ffmpeg mediocre conversion quality from DVD

I am trying to convert a DVD that I own into mp4/lib265 format. To test the quality out I am only converting the first two minutes of the input video (which is a concatenated vob file). The source video is not particularly high resolution being a DVD it is 720x480

  • I tried 8/10/12 bit hevc
  • For a 720p video I usually go crf-22 and for 1080p crf-20 and usually happy with these values. This dvd is lower resolution than that, I tried going as low as crf-18
  • I use min-keyint and keyint parameters always, as I keep them very low to increase seeking performance. These being low enough should not decrease quality but I tried with even lower min-keyint just in case.

Problem: In the video whenever camera moves, I can see huge pixels across all details on screen. The camera movement is not even particularly fast. For example it moves from the belt level of the main character to face in approximately 2 seconds.

Question:
Can someone possibly point out what I am doing wrong or what else to do, to fix this. or may be some fine tuning parameters?

Command ran for testing:

ffmpeg ^
-i "ConCat2.vob" ^
-ss 00:00:00 -to 00:02:00 -c:v libx265 -c:a aac -x265-params  "crf=20:min-keyint=5:keyint=50"  -preset slow -map 0:1 -map 0:2 "08 bit.crf20.ki05.mp4"  ^
-ss 00:00:00 -to 00:02:00 -c:v libx265 -c:a aac -x265-params  "crf=20:min-keyint=5:keyint=50"  -preset slow -pix_fmt yuv420p10le -map 0:1 -map 0:2 "10 bit.crf20.ki05.mp4" ^
-ss 00:00:00 -to 00:02:00 -c:v libx265 -c:a aac -x265-params  "crf=20:min-keyint=5:keyint=50"  -preset slow -pix_fmt yuv420p12le -map 0:1 -map 0:2 "12 bit.crf20.ki05.mp4" ^
-ss 00:00:00 -to 00:02:00 -c:v libx265 -c:a aac -x265-params  "crf=20:min-keyint=25:keyint=50" -preset slow -map 0:1 -map 0:2 "08 bit.crf20.ki25.mp4" ^
-ss 00:00:00 -to 00:02:00 -c:v libx265 -c:a aac -x265-params  "crf=20:min-keyint=25:keyint=50" -preset slow -pix_fmt yuv420p10le -map 0:1 -map 0:2 "10 bit.crf20.ki25.mp4" ^
-ss 00:00:00 -to 00:02:00 -c:v libx265 -c:a aac -x265-params  "crf=20:min-keyint=25:keyint=50" -preset slow -pix_fmt yuv420p12le -map 0:1 -map 0:2 "12 bit.crf20.ki25.mp4" ^
-ss 00:00:00 -to 00:02:00 -c:v libx265 -c:a aac -x265-params  "crf=18:min-keyint=25:keyint=50" -preset slow -map 0:1 -map 0:2 "08 bit.crf18.ki25.mp4" ^
-ss 00:00:00 -to 00:02:00 -c:v libx265 -c:a aac -x265-params  "crf=18:min-keyint=25:keyint=50" -preset slow -pix_fmt yuv420p10le -map 0:1 -map 0:2 "10 bit.crf18.ki25.mp4" ^
-ss 00:00:00 -to 00:02:00 -c:v libx265 -c:a aac -x265-params  "crf=18:min-keyint=25:keyint=50" -preset slow -pix_fmt yuv420p12le -map 0:1 -map 0:2 "12 bit.crf18.ki25.mp4"

ffprobe for input:

ffprobe version 4.3.1-2020-10-01-full_build-www.gyan.dev Copyright (c) 2007-2020 the FFmpeg developers
  built with gcc 10.2.0 (Rev3, Built by MSYS2 project)
  configuration: --enable-gpl --enable-version3 --enable-static --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-lzma --enable-libsnappy --enable-zlib --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libdav1d --enable-libzvbi --enable-librav1e --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-libaom --enable-libopenjpeg --enable-libvpx --enable-libass --enable-frei0r --enable-libfreetype --enable-libfribidi --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libmfx --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
  libavutil      56. 51.100 / 56. 51.100
  libavcodec     58. 91.100 / 58. 91.100
  libavformat    58. 45.100 / 58. 45.100
  libavdevice    58. 10.100 / 58. 10.100
  libavfilter     7. 85.100 /  7. 85.100
  libswscale      5.  7.100 /  5.  7.100
  libswresample   3.  7.100 /  3.  7.100
  libpostproc    55.  7.100 / 55.  7.100
Input #0, mpeg, from 'ConCat2.vob':
  Duration: 01:26:30.42, start: 0.300300, bitrate: 5891 kb/s
    Stream #0:0(0x1bf): Data: dvd_nav_packet
    Stream #0:1(0x1e0): Video: mpeg2video (Main), yuv420p(tv, smpte170m, bottom first), 720x480 (SAR 8:9 DAR 4:3), 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc
    Side data:
      cpb: bitrate max/min/avg: 7500000/0/0 buffer size: 1835008 vbv_delay: N/A
    Stream #0:2(0x80): Audio: ac3, 48000 Hz, stereo, fltp, 192 kb/s

ffmpeg encoding result summary screen:

x265 (info): frame I:     74, Avg QP:19.75  kb/s: 15050.33
x265 (info): frame P:    902, Avg QP:21.58  kb/s: 12471.95
x265 (info): frame B:   2621, Avg QP:26.88  kb/s: 3518.91
x265 (info): Weighted P-Frames: Y:6.5% UV:5.9%
x265 (info): consecutive B-frames: 3.7% 2.2% 39.7% 30.9% 23.6%

encoded 3597 frames in 3196.04s (1.13 fps), 6001.25 kb/s, Avg QP:25.41
(aac @ 000001a27fe3ccc0) Qavg: 314.316

x265 (info): frame I:     74, Avg QP:19.78  kb/s: 15170.72
x265 (info): frame P:    890, Avg QP:21.60  kb/s: 12635.53
x265 (info): frame B:   2633, Avg QP:26.82  kb/s: 3698.17
x265 (info): Weighted P-Frames: Y:8.4% UV:7.6%
x265 (info): consecutive B-frames: 3.7% 2.4% 35.9% 33.0% 25.0%

encoded 3597 frames in 3196.02s (1.13 fps), 6145.55 kb/s, Avg QP:25.38
(aac @ 000001a200728f80) Qavg: 314.316

x265 (info): frame I:     74, Avg QP:20.40  kb/s: 14358.58
x265 (info): frame P:    813, Avg QP:22.09  kb/s: 12347.13
x265 (info): frame B:   2710, Avg QP:26.81  kb/s: 3986.21
x265 (info): Weighted P-Frames: Y:14.5% UV:13.0%
x265 (info): consecutive B-frames: 1.1% 1.9% 20.0% 44.3% 32.7%

encoded 3597 frames in 3196.01s (1.13 fps), 6089.35 kb/s, Avg QP:25.61
(aac @ 000001a20072b880) Qavg: 314.316

x265 (info): frame I:     74, Avg QP:19.78  kb/s: 15063.06
x265 (info): frame P:    903, Avg QP:21.57  kb/s: 12490.80
x265 (info): frame B:   2620, Avg QP:26.88  kb/s: 3506.11
x265 (info): Weighted P-Frames: Y:6.4% UV:5.6%
x265 (info): consecutive B-frames: 2.9% 2.6% 40.9% 30.8% 22.8%

encoded 3597 frames in 3196.01s (1.13 fps), 5999.41 kb/s, Avg QP:25.40
(aac @ 000001a2005343c0) Qavg: 314.316

x265 (info): frame I:     74, Avg QP:19.81  kb/s: 15185.65
x265 (info): frame P:    888, Avg QP:21.59  kb/s: 12655.86
x265 (info): frame B:   2635, Avg QP:26.82  kb/s: 3687.45
x265 (info): Weighted P-Frames: Y:8.8% UV:7.8%
x265 (info): consecutive B-frames: 2.7% 2.4% 37.5% 33.1% 24.3%

encoded 3597 frames in 3196.01s (1.13 fps), 6138.05 kb/s, Avg QP:25.39
(aac @ 000001a200537a80) Qavg: 314.316

x265 (info): frame I:     74, Avg QP:20.41  kb/s: 14386.07
x265 (info): frame P:    815, Avg QP:22.09  kb/s: 12322.46
x265 (info): frame B:   2708, Avg QP:26.80  kb/s: 3988.57
x265 (info): Weighted P-Frames: Y:14.7% UV:13.1%
x265 (info): consecutive B-frames: 0.9% 1.2% 20.8% 46.5% 30.6%

encoded 3597 frames in 3196.02s (1.13 fps), 6090.74 kb/s, Avg QP:25.60
(aac @ 000001a200538cc0) Qavg: 314.316

x265 (info): frame I:     74, Avg QP:17.78  kb/s: 17517.32
x265 (info): frame P:    903, Avg QP:19.57  kb/s: 15024.90
x265 (info): frame B:   2620, Avg QP:24.80  kb/s: 4860.86
x265 (info): Weighted P-Frames: Y:6.4% UV:5.6%
x265 (info): consecutive B-frames: 2.9% 2.6% 40.9% 30.8% 22.8%

encoded 3597 frames in 3196.02s (1.13 fps), 7672.84 kb/s, Avg QP:23.34
(aac @ 000001a2005363c0) Qavg: 314.316

x265 (info): frame I:     74, Avg QP:17.81  kb/s: 17620.88
x265 (info): frame P:    888, Avg QP:19.59  kb/s: 15156.42
x265 (info): frame B:   2635, Avg QP:24.74  kb/s: 5070.71
x265 (info): Weighted P-Frames: Y:8.8% UV:7.8%
x265 (info): consecutive B-frames: 2.7% 2.4% 37.5% 33.1% 24.3%

encoded 3597 frames in 3196.02s (1.13 fps), 7818.79 kb/s, Avg QP:23.33
(aac @ 000001a20053b5c0) Qavg: 314.316

x265 (info): frame I:     74, Avg QP:18.41  kb/s: 16755.65
x265 (info): frame P:    815, Avg QP:20.09  kb/s: 14822.84
x265 (info): frame B:   2708, Avg QP:24.71  kb/s: 5464.50
x265 (info): Weighted P-Frames: Y:14.7% UV:13.1%
x265 (info): consecutive B-frames: 0.9% 1.2% 20.8% 46.5% 30.6%

encoded 3597 frames in 3196.02s (1.13 fps), 7817.18 kb/s, Avg QP:23.53
(aac @ 000001a2006cb940) Qavg: 314.316