream by Multimedia API, and decode the H.265 stream to 4K YUV video (compressed), the PSNR performance is not distinguished compared with H.264.

Our procedures are the following, the PSNR results is close to H.264, Is it correct on TX2 ?

Step1. prepare the 4K YUV420 video sequence.
The source video is from http://ultravideo.cs.tut.fi/#testsequences.

Step2. H.265/H.264 Video encode command as bellow, and various bitrates are 20M, 10M, 6M, and 2Mbps.
./video_cuda_enc ShakeNDry_3840x2160.yuv 3840 2160 H265 ShakeNDry.h265 -br 20000000 -fps 30 1
./video_cuda_enc ShakeNDry_3840x2160.yuv 3840 2160 H264 ShakeNDry.h264 -br 20000000 -fps 30 1

Step3. H.265/H.264 Video decode as bellow.
./video_dec_cuda ShakeNDry.h265 3840 2160 H265 -o ShakeNDry_265.yuv -fps 30 1 -f 2
./video_dec_cuda ShakeNDry.h264 3840 2160 H264 -o ShakeNDry_264.yuv -fps 30 1 -f 2

Step4. Read the original video and compressed video, and test the PSNR quality of different H.265/264 encoders.
The example code is from https://ch.mathworks.com/matlabcentral/fileexchange/12455-psnr-of-yuv-videos

Step5. The results are follows.
Bitrate H.265_coded+bits H.265_PSNR H.265_Coded+bits H.264_PSNR
20Mbps 25.4MB 38.75dB 25.0MB 38.41dB
10Mbps 12.7MB 37.29dB 12.3MB 36.85dB
6Mbps 7.5MB 36.28dB 7.3MB 35.72dB
2Mbps 2.3MB 35.21dB 2.2MB 34.36dB

Hi,
We are not able to explain more about your comparison. It is about design of HW video filters.

Encoding performance and video quality are tradeoffs. If you require better quality, please configure

"-hpt <type>           HW preset type (1 = ultrafast, 2 = fast, 3 = medium,  4 = slow)"