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ADV7188 Secam colour noise and missing video line

Question asked by Nina on Oct 12, 2012
Latest reply on Oct 29, 2012 by DaveD


I have two problems with the ADV7188 in secam mode.


First problem is colour noise at line 23-26 (so just after VBI area). This noise is there all the time, even if a black picture is decoded. It starts from beginning of line 23 (WSS) and slowly disappears accross lines up to 26.  It seems to be related to the transition from VBI area to active video. (This colour noise is not apparent in the evaluation kit, but the evaluation kit outputs the lines incorrectly. All lines is shifted two lines up, so that WSS is at line 21. This means that most of the noise will be outside active area).

With register 0xEB or 0xEC, I can delay the position of the first active line, and that seems to help, but I dont understand why? The lines are still present from 23 and uppwards, but the noise is gone and the first lines become black and white. Seems like it has something to do with the comb filters?


Second problem is that when I use the VBI_EN, to get the VBI data through with minimum filtering, the last part of line L335 and and the beginning of line 23 is missing (becomes black). Same happends with the evaluation board. This must be some kind of bug?


All replies are greatly appreciated!