Low CPU Usage when exporting in certain scenarios

[Zach Gold]

Hey Everyone!

I'm new to the forum stuff lol, guess I'm lucky to have been editing this long without running into a head scratcher. I'm currently using an iMac Pro, with the 10 core xeon, 128 gb of ram, and vega 56 with 8 gb of vram. I'm currently on the current version of Premiere Pro. The machine is great, but I've been noticing some interesting trends with cpu usage that I'm wondering if anyone has an answer to. 

I edit in premiere, but I'm also a davinci resolve certified colorist, so I always cut in premiere and bring my timeline into resolve for grading, finishing, and the final export. I rarely export out of premiere unless it's a smaller project. I'll lay the scenarios out below, I did some different tests with various codecs, and then replicated those scenarios in resolve.

(Premiere Pro)

Exporting 6k R3D files into a single 4k prores 422 LT file: between 20%-28% cpu usage

Exporting 6k Prores files in a single 4k prores 422 LT file: between 20%-28% cpu usage

Exporting 6k R3D files into a single 4k h.264 file: between 85%-95% cpu usage

Exporting 6k Prores files into a single 4k h.264 file: between 85%-95% cpu usage

Exporting 6k R3D files into a single 4k h.265 file: between 85%-95% cpu usage

Exporting 6k Prores files into a single 4k h.265 file: between 85%-95% cpu usage

(Davinci Resolve)

Exporting 6k R3D files into a single 4k prores 422 LT file: between between 75%-90% cpu usage

Exporting 6k Prores files in a single 4k prores 422 LT file: between between 75%-90% cpu usage

Exporting 6k R3D files into a single 4k h.264 file: between between 75%-90% cpu usage

Exporting 6k Prores files into a single 4k h.264 file: between between 75%-90% cpu usage

Exporting 6k R3D files into a single 4k h.265 file: between between 75%-90% cpu usage

Exporting 6k Prores files into a single 4k h.265 file: between between 75%-90% cpu usage

Certainly something effecting cpu usage in premiere when it comes to prores exports. Mostly just curious if anyone has an idea why or if there's anyone with similar issues. Any ways to get my cpu usage higher would be would be nice well!

[R Neil Haugen]

@Bruce Bullis or @Fergus Hammond  ... do either of you have comments to enlighten us with?

Neil

[Bruce Bullis]

Sorry, I'm far removed from the details of format-specific render performance.

"Whereof one cannot speak, thereof one must be silent."

  —Wittgenstein


Speaking very generally, not all processes are CPU-bound; in some common scenarios, reading from or writing to storage could take up more of the export time than actual video processing. 

[Zach Gold]

I had actually checked that before I posted here. I moved my files I was testing with to my internal SSD on the imac pro, same result as my external raid. I didn't think it would be the issue due to the fact that the same process done in resolve used the extra cpu, and with it being resolve, lots of gpu, and as you'd expect ended up being much faster. I'm  pretty sure at this point it's a premiere issue.

[MyerPj]

What about the time element. Did you get the length of time for each export. If they all export at say 1 minute or 10 minutes then you are good. The software could be using all it needs? 

[Zach Gold]

When exporting to prores in premiere, it was taking a little over an hour. When exporting to a more compressed codec like h.264 or h.265, it was taking around 20 minutes. The CPU usage, or lack there of, seems to be effecting the time it takes to export certain codecs. As for resolve, the times were closer across the board, and across the board was using similar cpu usage 

[Phillip Harvey]

I don't know if you can monitor per core CPU usage on a Mac - maybe with a third party utility? - but I wonder if something about what you're doing in singe-threaded in Premiere, so overall/average CPU usage would be low, but you have one thread at 100% that's doing all the work. There are a few effects that traditionally have this kind of constraint (Warp Stabilizer comes to mind).  

But honestly, since your tests appear to be going from ProRes to ProRes that would really surprise me. Are you using the Max Render Quality checkbox when exporting? 

[Zach Gold]

I'd be curious about checking the usage of each core if possible, but like you said I doubt that's the issue, especially because at that point using 20% of 10 cores wouldnt make sense for just a single core to being used. I tried it with both max render quality checked on and off, didn't change the usage or time.

[MyerPj]

The h.264 has some GPU optimizations and in Premiere. The file sizes come into play somewhat.

[Zach Gold]

Yeah I noticed that. Exporting to h.264 utilized a lot of my cpu and I did notice my gpu putting in a bit of work. Exporting to prores didn't really use much of either which is the big head scratcher.