Edit MP4 Header Information In Its Binary

Now I don't know the mp4 header structure, but there is quite a big change the length is not in there. Often length is calculated from the combination of bit rate an number of bytes in the actual data.

Your question begs a counter question though :p

What are you trying to achieve by this? Even if the length is somewhere in the header, what do you think you accomplish by make it longer?

MerijnB -  I basically want to fool the browser into believing that video received from the server is of a longer duration. So if the actual duration is 10 seconds I want the browser to believe its of (say) 20 seconds. Its just an experiment I am trying out checking if it is doable or not. My ultimate goal is to have server send a short video of duration 10 seconds every 10 seconds. The first video will have a long duration so that the browser will assume its just the first video its playing. The reason I am trying to do this is because when I play different videos after every 10 seconds I am getting a small lag/delay between playing of two videos. I want to eliminate this delay.