Mediainfo, if you are not familiar, is a free app you can use to generate detailed reports on what kind of media you are dealing with, which is very helpful for us to help you diagnose the cause of your issue. Please download it, run it on your media, and show us the report it generates.

I tried both experimental and normal HEVC decoding but the problem stays the same. One screenshot is with the experimental HEVC decoder and one is without.

I've seen that before. VP21 can't play the video, you'll need an earlier vegas such as VP20. As far as I know no Vegas will be able to play the audio (Dolby Digital Plus). More annoyingly the reason VP21 can't play the video is because it does not respect your choice to use experimental decoder, it uses mxhevcplug always.

You'd need to transcode the video and audio, re-wrapping won't help.

@Former user What is this media? Did we test it before?

If not happy to test a sample if anyone can provide it.

@RogerS

It looks like I've misremembered, changing decoders with the mkv does not actually change decoders. Changing decoders with mov transcode does work, and you need to use experimental decoder, new decoder doesn't work.

I have this sample that won't play with the new decoder but the artifacting is different, It's not the same as OP's, but when compiling studio titles for a project a while ago I did see the same.

https://www.dropbox.com/scl/fi/dgcdp9gstahtvea7vqsey/Sample1.mkv?rlkey=71wlmct5vqs7cn8t69zsq7xet&dl=0

So rewrap with shutter Encoder while re-encoding audio, a negative is lower performance of experimental decoder combined with variable frame rate produced from the mkv to mov rewrap causing potental lag at edit points.

Thanks Todd. I tried rewrapping in ShutterEncoder to mp4 but it didn't decode properly with the non-experimental decoder as you wrote. Converting to AAC enabled the audio to work.

Mediainfo, if you are not familiar, is a free app you can use to generate detailed reports on what kind of media you are dealing with, which is very helpful for us to help you diagnose the cause of your issue. Please download it, run it on your media, and show us the report it generates.

Here would be the info of MediaInfo. A solution I have found is just converting it to h.264 with Adobe Media Encoder, but I am still curious on why HEVC doesn't work and nobody else seems to have the problem:

 

General
Unique ID                                : 215972697414758569472912596467735360115 (0xA27AD4195EBDB0A4E0C476F992A47273)
Complete name                            : C:\Users\richt\OneDrive\Dokumente\VEGAS\Projects\Death Edit\Puss.in.Boots.The.Last.Wish.2022.2160p.AMZN.WEB-DL.DDP5.1.HDR.H.265-FLUX.mkv
Format                                   : Matroska
Format version                           : Version 4
File size                                : 11.1 GiB
Duration                                 : 1 h 42 min
Overall bit rate                         : 15.5 Mb/s
Frame rate                               : 23.976 FPS
Writing application                      : mkvmerge v72.0.0 ('Minuano (Six-eight)') 64-bit
Writing library                          : libebml v1.4.4 + libmatroska v1.7.1

Video
ID                                       : 1
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main 10@L5@Main
HDR format                               : SMPTE ST 2094 App 4, Version 1, HDR10+ Profile B compatible
Codec ID                                 : V_MPEGH/ISO/HEVC
Duration                                 : 1 h 42 min
Bit rate                                 : 14.9 Mb/s
Width                                    : 3 840 pixels
Height                                   : 1 600 pixels
Display aspect ratio                     : 2.40:1
Frame rate mode                          : Constant
Frame rate                               : 23.976 (24000/1001) FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 10 bits
Bits/(Pixel*Frame)                       : 0.101
Stream size                              : 10.6 GiB (96%)
Language                                 : English (US)
Default                                  : Yes
Forced                                   : No
Color range                              : Limited
Color primaries                          : BT.2020
Transfer characteristics                 : PQ
Matrix coefficients                      : BT.2020 non-constant
Mastering display color primaries        : Display P3
Mastering display luminance              : min: 0.0001 cd/m2, max: 1000 cd/m2
Maximum Content Light Level              : 1013 cd/m2
Maximum Frame-Average Light Level        : 498 cd/m2

Audio
ID                                       : 2
Format                                   : E-AC-3
Format/Info                              : Enhanced AC-3
Commercial name                          : Dolby Digital Plus
Codec ID                                 : A_EAC3
Duration                                 : 1 h 42 min
Bit rate mode                            : Constant
Bit rate                                 : 640 kb/s
Channel(s)                               : 6 channels
Channel layout                           : L R C LFE Ls Rs
Sampling rate                            : 48.0 kHz
Frame rate                               : 31.250 FPS (1536 SPF)
Compression mode                         : Lossy
Stream size                              : 469 MiB (4%)
Language                                 : English (US)
Service kind                             : Complete Main
Default                                  : Yes
Forced                                   : No

Text #1
ID                                       : 3
Format                                   : UTF-8
Codec ID                                 : S_TEXT/UTF8
Codec ID/Info                            : UTF-8 Plain Text
Duration                                 : 1 h 41 min
Bit rate                                 : 57 b/s
Frame rate                               : 0.279 FPS
Count of elements                        : 1701
Stream size                              : 42.8 KiB (0%)
Language                                 : English (US)
Default                                  : No
Forced                                   : No

Text #2
ID                                       : 4
Format                                   : UTF-8
Codec ID                                 : S_TEXT/UTF8
Codec ID/Info                            : UTF-8 Plain Text
Duration                                 : 1 h 42 min
Bit rate                                 : 71 b/s
Frame rate                               : 0.343 FPS
Count of elements                        : 2102
Stream size                              : 53.8 KiB (0%)
Title                                    : SDH
Language                                 : English (US)
Default                                  : No
Forced                                   : No

Text #3
ID                                       : 5
Format                                   : UTF-8
Codec ID                                 : S_TEXT/UTF8
Codec ID/Info                            : UTF-8 Plain Text
Duration                                 : 1 h 40 min
Bit rate                                 : 58 b/s
Frame rate                               : 0.246 FPS
Count of elements                        : 1491
Stream size                              : 43.2 KiB (0%)
Title                                    : Canadian
Language                                 : French (CA)
Default                                  : No
Forced                                   : No

The answer is most likely

HDR format                               : SMPTE ST 2094 App 4, Version 1, HDR10+ Profile B compatible
Codec ID                                 : V_MPEGH/ISO/HEVC

isn't a variety of HEVC supported by VEGAS (yet). Can you find other ways of making these files (different HEVC or AVC type instead?)

The answer is most likely

HDR format                               : SMPTE ST 2094 App 4, Version 1, HDR10+ Profile B compatible
Codec ID                                 : V_MPEGH/ISO/HEVC

isn't a variety of HEVC supported by VEGAS (yet). Can you find other ways of making these files (different HEVC or AVC type instead?)

Yeah, I've been using Media Encoder to convert it to h.264 which works, but thanks for your help. Good to know for the future :D

Bit rate                                 : 14.9 Mb/s
 

That is an insanely low bitrate for 10 bit HDR media in an almost 4k resolution...

The properties reveal a Frankenfile, a combination salad of formats and metadata that has been patched together through multiple generations of encodes, and have not retained their integrity.

The properties simply do not go together.

That said, the file "may" play in some players, but is an unlikely candidate for nonlinear decoding to raw bits in Vegas, which is entirely different than normal playback.

My first choice to try for conversion to a recognized format is Shutter Encoder. You can also try Handbrake. Both are free.

The internet is literally full of this stuff. Hobbyists regularly re-encode material for social media without any regard for their original parameters, and "unbaking the cake" is often either a longshot, a kludge, or just not practical.

For fun, you could upload a sample of your "original" footage to Drive or Dropbox, and let us play with it in spare time.

The properties reveal a Frankenfile, a combination salad of formats and metadata that has been patched together through multiple generations of encodes, and have not retained their integrity.

The properties simply do not go together.

That said, the file "may" play in some players, but is an unlikely candidate for nonlinear decoding to raw bits in Vegas, which is entirely different than normal playback.

My first choice to try for conversion to a recognized format is Shutter Encoder. You can also try Handbrake. Both are free.

The internet is literally full of this stuff. Hobbyists regularly re-encode material for social media without any regard for their original parameters, and "unbaking the cake" is often either a longshot, a kludge, or just not practical.

For fun, you could upload a sample of your "original" footage to Drive or Dropbox, and let us play with it in spare time.

I guess it's a bluray rip so I won't be able to share it via Dropbox if I don't want to get in any trouble ;)
But, yeah, Media Encoder was the only program, which reliably converted it to a readable file. I tried VLC but that crashed all the time :/

Glad you found a solution. If you d/l ripped media from the web, you get what you get. OTOH, in the US you can rip one copy of a disc for your personal use without much hassle.