MP4Box: How to extract a given part of a mp4 video

[semantics]

Hello,

I'm new to video editing and also to this forum, I hope I selected the proper sub-forum for my question.

I want to extract losslessly subfiles from my MP4 videos with MP4Box.

According to the MP4Box documentation, I could use either

• -splitx or
• -splitz

for this purpose, the only difference between these two switches seems to be how the end time's adustment is handled (-splitz adjusts the end time to be before the last random access point sample).

As a beginner, I don't know which switch is more suitable for me, -splitx or -splitz?

Any advice would be very much appreciated.

[sneaker]

-splitx will cut more close to the time specified but the last frames may (or may not) be broken. Commonly, this will only affect the last 1 - 3 frames, e.g. the last 100 milliseconds. -splitz should cut without broken frames but the specified time might be missed by a lot depending on the keyframe interval. Commonly 0.1 - 10 seconds.

I'd say most people don't care about possibility of a few broken frames unless maybe they want to re-append some of the cut peaces. They won't even notice. So most people would use -splitx. If you plan on re-encoding anyways it is recommended to edit in a lossless domain like AviSynth to avoid any such limitations.