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Pre-render is handled by CPU

Forum|Forum|1 year ago
July 18, 2024
7 replies
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Hello Adobe Community,

I've noticed that when I pre-render my timeline for smooth playback in Adobe Premiere Pro, the process seems to heavily utilize my CPU while my GPU remains almost idle. My system specs are: Ryzen 7 1700 CPU, NVIDIA GeForce RTX 3060 (12GB) GPU, and 32GB of RAM. During pre-rendering, my CPU is fully loaded, but my GPU usage is minimal. This leads me to believe that pre-rendering is handled by the CPU rather than the GPU.

Additionally, I've ensured that the rendering mode in my project is set to use CUDA cores, so the problem isn't that the rendering is set to be handled entirely by the CPU.

Is there a way to configure Adobe Premiere Pro to utilize the GPU for pre-rendering tasks? This would presumably make the process faster and more efficient given the capabilities of my GPU. Any insights or suggestions on how to offload more of the rendering tasks to the GPU would be greatly appreciated.

Thank you in advance for your help!

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Correct answer mattchristensen

@firexrwt What I'm saying is that if one or both of the situations I mentioned are happening, then nothing is wrong and the system is working as intended. Not every situation for video editing can fully utilize the CPU and GPU at the same time.

If you want to try an experiment, you could cut a longer clip into your timeline that has no effects on it, and just add one Lumetri color to it, and change the colors a bit. Then render the previews for that clip. You should see some GPU usage, even when rendering to ProRes, because Lumetri color is a GPU-based effect and if it's the only effect on a clip we know it will use the GPU pipeline. Essentially the Lumetri color rendering will happen on the GPU and then the CPU will do the ProRes encoding. This is an example of a scenario where Premiere Pro should be able to utilize both.

If that works, it proves that back in your normal sequence, some effects you are using are CPU-only and thus forcing the whole render to fall back to render on the CPU. But if you need those effects, there's nothing you can do about that for now.

Ann Bens

Community Expert

Moved to Discussion.

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firexrwtAuthor

Participating Frequently

Oh, got it. Will try to check it. Thanks!

mattchristensen

Correct answer

Community Manager

@firexrwt What I'm saying is that if one or both of the situations I mentioned are happening, then nothing is wrong and the system is working as intended. Not every situation for video editing can fully utilize the CPU and GPU at the same time.

If you want to try an experiment, you could cut a longer clip into your timeline that has no effects on it, and just add one Lumetri color to it, and change the colors a bit. Then render the previews for that clip. You should see some GPU usage, even when rendering to ProRes, because Lumetri color is a GPU-based effect and if it's the only effect on a clip we know it will use the GPU pipeline. Essentially the Lumetri color rendering will happen on the GPU and then the CPU will do the ProRes encoding. This is an example of a scenario where Premiere Pro should be able to utilize both.

If that works, it proves that back in your normal sequence, some effects you are using are CPU-only and thus forcing the whole render to fall back to render on the CPU. But if you need those effects, there's nothing you can do about that for now.

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firexrwtAuthor

Participating Frequently

@mattchristensen understood, thanks, so I should try to change the codec to the one, that GPU can render? Which of these should I consider?

mattchristensen

Community Manager

@firexrwt Got it, thanks for that information. Two possible things may be forcing your render to be CPU only, or maybe both of them. First, if there's any CPU-only effect in your effect tree, Premiere Pro will fall back to only rendering with CPU. We're working on ways to improve that in the future, but the fundamental reason is that while GPUs are fast, if you have to stop and copy the video frame from main memory to GPU memory, then back to main memory for the CPU-based effect, you waste more time copying the frames around and so we keep it on the CPU only. It's possible something in your effects stack or AfterEffects stack is CPU-only and causing this.

Second, ProRes is a CPU-only codec (except for recent Apple silicon chips which have hardware encode/decode). That means when Premiere Pro (or any application) writes ProRes, it is happening on the CPU. When you are rendering preview files you are essentially exporting clips as ProRes.

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firexrwtAuthor

Participating Frequently

@mattchristensen Okay, so the Video Preview format is set to QuickTime, and the codec is ProRes 422 LT. The pre-rendering is applied to clips where I've used transitions created with adjustment layers using the Premiere Composer plugin (which I believe utilizes only native adjustment layers). Additionally, pre-rendering is also applied to After Effects compositions that I've replaced certain clips with.

mattchristensen

Community Manager

@firexrwt Where possible Premiere Pro will utilize both the CPU and GPU, but not all video tasks make sense for that. Sometimes you'll see mostly one or the other being used.

If you open up the Sequence settings, (Sequence > Sequence Settings) what is the Video Preview format and codec set to? Also, in the sections you are rendering, what effects are on the clips?

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