I looked at it, and to me the filter looks like its not dependent on madVR, it was just made for madVR because at the time it was the only one to understand this kind of metadata - but since I defined that metadata more or less for LAV, of course JRVR understands the same.
Technically we allow adding extra filters into the DirectShow chain - if that works with live input however ... I don't have a setup to test.
For MC31.0.40 and up, I added the injector to our video post-processor filter whitelist, maybe we can get that working somehow.
I was able to get the metadata injector filter to affect the metadata when playing file-based media. But not from the capture card.
I registered the filter in Windows 10 and added the filter as a Video post processor filter in Custom JRVR mode. Screen shot attached.
I took a screen shot of the JRVR statistics when playing back an HDR video in Red October JRVR mode. (I didn't have an SDR media file to test with)
I then took a screen shot of the stats when playing the same HDR video in Custom JRVR mode with the filter.
The setting values I configured in the directshow_metadata_injector_filter.ini configuration file were applied overriding the original values for:
System (BT.709 instead of BT.2020)
Primaries (DCI-P3 instead of BT.2020)
Transfer (2.2 Gama instead of PQ HDR10)
Levels (Full/PC instead of Limited/TV)
I was never able to get the HDR10 Nits value to change. It would be reported as zero when I did not override the transfer from PQ.
Finally, I took a screen shot of the stats when playing an HDR video through the BlackMagic DeckLink 4K Mini Recorder capture card. No metadata values from the metadata injector filter were applied. So either there was no attempt to apply the filter to capture card input, or it failed.
Note that I will redo this test using an SDR file as a more realistic use of the filter.