From my observations, so4compoundplug decoder for HEVC(new) is only capable of using 2 cores of your CPU for playback and rendering. This is with GPU decoder set to on or off.

mxhevplug (legacy HEVC) will use all cores of CPU except when it only uses 2 cores for some files. A potential problem is that if it's like compoundplug (legacy AVC) it's not being updated so newer codecs that have been added only work with So4 decoder and only use 2 cores.

When I tested Legacy HEVCt previously I happened to be using files that only used 2 cpu cores for playback and performance was the same as SO4. Your research shows many HEVC files are capable of using all CPU cores when using Legacy HEVC.

Shouldn't they just kill S04 for HEVC? I don't see the point of it, causes too much confusion. The new decoder should not be infinitely worse at using modern CPU's

First playback is with SO4 decoder, 2nd is mxhev(Legacy) The cpu graphs speak for themselves.

@RogerS do you know the story of how Legacy HEVC became the default decoder, was it always that way or did they work out it was a dud after release?

@Former user, I often noticed you just changed the topic to talk/discuss e.g. when we concerned about the VEGAS opticalflow, you suddenly wished that I could try another software called so and so.

I didn't answer. It's not about politeness, it just had no correlation to my post, as now:

Purpose: fluent playback as much as possible by timeline cutting/arranging 

@RogerS, if I'm right, it's here about which codec will be used, not which hardware decoder.

if I'm right, it's here about which codec will be used, not which hardware decoder.

So why not test the AMD hardware decoder with non-legacy HEVC (so4compound) then? You have all the other options tested.

@RogerS, I think I got what you meant:

This was my primary setup - from my "logical thinking" - but it was the worst setup that I metioned at this post.

By the way, thanks to @Former user providing so many clips that I can use for the test.

Yes, that's right. I thought it would be helpful to describe the results of each option in one place (here).

If I am understanding this correction, it seems like HEVC + AMD decoding is bad, and the new decoder is worse than the legacy one. The best option was legacy HEVC on with AMD decoding off but it doesn't work with 10-bit. There is no good option for 10-bit HEVC.

Did I get that right?

As to Todd's question, I don't know the backstory with legacy HEVC being the default but perhaps the developers recognize the performance or compatibility of so4compound with HEVC isn't where they want it to be yet. The only decoder currently under development does seem to be so4compound.

@Former user, I often noticed you just changed the topic to talk/discuss e.g. when we concerned about the VEGAS opticalflow, you suddenly wished that I could try another software called so and so.

I didn't answer. It's not about politeness, it just had no correlation to my post, as now:

You didn't understand the Vegas optical flow for your selected scene looked terrible and nobody had the heart to tell you. The software I demonstrated is free, you could have tried it, and made a comparison but you some how felt offended on behalf of Vegas. The community is worse off because of it.

Legacy HEVC workS so much better than SO4 decoder, except that Legacy has no GPU decode which is really important for HEVC, and that's why it was introduced to Vegas. S04 AVC decode doesn't have the same 2 core processing limitation as HEVC, no idea why they can't fix that.

@Former user, I know that girl-clip with moving background is not suitable for slowmo. It was just a test about the ability of VEGAS' new function.

2ndly, I never install app that I don't use, not once for try or test whether it's free, good or bad.

I like one flow work environment, if I can't accomplish something in VEGAS, then I give it up.

As for the "investigation" here, I test and show result. I know less about the internal tech, thus say nothing about "because-therefore".

I hope my test can give a highlight to those who have similar hardware like mine.

I never felt offended, inversely, I fear I could offend someone. English is not my mother tongue.

If it were to you, take my apology please.