I have a few MP4 files from youtube that I would like to join.

1. I tried virtualdub with avisynth (DirectShowSource). I am able to load up the video and I try to convert to xvid, but after a minute or so, it just stops encoding. Its not frozen because the timer is still counting, but it gets stuck on a frame.

2. I tried avidemux. When I convert to xvid I have the exact same problem, it freezes on a frame (not the same one)

3. I tried to just "copy" and it is able to successfully merge it, but when I play it back, many parts have the video frozen.

When I use avidemux and load the MP4 file, I get the "H.264 detect" asking me yes/no on if I want to switch modes. I say no because I don't want to lose frame accuracy.

Any tips on how I can merge these videos in a lossless fashion?

Thanks