Open MPEG Streamclip. Go to the File menu and select "Open." Navigate to the location of your MP4 file. You can also specify a URL, if the file is hosted on the Internet.
Go to the Edit menu; it will provide you with editorial choices for changing your video. If you would like to shorten the beginning of your video, drag the indicator in your time line to where you would like the video to begin. Go the the Edit menu and choose "Select In."
The dark gray line at the bottom of the screen is now indicating the new length of your video.
Drag the indicator to shorten your video. Similar to shortening the beginning of your video, if you would like to shorten the end of your video, drag the indicator to the point where you'd like the video to end on the right side of your time line. Go to the Edit menu and choose "Select Out." This is called the "Out-point."
Remove a section from the middle of the time line; set an In-Point at the beginning of the section you would like to remove. Set an Out-Point at the end of the section you would like to remove. Go to the Edit menu, select "Out-point."
Go the Edit menu again and select "Delete." That section will be removed from the time line.
Move a section of your video. If you wish to move a section of video and place it elsewhere in your time line, you can use a similar method to deleting video. Using the Edit menu, set an In-Point and an Out-Point. Go to the Edit menu and select "Cut." Scroll to the point in your time line where you want to re-position the selected video. Now go to the Edit menu again and select "Paste."
Save your project; go to the File menu and select "Save." Select MP4 as your output format. Everything between the In-Point and the Out-Point will be saved to your MP4 file