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ADV7401 Analogue RGB Input Discoloration

Question asked by Theuns on Jan 31, 2017
Latest reply on Jun 12, 2017 by DerekBurke

Hi all,


We have a custom video board utilizing the ADV7401 to receive various input video signals. In one configuration we receive analogue RGB via VGA cable. In this specific example we are passing XGA 1024x768 60Hz through the board. The output of the decoder is configured for 16-Bit interleaved PrPb.


Using the default configuration for this resolution as seen in Table 154 in the ADV7401 manual on page 329, we see discoloration. It seems that the color black is outputted as green. Please see attached images for reference. Also attached is the configuration script. The attachments show a windows XP screen with a normal background and with a black background showing as green.


By manually configuring the AGC, CP Offsets and also the any-to-any color space converter we are able to achieve much better visuals (Black is almost completely black however there is still a slight green tint). I cannot easily find the correct manual configurations for these 3 CP blocks to produce the perfect colors.


My question is, why does the automatic configurations for AGC, CP Offsets and color space converter produce this discoloration? It seems nearly impossible to find the correct manual settings for these 3 CP blocks to produce the correct colors. Also will the manual configuration of these blocks not result in different visuals for different sources?  


I have a schematic diagram for the decoder implementation on our board, however I am not allowed to share this with all and will need to directly share with an Analog support engineer. 


Any advice or help will be appreciated.