Desaturated colors after MeGUI conversion

[okoflaka]

Hi, I've got issue with color saturation after conversion.
It only applies (I hope) to 4K 10bits videos

I've noticed that AVS Script creator shows that source is:
LWLibavVideoSource("<file>", format="YUV420P8")
tried changing it to:
LWLibavVideoSource("<file>", format="YUV420P10")
but still on AVS preview and output file colors are dimmed.

Media info shows:
Chroma subsampling : 4:2:0 (Type 2)
Bit depth : 10 bits

I think this is the reason. On files with 4:2:0 (without Type 2) everything is ok (so maybe 8 bits vs. 10 bits is not the issue).

I've tried to convert with p8 - same effect.
I'm after 2 days of reading google, and only solutions are for SD sources (like here https://forum.videohelp.com/threads/353518-Slight-color-shift-with-x264)
and color matrixes, which does nothing for me.

One example. Dark areas are brighten, and red is just washed out

original (picture scale down for size reasons)

[Attachment 52356 - Click to enlarge]
And after conversion (same on AVS preview in MeGUI)

[Attachment 52357 - Click to enlarge]

Regards

P.S. I even tried viewing original file in MPC with limited range to 16-235 instead 0-255 and the image was sill more vibrant than after conversion.

[davexnet]

Is it converting HDR source to rec.709 color space without the tone mapping?

[okoflaka]

Essentially - not. My one goal is to reduce file size. No color/contrast/brightness conversion is intended. So I'm pushing down bitrate.

Original file

Video
ID                             : 1
Format                         : HEVC
Format/Info                    : High Efficiency Video Coding
Format profile                 : Main 10@L5.1@High
HDR format                     : SMPTE ST 2086, HDR10 compatible
Codec ID                       : V_MPEGH/ISO/HEVC
Duration                       : 2 h 20 min
Bit rate                       : 52.4 Mb/s
Width                          : 3 840 pixels
Height                         : 2 160 pixels
Display aspect ratio           : 16:9
Frame rate mode                : Constant
Frame rate                     : 23.976 (24000/1001) FPS
Color space                    : YUV
Chroma subsampling             : 4:2:0 (Type 2)
Bit depth                      : 10 bits
Bits/(Pixel*Frame)             : 0.264
Stream size                    : 51.3 GiB (91%)
Language                       : English
Default                        : Yes
Forced                         : No
Color range                    : Limited
Color primaries                : BT.2020
Transfer characteristics       : PQ
Matrix coefficients            : BT.2020 non-constant
Mastering display color primar : Display P3
Mastering display luminance    : min: 0.0050 cd/m2, max: 4000 cd/m2
Maximum Content Light Level    : 992 cd/m2
Maximum Frame-Average Light Le : 226 cd/m2

I'm converting with x264, no resize,

x264 command line:

--output-depth 10 (tried with and without it) --pass 2 --bitrate 10000 --stats ".stats" --deblock -3:-4 --b-adapt 2 --ref 5 --qpmin 10 --qpmax 51 --merange 20 --me umh --direct auto --subme 6 --partitions all --trellis 2

AVS script:

LoadPlugin("C:\Program Files (x86)\MeGUI\tools\lsmash\LSMASHSource.dll")
LoadPlugin("C:\Program Files (x86)\MeGUI\tools\avs\plugins\ConvertStacked.dll")
LWLibavVideoSource("D:\bb4k.mkv.lwi", format="YUV420P8")
#ConvertToYUV420P10()
#deinterlace
crop(0, 280, 0, -280)
#resize
#denoise

As you see AVS Script Creator from MeGui sets wrong colorspace format. Like I said before - changing it to YUV420P10 resulted in no change (same desaturated image)