This problem has driven me nearly crazy until I found the solution, and I’ll bet it’s done the same to many of you out there. You’ve just created a MP4 file with Sony Vegas, Premier Pro, or some other NLE, and it won’t play until the file downloads completely. Arggg! Why is it that other MP4 files will stream, and mine won’t?!?!
As it turns out, for some mind bending reason, a number of video editing apps do not output the correct Mp4 file header to allow the video to begin playing once the first few seconds have been buffered. I cannot fathom why this is. It’s certainly not the case with WMV (Windows Media) or MOV (Quicktime) files. In fact, Vegas has a checkbox for both file types that correctly encodes the file for streaming.
I finally ran across this great little app called “MP4 Faststart”, and it actually corrects the problem. It simply processes the file, and updates the header to allow a progressive download as the video plays. Amazingly, it’s free. Well actually, it’s donationware, and I think you’ll find it’s worthy of a few bucks to the developer, as it will save much head banging.