I was editing such videos in Nvidia RTX 4070 without any problems. Problem only occurs in RTX 5090.

@marcinzm Hardware decoder is a setting under options/preferences/ file io.

The NVIDIA drivers fully support decoding for such video files, the problem is VEGAS doesn't yet. If you look in Hub this on the list of things in progress.

The problem also exists with any 50XX NVIDIA GPU- I have a 5070.

Does Vegas Pro 23 render such files much longer without GPU decoding in that case?

Thank you @RogerS I confirm, that setting hardware decoding to NONE, solved the issue temperary. Output video renders fine. Now it is time to wait for hardware decoder for Nvidia RTX 50xx series support from Magix developers.

In order to render the file it has to read it. If you are still using the i9-7900X it can't decode the media either so it shouldn't be any slower.

In my case the 50XX is blocking my Intel iGPU from decoding it so it's way slower to decode and render. It doesn't really affect me as I don't commonly use this kind of media.

I changed my CPU to Intel Core 9 Ultra 285K.

Is it sentence correct: "If you are still using the i9-7900X it can't decode the media either so it shouldn't be any slower."?

Please update your signature then.

The sentence was correct regarding the 7900X however an Intel Core 9 Ultra 285K is able to decode 10-bit 422 media. Does changing the decoding to QSV in file io and video processing to the Intel iGPU in preferences/video make the video work? You'd have a tradeoff here with better decoding but much slower processing of Fx as the 5090 wouldn't be doing much.

Ok. But maybe you have meant such sentence: "If you are still using the i9-7900X it can't decode the media either so it SHOULD be slower, because it cannot decode it.". I am a little bit confused.

I updated my signature.

No, that's not what I meant. If your IGPU and GPU can't decode the media turning the GPU decoding off won't make it any slower. It will be slow as the CPU has to do all the work.