You have MP4 files with unwanted portions. You want to trim these portions.
- Download XMedia Recode.
- Install the application.
- Open a MP4 file.
- Under the Format tab set
Profile = Custom
Format = MP4
File Extension = mp4
- Click the Video tab and set Mode = Copy on the middle panel.
- Click the Audio tab and set Mode = Copy on the middle panel.
- Click the Filters/Preview tab and set Start Time and to (End Time).
- Click Add to queue button (with the + icon) on the tool bar.
- Click Encode on the tool bar.
If you want to split a MP4 file to multiple files by time then just repeat the procedure except that in the 7th step, you specify appropriate time range for each file, for example from 00:00:00:0000 to 00:09:00:0000 for the first file, then from 00:09:00:0000 to 00:18:00:0000 for the second file, then from 00:18:00:0000 to 00:27:00:0000 for the third file, etc.