In Vegas Pro 20 Build 139 (not pirated) on Windows 10, I'm exporting a video saved in the Magix; Mainconcept AVC MP4 format, and unfortunately, the resulting video appears (generally) darker (some bits lighter) when I play it back in Media Player Classic, Chrome or Firefox/Waterfox.
However, it appears fine in the Vegas preview window, and also when I import the saved problematic video back into Vegas, it (again) appears fine in the preview window, perfectly matching the PNG original colours. Moreover, from the codec settings window, if I use the default "Intel QSV" encode mode instead of Mainconcept, then that also perfectly matches the original PNG colours, even in Media Player Classic, Chrome and Firefox/Waterfox.
Here's the original image:
Here's what the video image looks like when saved out using the Magix; Mainconcept AVC and then shown in Media Player or Chrome etc.:
You can swap between these in your browser (click the image and then "open image in new tab"), and you'll see the differences instantly.
The bug is easily reproducible by the way - in Vegas, open just a single image to make a video (the "Original image" above) lasting say, a few seconds, and setting the options as shown in the Magix; Mainconcept AVC codec (350x284 resolution).
What I've tried so far to solve the colour problem:
I tried importing a BMP and JPG (instead of PNG) of the same image, and tried a bunch of different settings in the MainConcept window (e.g: Project->Color space and setting Color range to "Full"). Again no joy.
Also tried to mess around with "Color space" and "Color range" in the media settings to no avail:
Project settings just look like this. Tried a few things there, but made no difference:
Codec settings can be almost anything, and the problem occurs, but here's what I have: