After 23/11/2014 commit labeled "Fixes issues with JAWTRenderer on
Java 7 under OS X. Based on contributions by Ingo Bauersach" video
renderer on Mac OSX (Java 6) is broken.
After some debugging I found that the call of method paint(null) [line
91 of JAWTRendererVideoComponent class] is the responsible of this
In the attachments there is an example of the issue.
1) calling paint(null) video is shown as it was downscaled with large blocks
2) without calling paint(null) video is rendered ok.
Hope this could help you with the develop.