As the latency target alone is not ensuring that we start with a sane phase
shift between vsync and drawing, we read back the phase shift provided by the
mmal rendering statistics and use it to compute a phase offset which we apply
to the picture date, so that the core shifts the display call accordingly.
Doing this frequently allows us to resync if a distortion or display reset
caused the offset to break.
This is only enabled if mmal-adjust-refreshrate is enabled, because the whole
vsync synchronisation makes only sense if display and videorate match.
Signed-off-by: Julian Scheel <julian@jusst.de>
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>