I downloaded a movie in 2 parts each being about 250 mbs each. The movie(American Gangster) is cut in half into the 2 parts.
How do I join the two Mp4s together into one longer full movie? (Yahoo Answer)
MPEG Joiner Mac is a wonderful and easy-to-use joiner for MPEG files (MPEG-1, MPEG-2 and MPEG-4, etc.). Mac MPEG Joiner can join/merge all kinds of separate/individual MPEG files into one large file without any quality loss. Then you can keep the coherence of watching complete MPEG movie on Mac.

How to join/merge MPEG files together for Mac OS?
1. Free Download Mac MPEG Joiner and run it.
2. Import MPEG files with MPEG Joiner Mac.
Click "ADD files", you can load individual MPEG files to Mac MPEG Joiner.
3. Join MPEG files together Mac.
In the main interface, click "Merge into one file" to join/merge separate/individual MPEG files into one movie.
4. Start to join MPEG files Mac
Click "Start" button to join/merge MPEG files into one large file.
You also can get:
Video Editor Mac
AVI Joiner Mac
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WMV Merger Mac
WMV Cropper for Mac
MP4 Cropper for Mac
MP4 Joiner Mac
MKV Cutter Mac
MKV Merger Mac
FLV Splitter Mac
DVD Cropper for Mac