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I also did tests. And with HME results are worse. Video 2000 frames, 3840x1600, HDR. Additional tests a bit later.

no-hme
encoded 2001 frames in 1364.38s (1.47 fps), 10941.58 kb/s, Avg QP:21.73, SSIM Mean Y: 0.9838777 (17.926 dB)

--hme --hme-search umh,umh,star
encoded 2001 frames in 1953.88s (1.02 fps), 10773.71 kb/s, Avg QP:21.80, SSIM Mean Y: 0.9837793 (17.899 dB)

no-hme
encoded 2001 frames in 1373.02s (1.46 fps), 10941.58 kb/s, Avg QP:21.73, Global PSNR: 48.476 (w/o --tune psnr Global PSNR: 48.511)

--hme --hme-search umh,umh,star
encoded 2001 frames in 1886.87s (1.06 fps), 10772.40 kb/s, Avg QP:21.80, Global PSNR: 48.449 (w/o --tune psnr Global PSNR: 48.481)