I have some video stored on Google Cloud Storage in mp4, i need the extract a thumbnail from them.
I looked to a number of solutions, and looks like they don't work with App Engine.
for example: http://www.xuggle.com/xuggler/
Do you have library that i could use to do this on Google App Engine in Java?
I finally went with Google Compute Engine and ffmpeg, implementation is in progress...
OK, after some searching, I've found following: Video website on google application engine
Sounds like similar problem to yours. The only difference is that the other thread checks for python solution. However answers seem to be quite programming language independent, so I think it will be worth a read.
For the documentation/inspirational purposes, it might be worth to describe your solution in this thread once you go for it.
This question looks related to Is there a Java API for mp4 files?
Xuggler says their project is a mix of java and native code. Native code will not run on java app engine.
Search for
java mp4 video decoder
and look for a decoders that only use java code. Perhaps this one will work: http://jcodec.org/guide/movstitch.html.