@lenard “If you put your cursor on a 4K60HEVC time line on vegas, let it cache and play , no edits, Vegas will probably play it smoothly, But that's not what editing is, Vegas's HW decoder is terrible (for LGOP)

If you set the default of 200, which I and probably most people do, the cache gets used up in a few seconds. When I tested the OP's 26s clip, thats what happens, but if your being honest with your test, you ignore that and then observe say the last 20s+ to see what the real playback rate is.

Using test clips is still a valid test. No one is going to start passing around full projects for people to compare. The benchmarking project is there for that.

What are your machines specs, it’s useful to have them in your profile, then when you make broad statements about say poor playback (see above) for LGOP users can infer whether its really true or that you need a PC upgrade.

Naturally, I was curious about this, specifically playback of IPB vs ALL-I using hevc . At the moment VP16 is the only VP game in town to load and play this combination of media. I would hope that the next build will improve things.

Two 25s, 25 fps test clips, clog, 4K UHD IPB and ALL-I ... Standard, not "fine" quality.

IPB ..... Size 488 MB   Data rate ... 163,867 kbps
ALL-I ... Size 1.3 GB   Data rate ... 434,472 kbps

AVsupports 26s, 50 FPS clip ...

IPB ..... Size 352 MB   Data rate ... 98,758 kbps

#1 No Proxy's used
#2 Playback set to Full/Best 
#3 In preview window "Adjust size and Quality for Optimal Playback is un-checked"

#4 Forgot to mention, but also set DRAM from 200 to 0, the "real" FPS value settles down quicker.

I have used #1 to #4 with all of my previous playback tests, of course.

Playback FPS values measured near end of clip, not at start.

Laptop

IPB   ~ 0.8 FPS 
ALL-I ~ 0.8 FPS

PC

IPB   ~ 1.3 FPS
ALL-I ~ 15 FPS

AVsupports 26s clip follows ...

IPB ~ 2.5 FPS must be warmer here in Dublin today, previous was <2fps.

The following is simply the GOP structures of my two clips, Mediainfo doesn't display the LGOP ones. Mediainfo doesn't supply the AVsupport GOP structure, nor my util. It is understood to be LGOP. Update: I think though that the Sony clip has a GOP of 48 ... IBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBI

------------------------------------------- Start Date and Time .... 19/03/2021 .. 14:01:56.71 .........................
------------------------------------------------------------------------------------------------------------------------
[Q]
File ..... [ R5__0318-IPB-HEVC 10 bit 422.MP4 ]

GOP length=12,  M=3, N=12, Mini-GOP=IBBP ... GOP=IBBPBBPBBPBBI 
------------------------------------------------------------------------------------------------------------------------
[Q]
File ..... [ R5__0319-ALL-I-HEVC 10 bit 422.MP4 ]

ALL-I ... [ 1 ] 
II
--------------------------------------------- End Date and Time .... 19/03/2021 .. 14:05:12.26 .... Duration 00:03:15.49

Just worth adding in here again the results from the OP's 26s clip. Using VP16 with the #1 to #4 conditions met, today I get ~ 2.5 FPS, settles from around middle to end. Previous result was a bit less. I'll add it in above by way of comparison, the file size, data rate and clips frame rate are different of course, its from Sony, my test sample clips are from Canon.
 

One last thing Lenard RE: "maybe with your own screen recording showing HW 4K decoding of HEVC working better" I'm sure you're saying this in a generalised way, not me specifically, and as far as checking the credibility of my tests I don't feel a need to do this. If that is the case though you would be adding to an existing club of one. So that would be two.

for your entertainment, here's an advertorial highlighting nvidia vs M1 editing speed:

@lenard “If you put your cursor on a 4K60HEVC time line on vegas, let it cache and play , no edits, Vegas will probably play it smoothly, But that's not what editing is, Vegas's HW decoder is terrible (for LGOP)

If you set the default of 200, which I and probably most people do, the cache gets used up in a few seconds. When I tested the OP's 26s clip, thats what happens

What are your machines specs, it’s useful to have them in your profile, then when you make broad statements about say poor playback (see above) for LGOP users can infer whether its really true or that you need a PC upgrade.

It's a common fault, it's the same fault in VP15,16,17,18. To decode a 4K60 HEVC on a Pascal GPU NVDEC decoders run at 35%, when NVDEC goes to 100% frames drop and often will not recover. It's throwing hundreds of frames away and not rendering them although Vegas was only using 35% CPU. When you see lagging unrelated to CPU or GPU, always check hardware decoder. This is also an AVC problem

This fault is often seen at edit points where the user complains Vegas is dropping frames, if they were to check their GPU decoder window they would see the symptom of the fault but not the actual fault. The fault is with the software

 

One last thing Lenard RE: "maybe with your own screen recording showing HW 4K decoding of HEVC working better" I'm sure you're saying this in a generalised way, not me specifically, and as far as checking the credibility of my tests I don't feel a need to do this. If that is the case though you would be adding to an existing club of one. So that would be two.

It's why I always screen record including task manager showing ram,cpu,gpu,gpu decoder, cuda . Someone may notice something interesting I never did, then there's the various vegas settings as well. I was more interested in 4KHEVC60 playback with gpu decoding enabled, so 8bit 420, if problem free, but as users on vp17,18 can't see how 422 HEVC plays back, that is interesting also, although not being useable without hardware decode came as no surprise

Poor codec support may lead to something like that result:

please remember Vegas used to be a Sony program for a Sony user base

All of the Iphone12 users left. VegasDerek said he didn't consider that fix was important enough for last week's update, so 6months since the phone was released. And we also know the backwards compatibility HDR mode would work with dolbyvision if they stopped blocking 10bit HEVC, which would fix one of your major complaints also

I never said that a fix was not important enough for the update.

What ever will a pro NLE do without the millions of professional videographers out there who need professional level editing software to edit video they shot with a... phone. God help us that the team didn't prioritize that over supporting industry standard professional intermediate codecs or making the software run more stable than ever...

All of the Iphone12 users left. VegasDerek said he didn't consider that fix was important enough for last week's update, so 6months since the phone was released. And we also know the backwards compatibility HDR mode would work with dolbyvision if they stopped blocking 10bit HEVC, which would fix one of your major complaints also

@lenard Out of curiosity I just went looking for iPhone12 samples and all the ones I could find were 10-bit Hevc 420 DolbyVision encoded with backwards HLG HDR compatibility... which Vegas 18 had no problem with. Found a bunch of downloadable iPhone12 sample clips on Reddit here.