8k video on an iMac? I'm attempting to view 8k footage on my iMac however quicktime refuses to open it.

Footage is in H.264 AAC format at resolution 7680 × 4320, and when opened in quicktime results in audio but not video, just a black screen.

Converting the video with "MacX Video Converter Pro" to a lower resolution allows the video to be opened.

I am using the current iMac with a 5k screen and a R9 M395 graphics card.
It won't play lossless 8k video file, and you graphic card has nothing to do with that. However, i7 3***k generation processors desktop version will do the job.The video has to be loaded by your CPU to GPU and if your processor can't handle it, it won't play 24 fps+