Hi Roger. Thanks for the guidance. Here's some info that I hope will be helpful:

The build is 208.

Here's the latest mediainfo report: (below that is some clip info)

OS Name    Microsoft Windows 11 Pro
Version    10.0.26100 Build 26100
Other OS Description     Not Available
OS Manufacturer    Microsoft Corporation
System Name    EDITOR
System Manufacturer    HP
System Model    HP Z2 Tower G9 Workstation Desktop PC
System Type    x64-based PC
System SKU    4Y0H8AV
Processor    13th Gen Intel(R) Core(TM) i9-13900K, 3000 Mhz, 24 Core(s), 32 Logical Processor(s)
BIOS Version/Date    HP U50 Ver. 03.02.03, 5/2/2024
SMBIOS Version    3.6
Embedded Controller Version    18.03
BIOS Mode    UEFI
BaseBoard Manufacturer    HP
BaseBoard Product    895C
BaseBoard Version    KBC Version 12.03.13
Platform Role    Workstation
Secure Boot State    On
PCR7 Configuration    Elevation Required to View
Windows Directory    C:\WINDOWS
System Directory    C:\WINDOWS\system32
Boot Device    \Device\HarddiskVolume1
Locale    United States
Hardware Abstraction Layer    Version = "10.0.26100.1"
User Name    Editor\marc
Time Zone    Pacific Daylight Time
Installed Physical Memory (RAM)    128 GB
Total Physical Memory    128 GB
Available Physical Memory    110 GB
Total Virtual Memory    136 GB
Available Virtual Memory    116 GB
Page File Space    8.00 GB
Page File    C:\pagefile.sys
Kernel DMA Protection    On
Virtualization-based security    Running
Virtualization-based security Required Security Properties    
Virtualization-based security Available Security Properties    Base Virtualization Support, Secure Boot, DMA Protection, UEFI Code Readonly, SMM Security Mitigations 1.0, Mode Based Execution Control, APIC Virtualization
Virtualization-based security Services Configured    Hypervisor enforced Code Integrity
Virtualization-based security Services Running    Hypervisor enforced Code Integrity, Hypervisor-Enforced Paging Translation
App Control for Business policy    Enforced
App Control for Business user mode policy    Off
Automatic Device Encryption Support    Elevation Required to View
A hypervisor has been detected. Features required for Hyper-V will not be displayed.    

HERE'S MEDIA INFO:

General
  Name: 511_0467.MXF
  Folder: D:\Chapman 04 05 2025
  Type: Sony XAVC Long MXF
  Size: 26.62 GB (27,259,750,448 bytes)
  Created: Sunday, April 6, 2025, 9:58:16 AM
  Modified: Saturday, April 5, 2025, 7:05:26 PM
  Accessed: Wednesday, April 9, 2025, 1:48:24 PM
  Attributes: Archive

Streams
  Video: 01:05:08.471, 59.940 fps progressive, 1920x1080x32, AVC50_1920_1080_H422P@L42
  Audio: 01:05:08.471, 48,000 Hz, 24 Bit, 4 Channels, Linear PCM

Other metadata
  Regions/markers: yes
  Command markers: no
  UMID: 060a2b340101010501010d43-13-000000-516562f5700706c508004602028b05e7
  Source UMID: 060a2b340101010501010d43-13-000000-526562f5700706c508004602028b05e7

Media manager
  Media tags: no

Plug-In
  Name: mxfxavc.dll
  Folder: C:\Program Files\VEGAS\VEGAS Pro 21.0\FileIO Plug-Ins\mxfxavc
  Format: Sony XAVC / XAVC S
  Version: Version 21.0 (Build 208)
  Company: MAGIX Computer Products Intl. Co.

Thanks for that. So the media is Sony XAVC in a MXF container. I have media like that but nothing long enough to show an issue.

Could you make a sample available for testing, either publicly or privately (feel free to message me)? I'd like to see if it's also an issue with 21.208 here and with 22. I have two NVIDIA systems to try it on (though MXF in 21 doesn't seem to use GPU decoding so GPU model may not matter).

Hi Roger. Thanks for your reply. How can I best send you an hour long video clip? That's when the sync problem usually occurs in VP22 with the audio and video gradually falling out of sync over the length of the clip. This typically occurs with clips that I have rendered. I want to emphasize that point. The problem shows up in rendered clips. When I play them back, they don't stay synced, even though the audio and video are in sync on the timeline.

About sending you a clip, I usually use hightail.com to send videos to my clients, but you'd have to download it.

Hi Marc, I understand about the issue being with the rendered file. I'm happy to use the hightail service to download it, feel free to message me directly.

Could you also post a screenshot of your project and render settings so I can match them exactly?

Hi Roger. On my desktop I have a screenshot of my project and render settings for you but I don't know how to send them to you.

Roger, I could send these PNG screenshots to you if I had an emai address to send them to.

@Marc-Gold try clicking his avatar and "write a message" ?

Hi. Thanks for your input. I tried copying & pasting, and also dragging the files from my desktop into the comment area associated with Roger's avatar, but none of the files pasted. I also wasn't able to copy just the text from the menus in VP22 that Roger wanted to see. No luck there either.

@Marc-Gold there is the "Upload file" button on the bar above the comment box. Did you try that?

Hi.

I looked everywhere but couldn't find the upload file button.

OK. I looked a bit more and found the upload button. I'm going to post those menus that Roger wanted to see.

Thanks.!!

Hi Roger. Here are the files you requested. Sorry for the delay.

Hi Roger. Please give me an email address so that I can send you a video and audio file via hightail.com

Thanks.

Hi Roger. Here are the files you requested. Sorry for the delay.

Thanks Marc. Can you press "customize template" and show me exactly what's inside it? You are rendering using Mainconcept?

Hello again, Roger. I am providing two screenshots from a recent dance video. The client returned this video to me with complaints about the audio/video sync. Screenshot 1 shows the original audio in the top track along with the rendered audio in the lower track taken from the beginning of the 1.5 hour program showing the audio in good sync when comparing the original audio to the rendered audio. The 2nd screenshot shows the original audio in the top track along with the rendered audio in the lower track taken from the near end of the same video showing the audio significantly out of sync. So, the problem persists even with the settings we discussed in previous conversations .

Roger, RE: the previous message - here are the render settings that I used.

Just as a test, go into file i/o settings, enable the experimental/legacy AVC codec, reboot VEGAS so that the setting takes effect, and re-render it. do you still see the issue?

Hi. Thanks for your input. Here's a screenshot of my settings showing that the legacy AVC codec is on.

Based on your reports I tested renders with MagixAVC/NVENC, MagixAVC/Mainconcept and Apple ProRes.

In my testing when I enabled legacy AVC decoding while still using NVDEC I got accurate alignment in 22 (I also got accurate alignment in VP 21.208 using QSV).

It appears to be an issue using MXCompound decoding.

Happy to look at your files if you can make them available (privately is fine).

Hi Roger. My apologies if sometimes I'm a little slow. Can you tell me which of my settings is wrong, and which ones I need to change? I do have legacy AVC decoding enabled, and I am using NVENC. I do see in the render settings options Magix AVC/AAC MP4 which is what I've been using to render, but I don't see MagixAVC/Mainconcept associated with the MP4 option? What am I missing?

If you press "customize template" you can see the other options under MagixAVC. If you are rendering to MagixAVC with NVENC and then VEGAS is loading this AVC media using so4compound (legacy AVC checked) the audio appears to be in sync here for the renders I've done. In fact there's no issue with the rendered file at all from what I can tell, only how VEGAS reads it.

What seems odd to me is that a client only looking at the finished file in a media player is saying it's not in sync. If this whole project was edited with "enable legacy AVC" checked it should remain in sync when rendered.

It's hard for me to say exactly without seeing your source file and render what is going on- can you double-check the timeline sync of the project in VEGAS?

Hi Roger.

My videos are frequently dance productions and the dance teacher notices immediately if the students movements are not following the beats of the music as practiced in rehearsals. I, myself, cannot tell if they are or they aren't, but the wave forms do tell the story.

Tell me what you mean by "can you double-check the timeline sync of the project."