There are let's see ... how many times the pixels to compute in 4k versus 1080? About 2 million versus 8.25 million?
I am assuming you're using some long-GOP format out of that camera ... and you're now requiring more than four times the work every frame for the CPU to do the required dance number: decompress one or more i-frames, store them to RAM; recall the data-set of changed pixels for the next frame, recall the appropriate one or two i-frames, compute the changed pixels, create that next frame of video, store images to RAM; recall next frame's dataset, rinse & repeat.
I do hope your proxies are "small" by pixel dimensions and not by file size alone ... as you really want to use the included Cineform presets for best playback, rather than any H.264 codec/format choice. The files sizes are bigger BUT that is why the playback is so much improved: every frame is a complete frame just lightly compressed. Which is a ton easier on your computer to work with.
Using a smaller frame-size than the original media is fine with proxies. And to be sure, you are toggling proxies on/off with the Toggle Proxies icon in the Program Monitor's control block, right?
Yes. The a6500 uses h.264 which I am not a fan of.
I use the ProRes Proxy 1024x540 and i can edit like a breeze with this. I have edited 4k in PrPro in the past and very recently. Im not stranger to this, but only within the last two weeks did Lumetri start giving me the red bar.
Weird, right? Huh.
Which really sucks. Because I went from taking 25-30 mins to export my clip to 4 hours now... which is not good for business.
Does this happen if you add Lumetri to a 4k Prores, DNxHR or Cineform? What do you have your render engine set for CUDA, OpenCL, Metal?
I have not. I took a clip from my last shoot and it is in AME right now transcoding to DNxHR.
I only have the options for OpenCL or Metal and when this is set to Metal my system completely comes to a halt
that did not work. Transcoded over to DNXHR and re applied the same Lumetri Effect and the render time doubled....
What did you end up doing? Let us know.