Thanks to Jonas Kulla <nyocurio@googlemail.com> for spotting it.
system timestamp and the first frame doesn't start from 0ms.
A frame consists of a list of rectangles, each of which represents the
-component-wise different between the previous frame and the current
+component-wise difference between the previous frame and the current
using a run-length encoding. The initial frame is decoded against a
previous frame of all 0x00000000 pixels. Each rectangle starts out
with