OK, I've done some testing on my i5-2500K / GTX 960 system.
I downclocked the 2500K to 3.1 GHz, as I believe that's the all-core frequency for an i5-2400.
There are two potential issues here:
1. The madVR config.
2. Media Center's hardware acceleration settings.
The default MC config seemed outdated as it's using D3D9 presentation, so what I first did was download the latest madVR and reset the config.
At 4.5 GHz, which I typically run my 2500K system at, nothing else was necessary for smooth playback of 24 FPS 4K HDR video.
At 3.1 GHz, CPU usage was a problem.
This is because Media Center defaults to DXVA2 (Copy-Back) for hardware decoding.
Copy-back is preferred as some features like Zoom Control are disabled without it, but if you have a slower CPU it may struggle at 4K.
The DXVA2 (Native) or D3D11 (Native) decoders were able to handle playback without dropping frames.
To change this, you need to either install the latest version of LAV Filters
or register MC's LAV Video decoder to the system.
For the latter:
- Open a command prompt with admin permissions.
- Run "cd %APPDATA%\J River\Media Center 24\Plugins\lav64\"
- Run "regsvr32 LAVVideo.ax"
This is my preferred method, as it means that it stays in sync with MC auto-updating LAV Filters.
For either option, you now need to tell MC to use LAV's Video Decoder:
- In Media Center: Tools > Options > Video > General Video Settings > Video Mode: Advanced - Custom
- Custom Video Mode Settings
- Start with the following settings: Red October HQ
- Now add LAV Video decoder.
- Open LAV Video Decoder's Properties and select the DXVA2 (Native) decoder.
Hopefully 4K HDR videos will play smoothly now.
With slower GPUs, there are options in madVR that will reduce the GPU load further, but the 1050 Ti should be faster than the 960 I was testing with.
And for what it's worth, it's reporting ~2.5/4.0 GB VRAM usage.