Thanks John.

My backup partition is on the same SSD. It''s a smaller partition with a few audio apps missing.

I never had an issue with XAVC-s, not even with So4.dll. I've no idea what's suddenly wrong with Vegas on this partition, especially that I haven't touched it since my last project, all I did was installing V16 and updating that. Graphics driver is exactly the same, as is the version of V15. It's this kind of issues that really can get me frustrated over hours of troubleshooting Vegas, not even knowing where to start.

EDIT: On V14, I get 25p at full / best!

With the exact same internal settings as V15 and V16...Go figure this one out.

Click on Resource Monitor / Disk. I'm curious to know if some process is hogging I/O and causing the Response Time (ms) of your source media to be higher than normal. The 2-3 ms that I measured was on my spinning Archive disk. Normally, I do projects on an NVMe disk and the response times are consistently low.

You've observed that the Preview performance is better when read from a different disk (partition).

John, that still does not explain why v14 gives me full 25p at full/best on the problematic partition. Something must have messed with v15 and 16 but what and why?

That’s a developer question.

This is a real showstopper. V15 and 16 have all of a sudden become unuseable. Any hint or solution is highly appreciated! Just updated the graphics driver, no change.

This is a real showstopper. V15 and 16 have all of a sudden become unuseable. Any hint or solution is highly appreciated! Just updated the graphics driver, no change.

Just curious. Did by any chance your default project settings change to 32bit?

OldSmoke, just checked, no still on 8 bit.

It's probably not something in this list, but it might be.

Thanks Nick,

but all these tweaks are already in place, except that I usually don't need any proxies with a simple XAVCs clip without any FX. This whole thing is just baffling.

With me XAVC-S video with 35 Mbps untill 55 MBps bitrate plays smooth in VPro 14,15 and 16 on Preview Best/Full.

Here an example of 55 Mbps XAVC-S playing in 14,15 and 16, without stutters or preview changes. To me looks, because it plays well on your VPro 14, that maybe you use other settings in VPro 15 and 16, because I show you this is not different in those Vegas versions.

No, as I said, the exact same settings, and my other partition, V15 /16 play the files correctly.

My last big XAVCs project was on this partition a few weeks ago and worked just fine. Haven't changed a thing in Vegas since, and now it's suddenly having the issue.

That you did not tell us or I missed that. The goal of working on more than one partition I can't copy because I don't see any goal, but maybe you have one.

j-v, I don't work on 2 partitions, it's just a safety / backup partition in case the main Win10 fails.

OK it' solved...by accident. here's how:

I ended up doing the project on V14 as it was the one that worked. The render, however, never had any sound, so I googled that issue. Someone suggested the solution is a preference reset and cache deletion ( hold shift + ctrl while starting Vegas ). I did that...and V14 still renders without sound, BUT...now V15 works! ( note that I did the reset on V14), not V15 ) Go figure...

Next thing was trying it on V16, which still had the issue, so I did the same with V16, which now...works too.

Still baffled but happy I can now get on with my work.

Maybe your disk partition with the slow read is being compressed. Some of the new Microsoft updates I received today had something added to temporary compress your disk in order to have (temporary) more diskspace for upgrading to new windows updates. As is the fall edition is eminent it may just be that.

..... a preference reset and cache deletion ( hold shift + ctrl while starting Vegas )....................Next thing was trying it on V16, which still had the issue, so I did the same with V16, which now...works too.

👍

Deleting the cached files in C:\Users\username\AppData\Local\VEGAS Pro\..... is always the first thing I do when something goes not as I expect it should. Doesn't harm anything, only the next start takes a little longer.
Maybe Nick Hope can list this in his FAQ?

It's already in the stability FAQ (#17). I'll add it towards the end of the smooth playback FAQ too. Unfortunately it's unclear whether the solution to Mindmatter's issue was a reset preference or the clearing of the cache.