Joining MP4 files from youtube

[eng3]

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

[yetanotherid]

There's limitations when merging video files such as resolution and type of audio/video, but assuming each video is a single video which was split into parts and you now want to join them back together again....
YAMB will remux/slit join various file types as MP4. MKVToolnix will do the same using an MKV output format. You'll find them both with Google easily enough.

If your MP4s play okay as they are you probably won't have a problem with your newly joined file, but if you do try using YAMB to extract the raw video and audio track from each MP4 and save them to your hard drive. You can then use either YAMB or MKVToolnix to open/append the raw tracks and resave them as a freshly muxed file. I prefer to use MKVToolnix and save files as MKVs mainly because it's much faster than YAMB and MP4.

For really problematic video try AnyVideoConverter. It's one of those free "anything in, anything out" type programs but it does what it does pretty well. It'll automatically join video as it converts (I think the resolution has to be the same) and it's got a setting to bump up the audio sync fussiness if necessary which works well if audio sync is a problem. It converts to quite a few different formats including huffyuv which is lossless (although produces large files). As I'm too emotionally dependant on my usual conversion programs to use anything else I do sometimes allow AnyVideoConverter to convert video to a format my regular programs can work with (i.e. lossless video and audio inside an AVI) and convert them from there. If you're not as emotionally unbalanced as me though you could probably just let AnyVideoConverter convert straight to the desired output format.

If AnyVideoConverter fails then Format Factory is a very similar free program and one of them usually works. Format Factory will ask about installing it's codecs into the system when you install it but tell it not to. Not unless you can't already play the files you have. Format Factory still uses it's own codecs/splitters but installing them as system codecs/splitters may interfere with other programs using the ones you already have installed.