Investigate if theora and h264 compression in libav

[nilsbore]

The theora rgb image compression in ROS is not usable atm for unclear reasons, sometimes it works, sometimes it doesn't. But the FFV1 codec from libav works fine for the depth. So we should investigate if we can use the same image_transport code that we have already written but for the rgb image. Possible codecs could be theora or h264.