@Zaither-P Hi, I can't go into details but "The Ryzen 7 5800x does not have integrated graphics", so do you have a separate GPU?

Can you click your icon at the top of this page - My Profile & fill in your Signature with the full name of your CPU, GPU & amount of RAM, also inc the Windows & Vegas version, this will then show at the bottom of your comments,

done!

@Zaither-P As you can't reproduce this if that's what 'couldn't get a scenario where rendering would only use a single core' means it's going to be hard to work this out.

I have a similar PC - AMD CPU with no integrated graphics & an RTX GPU.

Some fxs are more CPU intensive than others, as I understand it older 'software' was CPU based, a while back they started making things more GPU or RAM orientated because they could be upgraded easier than CPU's. That's just a thought 🤷‍♂️

I use the options with (NVENC) because I have no integrated graphics & rarely look to see what the CPU is doing so sorry I can't help.

Can you list out the Fx in use? There must be a bottleneck somewhere.

Did this happen with older builds of 21 (pre 300)? The new video engine doesn't have everything working on the GPU yet, though why it would fall back to one core is another question. I haven't tested nested timelines though.

It is not necessary that this is a mistake. If the project (as a whole) is calculated on a video card, then the processor will be loaded - a couple of cores are larger, the rest are smaller. In this case, the graphics card loading schedule is also important.

After further testing, I have discovered that a nested project using PNG files preforms significantly worse than one using JPEG files. I imported a nested timeline that used several PNGs (with pan and crop going on) - when rendering, this caused Vegas to use a single core. The preview also took a significant performance hit. However, rendering inside of the nested project file performed normally. I've also tested with PNGs at different resolutions and pixel formats.

Bump

@Zaither-P There are dozens of render formats (codecs) in Vegas. Only a couple are optimized for multithreaded (GPU) rendering.

And that renderer must be chosen in your your Video and File I/O Properties.

And the vast majority of renderers are all conventional CPU single core codecs from yesteryear.

And the vast majority of effects in Vegas are legacy, meaning they still use a single thread for processing, and it only takes one to bottleneck the entire system.

And yet, you have told us nothing about your rendering properties and almost nothing about your project environment.

For intelligent answers to your question, and going forward, please make a note provide all of the render and environment details, as our crystal balls tend to cloud up and malfunction during these periods of solar activity.

https://www.vegascreativesoftware.info/us/forum/faq-how-to-post-mediainfo-and-vegas-pro-file-properties--104561/

@Zaither-P There are dozens of render formats (codecs) in Vegas. Only a couple are optimized for multithreaded (GPU) rendering.

And that renderer must be chosen in your your Video and File I/O Properties.

And the vast majority of renderers are all conventional CPU single core codecs from yesteryear.

And the vast majority of effects in Vegas are legacy, meaning they still use a single thread for processing, and it only takes one to bottleneck the entire system.

And yet, you have told us nothing about your rendering properties and almost nothing about your project environment.

For intelligent answers to your question, and going forward, please make a note provide all of the render and environment details, as our crystal balls tend to cloud up and malfunction during these periods of solar activity.

https://www.vegascreativesoftware.info/us/forum/faq-how-to-post-mediainfo-and-vegas-pro-file-properties--104561/

Render template: Default MAGIX AV1 1920x1080 59.940p 8 bit 4:2:0
everything else: https://www.mediafire.com/folder/55paeq0tafd2o/

I just finished a short video for a church. Sorry, I have to disagree about using a single core for rendering, even if it is to AV1. The video mostly consists of DJI Mini 3 Pro 4K Cinelike-D footage with Bit rate set to 100Mb/s.

First, I personally don't bother with AV1 since my hardware doesn't support it, but it will render using what I have.

Here is a screenshot while rendering, and showing the render settings. There has to be something wrong at your end.

And here is my usual MP4 AMD VCE. The rendering is just starting. The GPU will stay close to 100%.

The only thing I basically did was at titles, and use Boris FX Sapphire S_Aurora. I didn't nest anything. You say you used external OFX plugins, but fail to give any information as to which ones are used.

I just finished a short video for a church. Sorry, I have to disagree about using a single core for rendering, even if it is to AV1. The video mostly consists of DJI Mini 3 Pro 4K Cinelike-D footage with Bit rate set to 100Mb/s.

First, I personally don't bother with AV1 since my hardware doesn't support it, but it will render using what I have.

Here is a screenshot while rendering, and showing the render settings. There has to be something wrong at your end.

And here is my usual MP4 AMD VCE. The rendering is just starting. The GPU will stay close to 100%.

The only thing I basically did was at titles, and use Boris FX Sapphire S_Aurora. I didn't nest anything. You say you used external OFX plugins, but fail to give any information as to which ones are used.

As stated in my previous post, this issue happens when there is a PNG file within a nested project's timeline

Still not providing information asked for, why?

@Zaither-P I just did several AV1 renders, a UHD clip with a nested timeline that inc pngs (nested & with the nested dragged in), different aspects & frame rates, here's 5 of those

There must be more to your problem than 'PNG file within a nested project's timeline'

@Gid thank you for testing! I will see if I can narrow it down further.

If I use hardware encoding and then put mask and feather on the first section of project I get something similar to your CPU core use because Vegas feather is so bad (isn't it time for that to get upgraded?) It looks more like a plugin processing problem.

I tried software AV1 saw no problem with it

@Zaither-P Ok. I downloaded your project & I do see a single core being mainly used, how I rendered it anyway. I haven't broken it down or loooked into it deeper.

This is the project I downloaded from your web page, it wouldn't let me download multiple files which was a pain so @RogerS @Reyfox @gorGaram @mark-y If you want to try it I've put it on Google Drive, I haven't altered it in any way, folder on my desk is only 1.19mb https://drive.google.com/drive/folders/1JRWErs1ONOyWUeCDAgJCWVvKfbqhWU8B?usp=drive_link

I found it doesn't matter what size project, so just drag the .veg onto the timeline, Render as - Magix AV1 (change a template to match the project), I dragged the project to make it loop plays so it takes longer to render, it was going too fast to see what was happening in Taskmanager, mine doesn't show individual graphs, the darker the blue the more a thread is being used.

@UltraVista 

Your render dialogue just shows 'Rendering 3%', what render template did you use.?

Mine & the OP says 'Writing AV1 into file',

@Gid I reproduced this with your render settings.

@Gid I messed up, I encoded AV1 to project resolution 60fps, I didn't see the single core activity so I modified the project and then used hardware encoding. I tried just then with modified project encoding to AV1 1080P 60 but still getting 100% CPU utilisation. The screen cap shows modified project hardware encoding. @gorGaram has verified the problem

Okay, after doing a bunch more tests- it seems like nested timelines preform terribly in general. I did some super basic tests with many jpgs, few jpgs, many png, few png, motion, no motion. Despite all these tests running completely fine when opened in their respective projects, when importing them as nests, they all took significant performance hits and seemed to rely on a single core for rendering. here are my files for you guys to test with yourselves.
https://drive.google.com/drive/folders/1g7HqVtFHbyWi061YkpAmXZx0qtNPxb5H

still using MAGIX AV1 1920x1080 59.940p 8 bit 4:2:0 as my render template

Edit: just read what @Gid said - basically I've come to the same conclusion.