Decoding Motion JPEG results in poor contrast image

[RasterEyes]

Description of problem or question:

I have a new video capture card that outputs an absolute firehose of data, about half a GB per second with 4K video. The only option to tame this huge data rate is saving video using M-JPEG.

I can convert the gigantic raw video files to much more manageable MKV files, using H.265 video, without a problem. Until I install a new 4TB M.2 SSD, however, I can't record very much more than about 20 minutes of video. (Only on-board M.2 SSDs are fast enough to suck up this much data.)

The optional M-JPEG output files are much, much smaller, but still way bigger than you'd want to use as a final video product. They look fine played back before conversion to H.265, but suffer from too-bright black level after conversion to H.265, create a gauzy, low-contrast look.

Maybe there's just some flag the specifies the gamma or color range or the like that's getting lost or changed incorrectly?

Oddly I only notice this conversion problem when I play the video back using my Zidoo media player (which has no problem with the converted firehose data). Played back using VLC, the contrast still looks okay with the post-conversion result from the M-JPEG source.

Steps to reproduce the problem (If Applicable):

Start with an M-JPEG/AVI source, try to convert to H.265 (I doubt it would make much difference if H.264 or MP4 were the target format).

HandBrake version (e.g., 1.0.0):

1.8.2

Operating system and version (e.g., Ubuntu 16.04 LTS, macOS 10.13 High Sierra, Windows 10 Creators Update):

Windows 11 Enterprise, 23H2.

HandBrake Activity Log ***required*** (see How-to get an activity log)

https://pastebin.com/2CNqD3K9

[RasterEyes]

More log info:

https://pastebin.com/a8nEYKCL