Bug 422515

SUMMARY
Adding multiple video files, or cutting a single file and then trying to add more than one video effect to that piece, causes the preview to become distorted (like and old TV with UHF antenna) and the rendered file will produce a black screen for that section of the video. 

Additionally, trying to apply an effect such as White Balance to a files pieces, after it has been cut up, will produce the same problem/error. The workaround for this, is to apply the effect before clipping/editing the video file in the editor. This will prevent it from happening. 

I do not have a workaround for this when trying to apply White Balance, or any other effect to separate video files in the same project. 

The problem also exists when applying Brightness and Contrast, or Gamma, and <insert effect>. Essentially any two or more visual effects. 

STEPS TO REPRODUCE
1. Add video file to project.
2. Drag to tracks.
3. Clip file into two or more sections.
4. Apply effect to one section, then apply to the next section.
5. Render.

OBSERVED RESULT
Result = second section will be black screen.

EXPECTED RESULT
Visible picture start to finish.

2ND ALTERNATE SCENARIO SAME BUG

STEPS TO REPRODUCE
1. Add 2 video files to project.
2. Drag files to tracks.
3. Apply effect to one file. 
4. Apply to the next file.
5. Render.

OBSERVED RESULT
Result = second section will be black screen.

EXPECTED RESULT
Visible picture start to finish.

3RD ALTERNATE SCENARIO SAME BUG

STEPS TO REPRODUCE
1. Add video file to project.
2. Drag file to tracks.
3. Apply visual effect to file such as White Balance. 
4. Apply Brightness to same file.

OBSERVED RESULT
Preview screen becomes distorted and unable to play video properly. Render is corrupted.

EXPECTED RESULT
Visible picture in preview window with applied effects. Properly rendered file with both effects in place.



SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: Linux Mint 19.3 - Cinnamon 4.4.8 - Kernel 5.3.0-53-generic 
(available in About System)
KDE Plasma Version: 
KDE Frameworks Version: 19.12.3
Qt Version: 

ADDITIONAL INFORMATION

CPU - Intel© Core™ i3-6100 CPU @ 3.70GHz × 2
RAM - 31.3 GiB
GPU - NVIDIA Corporation GP106 [GeForce GTX 1060 3GB]