full download and progress download mp4 with JW player

I found some mp4 trans-code by some encoder (eg: handbrake with default profile) need full download before playing in JW Player while some mp4 can be played using the progressive download method

The below is the reason and the fix :

It has to do with the moov atom on an mp4 being placed at the tail end of the video rather than the head of the video. So once you ffmpeg the video into your require h264 specs, you need to run qt-faststart on the video which will relocate the moov atom to the beginning of the video and your problem is fixed. Very simple syntax:

qt-faststart sourceVideo.mp4 finalVideo.mp4

for those who don’t have qt-faststart already installed on their CentOS computer:

shell> svn checkout svn://svn.ffmpeg.org/ffmpeg/trunk ffmpeg
shell> cd ffmpeg/
shell> ./configure
shell> make
shell> make tools/qt-faststart
shell> sudo cp tools/qt-faststart /usr/local/bin/qt-faststart

source : http://www.bashbang.com/geek/progressive-download-mp4-with-jw-player/