Voukoder is a third-party encoder addon, with no support from Vegas Creative Software or Magix.

That said, your encode setting of QP 15 is highly suspected, as the output file will be many X the source bitrate and file size. Try QP 27 with your Nvidia machine encoder and see how it goes.

I doubt QP 15 is the problem. Its just produce a bigger file, much higher bitrate what is needed.
Check your nvidia driver, opengl settings at nvidia control panel, dynamic ram size in vegas, etc.

Crash is always exactly at the same point in timeline?

Probably an issue with VEGAS at that point on the timeline than Voukoder.

I assume the Voukoder program and connector are current.

yes, current versions

Voukoder is a third-party encoder addon, with no support from Vegas Creative Software or Magix.

Yes it is, but so?

That said, your encode setting of QP 15 is highly suspected, as the output file will be many X the source bitrate and file size. Try QP 27 with your Nvidia machine encoder and see how it goes.

Highly suspect, many X the source bitrate? Honestly not sure what you mean by that.The source bitrate is an XAVCS 4k 10bit file with 140Mb/s. This Voukoder setting results in a render bitrate of around 7 mB/s, which is very low in my books, but that is the whole point of Voukoder. Higher quality with low file size. I usually export at 16mB/s for good quality with the other encoders. What is "needed" is very much dependent on the quality you want.

I doubt QP 15 is the problem. Its just produce a bigger file, much higher bitrate what is needed.
Check your nvidia driver, opengl settings at nvidia control panel, dynamic ram size in vegas, etc.

Crash is always exactly at the same point in timeline?

Voukoder is the only render engine that crashes. The Magix and Sony H264 AVC renders are just fine at any bitrate. My drivers are up to date, and I don't quite know what the Nvidia opengl settings have to do with the issue? I might try the old "dynamic RAM to zero" spiel before rendering, but I stopped needing to do that since V17.

I am using Voukoder (latest) here at 4K with following settings:
 

gpu=0 multipass=disabled preset=p7 profile=high qp=15 rc=constqp tune=hq

(GPU=0 is my nVidia 4090)

No issues with long renders, (videos are usually 1 hour plus) except a slow down during some text and transitions (x-fades) but this was also the case in V20.

As you've isolated it as a Voukoder issue I would report it there and they'll likely request logs to help troubleshoot what is going on. https://www.voukoder.org/forum/

In general you can select whatever bitrate you like.

Dynamic ram preview, etc. is usually to fix issues on the VEGAS end rather than the encoding end and if MagixAVC renders work then the VEGAS end is fine.

@Mindmatter There's no Voukoder H264 1080p template. Voukoder adepts the project resolution, seems to be 4k in your case. Downscaling 2160p to 1080p with Voukoder is only possible when setting first Vegas project resolution to 1080p before starting rendering with Voukoder.

Also I don't agree that a QP15 setting just produces a 7Mbps 1080p file, maybe that's the bitrate when you render a black background or a still image, but never when it's hires video with movement.

What makes you sure that's a Voukoder issue? Does Vegas hang or does Voukoder hang, what's the error message?

@Mindmatter There's no Voukoder H264 1080p template. Voukoder adepts the project resolution, seems to be 4k in your case. Downscaling 2160p to 1080p with Voukoder is only possible when setting first Vegas project resolution to 1080p before starting rendering with Voukoder.

Also I don't agree that a QP15 setting just produces a 7Mbps 1080p file, maybe that's the bitrate when you render a black background or a still image, but never when it's hires video with movement.

What makes you sure that's a Voukoder issue? Does Vegas hang or does Voukoder hang, what's the error message?

I simply set a scale ( Z-Lib) filter to reduce the 4k project to 1080 in Voukoder. That is my template / preset, including the other settings I chose. Reducing the 4k project settings to HD is not a good idea IMO.

Media info clrearly shows me 7mBs on the render.

As I already said, other render engines work just fine, only Voukoder crashes, the message is Vegas stopped working.

Did you post on the Voukoder forum? I doubt anyone here can help.

Yes, I see now that you are compacting your XAVC 4K to 1080p.

Still, QP 15 is overkill. Maybe the suggested HEVC starting point of QP 27 won't help you, but I'm puzzled why you're not using the kinder and gentler x264 AVC for HD encoding.

Did you post on the Voukoder forum? I doubt anyone here can help.

Not yet, I posted here first as I know there are people here using Voukoder.

Yes, there are many of us- I am a Voukoder / NVIDIA user. It doesn't seem to be a setting issue as this render is a very plain one through Voukoder (from your main tab- assume the only filter is zscale). I assume the studio driver is a recent one.

Here's how to find the log file: https://www.voukoder.org/forum/thread/614-where-do-i-find-the-log-file/

@Mindmatter Tried a render of a 4k project (an obs 4k avc remuxed screen-capture) with your settings on my laptop... no problem. Could be the Nvidia driver version if yours are too old. You can check the Voukoder site for the minimum Nvidia driver they require. I have Studio v537.58. It's more likely something in your project... suggest trying some Magix presets to see if they also fail. Here are the Voukoder settings I used trying to match yours... also, audio: aac; output: mp4:

@Mindmatter Tried a render of a 4k project (an obs 4k avc remuxed screen-capture) with your settings on my laptop... no problem. Could be the Nvidia driver version if yours are too old. You can check the Voukoder site for the minimum Nvidia driver they require. I have Studio v537.58. It's more likely something in your project... suggest trying some Magix presets to see if they also fail. Here are the Voukoder settings I used trying to match yours... also, audio: aac; output: mp4:

 

Thanks, I did end up using the Magix AVC export, which works just fine. I'm on Nvidia 537,58 too.

@Mindmatter There's no Voukoder H264 1080p template. Voukoder adepts the project resolution, seems to be 4k in your case. Downscaling 2160p to 1080p with Voukoder is only possible when setting first Vegas project resolution to 1080p before starting rendering with Voukoder.

Also I don't agree that a QP15 setting just produces a 7Mbps 1080p file, maybe that's the bitrate when you render a black background or a still image, but never when it's hires video with movement.

What makes you sure that's a Voukoder issue? Does Vegas hang or does Voukoder hang, what's the error message?

I simply set a scale ( Z-Lib) filter to reduce the 4k project to 1080 in Voukoder. That is my template / preset, including the other settings I chose. Reducing the 4k project settings to HD is not a good idea IMO.

Media info clrearly shows me 7mBs on the render.

As I already said, other render engines work just fine, only Voukoder crashes, the message is Vegas stopped working.

A small render test with a 2160p50 clip (originally 100Mbps) on a 2160p50 timeline with Voukoder downscale (Z-lib) and QP15 rendered with an average of 30fps renderspeed, resulted in a 1080p50 with an average bitrate of almost 90Mbps. (remember the original 2160p50 clip is 100Mbps)

The same render test with a 2160p50 clip on a 1080p50 timeline with Voukoder and QP27 rendered with an average of 80fps renderspeed (almost 3 times faster), resulted in a 1080p50 file with an average bitrate of 15 Mbps!

I couldn't see a quality difference between both renders...only a huge difference in renderspeed and resulting file size!!!

@Mindmatter said: " ... other render engines work just fine, only Voukoder crashes, the message is Vegas stopped working."

 Have you looked in the Windows Event Log and/or Windows Reliability History for some clue for why Vegas Stopped working?