Line-Blanking interval of AD7390's output

According to the table 1-1 in ITU-R BT.470-6,  the line-blanking interval of PAL B/D/H/I/K/L should be 12us:

   

But when I measure  the output of ADV7390, I found that it is about 10us.  I have config ADV7390 by using the scripts in table 82.  I think this is correct for ADV7390 when the input is set to BT656, because according to figure 104 in datasheet, the line-blanking interval should be 288 clock ( frequency is 27MHz and period is 37.037ns)  , that is 288 x 37.037 = 10.6us.

But it is not conform to th BT470, and have ariased problems in some monitors ( most monitor  is OK).  How can I changed the line blanking interval to 12us?

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  • Dear Jeyasudha.M,

            Thank you for your quick reply.  I have check that thread but it is not my case. The input clock of ADV7390 in my system is 27MHz.  I searched in the datasheet and found that bit3 of Reg#0x84(SD active video length)  can solve this problem. When setting active pixel to 702 pixel  by enable this bit,  the line-blanking interval is exactly 12us now. But I worry that the angle of view will be incorrect because the camera output 720 pixel and ADV7390 discard 18 of them. Should I add a scaler before AD7390 to scale 720 pixel down to 702 pixel?  Could you explain this bit in detail ? For example, how it is implement,  discard pixel or scale-down in AD7390?  In what circumstance I  should enable it, and  if it is enable , any other reigster should  be changed?  and so on.  Thanks in advance.

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  • Dear Jeyasudha.M,

            Thank you for your quick reply.  I have check that thread but it is not my case. The input clock of ADV7390 in my system is 27MHz.  I searched in the datasheet and found that bit3 of Reg#0x84(SD active video length)  can solve this problem. When setting active pixel to 702 pixel  by enable this bit,  the line-blanking interval is exactly 12us now. But I worry that the angle of view will be incorrect because the camera output 720 pixel and ADV7390 discard 18 of them. Should I add a scaler before AD7390 to scale 720 pixel down to 702 pixel?  Could you explain this bit in detail ? For example, how it is implement,  discard pixel or scale-down in AD7390?  In what circumstance I  should enable it, and  if it is enable , any other reigster should  be changed?  and so on.  Thanks in advance.

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