Hello Fabrice,
please excuse me for not specifying the exact settings.
First, drag and drop your video into the main WinX window.
In the next window that pops up, select Output Profiles -> General Profiles and select "MP4 Video". Click OK.
In the main window, uncheck the Hardware Encoder box and check the "Use High Quality Engine" box. This will convert slower, but the quality will be much better. (In the purchased version, this is much faster).
Press RUN and the movie will be created ready to run.
Another tip: If you finish a movie with an editing program, and you might get a file extension with .MP4 (capital letters), this is already an indication of a certain codec. A .MP4 will not(!) work in PB after uploading.
WinX will also convert the .MP4 file (or other file bindings) to an .mp4 (lower case) and it will be correct.
I hope everything works out well and I look forward to your feedback.
Many greetings
Christian :))