I just tried another encode, ensuring low quants.
And Chroma-qp-offset made an impact on PSNR.
Pass1.
Code:
C:\Program Files\x264>x264.exe --pass 1 --bitrate 2000 --stats "F:\2pass.log" --bframes 2
--b-pyramid --weightb --analyse p8x8,b8x8,i4x4 --chroma-qp-offset 12 --threads 2 --progress --frames 2000 --output NUL
"F:\test.avs"
avis [info]: 704x288 @ 25.00 fps (7063 frames)
x264 [info]: using cpu capabilities MMX MMXEXT SSE SSE2
x264 [info]: slice I:47 Avg QP:15.06 size: 23452 PSNR Mean Y:49.06 U:45.86 V:46.75 Avg:47.88 Global:47.48
x264 [info]: slice P:1225 Avg QP:17.51 size: 12292 PSNR Mean Y:46.29 U:44.57 V:45.45 Avg:45.78 Global:45.47
x264 [info]: slice B:728 Avg QP:18.87 size: 5991 PSNR Mean Y:45.13 U:44.46 V:45.02 Avg:44.95 Global:44.54
x264 [info]: mb I I16..4: 17.3% 0.0% 82.7%
x264 [info]: mb P I16..4: 11.3% 0.0% 26.5% P16..4: 24.1% 21.2% 11.2% 0.0% 0.0% skip: 5.7%
x264 [info]: mb B I16..4: 2.4% 0.0% 5.3% B16..8: 50.1% 5.0% 10.9% direct: 5.9% skip:20.3%
x264 [info]: PSNR Mean Y:45.930 U:44.562 V:45.326 Avg:45.529 Global:45.139 kb/s: 2052.16
encoded 2000 frames, 18.22 fps, 2053.30 kb/s
Pass2.
Code:
C:\Program Files\x264>x264.exe --pass 2 --bitrate 2000 --stats "F:\2pass.log" --bframes 2
--b-pyramid --weightb --analyse p8x8,b8x8,i4x4 --chroma-qp-offset 12 --threads 2 --progress --frames 2000
--output "f:\test1.mkv" "F:\test.avs"
avis [info]: 704x288 @ 25.00 fps (7063 frames)
x264 [info]: using cpu capabilities MMX MMXEXT SSE SSE2
x264 [info]: slice I:47 Avg QP:15.66 size: 21978 PSNR Mean Y:48.69 U:45.71 V:46.50 Avg:47.61 Global:47.37
x264 [info]: slice P:1225 Avg QP:17.49 size: 12149 PSNR Mean Y:46.29 U:44.60 V:45.46 Avg:45.80 Global:45.59
x264 [info]: slice B:728 Avg QP:18.97 size: 5666 PSNR Mean Y:45.08 U:44.40 V:44.88 Avg:44.90 Global:44.66
x264 [info]: mb I I16..4: 18.2% 0.0% 81.8%
x264 [info]: mb P I16..4: 11.6% 0.0% 25.7% P16..4: 25.2% 21.2% 10.4% 0.0% 0.0% skip: 6.1%
x264 [info]: mb B I16..4: 2.2% 0.0% 5.4% B16..8: 50.4% 3.8% 8.3% direct: 6.8% skip:23.2%
x264 [info]: PSNR Mean Y:45.905 U:44.553 V:45.271 Avg:45.513 Global:45.263 kb/s: 2004.07
encoded 2000 frames, 20.34 fps, 2005.21 kb/s