The Start-Of-Frame (SOF) signal, physically
transmitted over the AXI4-Stream
TUSER0 signal, marks the first pixel of a video frame.
The SOF pulse is one valid transaction wide, and must coincide with the first pixel of
the frame, as seen in the previous figure. The SOF
signal serves as a frame synchronization signal, which allows downstream cores to
reinitialize, and detect the first pixel of a frame. The SOF signal can be asserted an arbitrary number of AP_CLK cycles before the first pixel value is presented on DATA, as long as a VALID is
not asserted.