Videos which is only played by particular app! Need help to save it!

There's a app(i can't disclose the app name) which plays video stored in memory card and videos have no extension, by viewing the file sizes im assuming that they are the videos + I also check changing the extension with mp4 flv 3gp etc but no success. I then decompiled the app and saw that app is using ffmpeg-jni to play the videos. Anybody can help me in this? and yeah all videos have IGN in their meta tag.

Thanks