The reason of this issue is caused by media player 12 (in windows 7 professional) using mircsoft default codec which don't support mp4 decode. The ffdshow codec can not replace microsoft default codec in windows 7 (windows7 does not allow that in default). I find some third party tools can switch media player default codec to ffdshow but this is really inconvenience for our customer. Is there any way I can make a program to switch microsoft default codec to ffdshow codec? Like change some entries in windows registry?