Low CPU usage for rendering with new CPU

[integrityvideo]

I used to use a custom-built PC with a i7-9700k CPU and RTX Quadro 4000 graphics card for Premiere Pro / Media Encoder. When using CUDA acceleration, I would render out a 2-hr video mp4 3 Mbps 720p, it would use almost 100% of the GPU and 100% of the CPU, and would take about 8 minutes to render. 

I just built my own PC, and upgraded to an i9-12900k CPU, and kept the same GPU. My new system uses DDR5 RAM, instead of DDR4, and I now have nvme gen 4 disks instead of SATA, as bonuses. I was surprised to see that when I render the same video, it uses about 90% of my GPU, but only 25% of my new CPU, and the render time is still 8 minutes. Why isn't Premiere/Media Encoder taking full advantage of the more powerful CPU to cut down rendering time some more? Is this expected behavior? Thank you!

[integrityvideo]

I will add that the videos contain no video effects. I'm just stitching mp4 video files together and rendering out as mp4.

[mattchristensen]

@integrityvideo It sounds like maybe your new system is using Hardware Accelerated Encoding to take load off the CPU and use the dedicated encoding blocks on your chip instead. When you are on the export page, look at the summary on the bottom right and see if it says "Hardware Encoding" or "Software Encoding". You can also manually choose this in the video export settings. Try turning off Hardware Encoding and you should see full CPU usage. It may or may not be faster, it will depend on your system and your sequence.

[integrityvideo]

Yes, I am using Hardware Accelerated Encoding. I was before as well with the old CPU. My question is why with the old CPU, I was using almost 100% (with Hardware Acceleration turned on), but now it's only 25%. Thanks!

[MyerPj]

It's good you have a PP team member replying to you. I'll just say, it's easy to figure though. Your GPU must be the limiting factor. So, in the older system, your GPU was pumping out at about 100%, and to keep up, your CPU was at about 100%. Now you have the same GPU, but in order to keep up, your CPU only needs about 25% since it's much quicker. So, that's that. 

If your source footage is not 720p, then your GPU would be used in the translation of the framesize.

[integrityvideo]

That is helpful, thank you. It's odd to me that Premiere won't take full advantage of the CPU to encode faster, so that both GPU and CPU are utilized fully.

[R Neil Haugen]

That assumption is something most of us start with before we learn that the CPU and GPU are radically different devices.

They do not use the same code, nor even the same mathematical operations. They are not in any way, shape, or form interchangeable.

When a process can be done on either, there is a decision tree to decide which tool is used, and then that tool's specific code in the program is used. There are completely different code trees fir aby job depending on which tool is used.

Few things are split between them at the same time. Because it just doesn't work to do so.

In your case, that new CPU is strong enough to get ahead of what the rest of the system can do. So it idles some.

[MyerPj]

So that's really on us, to build a machine that is balance. Right now, your GPU is a weak link, I had that until a several months ago, when I built a 12th Gen in 2022, but used my existing GTX-1070, it worked fine, but was unbalanced with a new CPU and older GPU. Finally, I got an RTX-4070, and the hardware is balanced again.

Yours was a balanced machine, now it's not, like mine, favoring the GPU. So, when you are ready, thats the next upgrade, until now, it's going as fast as it can, and you'll see some improvement with a new GPU.

But inevitably, they are never as fast as 'they should be'. 🙂

[integrityvideo]

So I followed advice and upgraded to a 4070 Super video card. I was surpised to see that I'm still only using 25% of my CPU. More than that, I know that the 4070 Super is more than 2x faster than the RTX Quadro 4000 (similar in speed to a 2070). However, I only see a 25% performance increase in rendering (if that), and while my Quadro used 80 watts of power draw while rendering and 50% of GPU core load (90% of video engine load), my new 4070 Super only uses 50 watts of power draw while rendering and 33% of GPU core load. It seems to me this card has much more headroom for better performance, but I'm not getting it. Thoughts?

[integrityvideo]

(I'm using HWiNFO64) for these stats.)

[R Neil Haugen]

From having watched these discussions before, this sort of thing can then get down into BIOS settings for the card, and things like what "lanes" the card works on which are also used by what other resources. So at times, shifting which "lane" or "bus" something else uses frees up headroom for the GPU to increase speed.

Which is all to say that someone like @RjL190365 can give full advice, while I can speculate and list potential causes/solutions.

[MyerPj]

Yes, see my last sentence above. (ok, here it is)

"But inevitably, they are never as fast as 'they should be'." 🙂

That's kinda the nature of it. The software uses what it wants and that's it. You get a certain flow rate, imagine a 1/2" house hose you turn the spout all the way up and it comes out in a nice stream. Now you pump  that same amount of water thru a fire hose, and it will come out like a trickle. If you got a 20-25% increase in export time, I'll say that's pretty good. 

And remember: "But inevitably, they are never as fast as 'they should be'." 🙂

[integrityvideo]

Thanks. I've decided that a 20-25% increase in export speed for this level of video card is not worth $600, so I will return my system to what it was previously. If Premiere can find ways to take better advantage of the available power of video cards (utilize more available wattage/core load) in the future, I will reconsider this level of investment. 

[MyerPj]

Understood.

BTW: I went with the 4070 as I was using Topaz Video, and I was having some issues with it. So, I went for it (earlier this year) as I had been delaying due to the over inflated prices for the last few years. I got a big boost in Topaz with the 4070, and that's what makes it worthwhile, while also enjoying the benefits with PP.