VideoStudio: When a project is rendered in VideoStudio 2023 the resulting file is choppy on playback

Symptoms

Observed Issue: When a VideoStudio 2023 project is rendered to video file, regardless of wich format and profile is used, the playback is choppy, as if it were rendered in very low frame rate. The issue remains the same whether TV standard used is NTSC or PAL. When the same project is re-created and rendered in VideoStudio 2022, there is no issue.

A number of users have confirmed the problem appeared only after updating the program with service pack 1, that brings the build version to 26.1.0.268

Steps to replicate:
1. Start a new project in VideoStudio and import some video clips
2. Add splits, transitions, overlays, and/or titles
3. Render the project in any of the available formats with FHD and 25fps, or 30fps

Actual result:
--playback of rendered file is very choppy

Expected result:
--quality should be similar to the source video files used

Cause

Product bug

Resolution

This was reported to the Engineering, and a hotfix was recently provided. Please follow the steps below.

1. Close VideoStudio 2023 if it’s still running.
2. Download this hotfix onto the desktop
3. Decompress the zip file.
4. Open File Explorer and navigate to “C:\Program Files\Corel\Corel VideoStudio 2023” (default installed folder) and locate the “ulmp4lib.dll” file.
5. Rename the “ulmp4lib.dll” file to a different filename, such as “ulmp4lib.dll__”.
6. Copy the “ulmp4lib.dll” from the desktop and paste it to “C:\Program Files\Corel\Corel VideoStudio 2023”, replacing the original ulmp4lib.dll file.
7. Re-launch VideoStudio 2023.

The choppy playback should now be fixed.