VideoPad (often) won't vary speed on VidCoder File

[Dart77]

Hi - I could be classed as a "Beginner" editor. This is a question for editors who know VideoPad and VidCoder pretty well.

What does VideoPad need in the source file to be able to vary the speed ? I use VidCoder a lot to alter the aspect ratio or mirror a clip before editing/rendering in VP (both of which VP can't do). But VidCoder seems to do something to a file that prevents VP being able to vary the speed (increase/decrease or reverse the speed, ie, play it backwards). Many times, approximately 1 in 3 times, after putting a file through VidCoder first (I always output in mp4), VP will then not be able to do speed variations, whereas it always can on that same file if not put through VidCoder first.

What happens is that VP preview can only play it forward (normal) at 100%. Any other variation like reverse at 100% or any other speed variation and that particular clip or segment just will not start to process. It just sits there cycling with the green bar not starting, OR, it progresses extremely slowly - eg it might take 25minutes to process 1 second of the clip.

This problem comes up so often and is very frustrating. VidCoder is doing something to the file, but only about 1 in 4 or 1 in 3 files. But everything else will work fine, it's only the speed function.

in VC, I have tried selecting "Align A/V start" on or off, same with Chapter Markers. Sometimes I redo the file again in VidCoder and then speed CAN be varied in VP! It's a strange, intermmittent problem. VP must need some sort of marker or something in the file to be able to vary and /or reverse the speed.

Would it be anything to do with the encoder Codec settings in VC? I just use the one it sets itself, which is H.264. There are other ones there like H.265, 10 bit, 12bit, Mpeg-2, Mpeg-4 etc.

Thanks.