we use the ADV7181C for teletext decoding (-> 656 data stream). Normally it works very well. Now we have some sources which seems not to have the ideal signal levels: single bits (higher frequencies) are only 80% of the static level (see screenshot). When using this teletext sources some there is a good visible error rate (1 : 500). Filters like the IF-Filter seems not to take affect on the VBI-lines. Are there any (hidden, non documented registers) where we can manipulate the filtering, gaining etc. of the VBI-lines before VDP?