By manipulating the read back parameters Block Length (BL) and Line count Field (LCF) information provided by STDI we can work out the vertical refresh rate as follows:
(Block Length x XTAL Period)/8 = T line of video
T line of video x LCF = T frame of video.
(1 / T frame of video) = Refresh rate.
E.g for 720p60 BL readback ~ 5082. LCF ~ 750. XTAL Period = 1/28.63636MHz = 34.9ns
=> Tline of video = (5082 x 34.9ns) / 8 = 22.22us.
T frame of video = 22.22us x 750 = 16.667ms
=> Refresh Rate = 60Hz
