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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  • Hi chiguoqan,

    Setting the SD active video length bit to 1 will reduce the horizontal pixel length from 720 to 702 for PAL video. No other bit needs to be set for this functionality to be enabled. There is no scaler in the ADV7390, so these 18 pixels are essentially discarded. A scaler could be used before the encoder if you require all active video to be shown, but this is not essential.

    Since you mentioned you were using a camera as an input, it might be worth checking that the pixel clock frequency is 27MHz as some cameras give out a 28.375 MHz pixel clock, which the encoder cannot support. See the EngineerZone link attached for information regarding this:

    [ADV7391] PAL Output 

    Best Regards,

    Anthony

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  • Hi chiguoqan,

    Setting the SD active video length bit to 1 will reduce the horizontal pixel length from 720 to 702 for PAL video. No other bit needs to be set for this functionality to be enabled. There is no scaler in the ADV7390, so these 18 pixels are essentially discarded. A scaler could be used before the encoder if you require all active video to be shown, but this is not essential.

    Since you mentioned you were using a camera as an input, it might be worth checking that the pixel clock frequency is 27MHz as some cameras give out a 28.375 MHz pixel clock, which the encoder cannot support. See the EngineerZone link attached for information regarding this:

    [ADV7391] PAL Output 

    Best Regards,

    Anthony

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