During vertical blanking intervals, does the ADV7441A produce at its output samples of the 'raw VBI' signal? Or, is the only way to get VBI data is by use of the VBI processors?
Not exactly a common thing but it's possible.
To achieve this on the decoder, first ensure that no filtering or combing of the VBI region is performed:
VBI_EN Vertical Blanking Interval Data Enable (SDP), Address 03h,  (Set to 1'b1 All data for lines are passed through unfiltered and available at the output port)
No Chroma information should be available during the VBI region, if the (ADI) encoder detects what it sees as chroma information it will re-modulate it onto the luma channel and corrupt the VBI pass through data, for this reason it is also advisable to blank the Cb and Cr samples during the VBI region:
BL_C_VBI Blank Chroma during VBI (SDP), Address 04h, (Set to 1'b1 to blank Chroma values. Default)
The above writes to the decoder ensure that VBI data is output through it unfiltered and undistorted.
The manual indicates that VBI_EN is for the SDP. For the component processor, it is not clear that VBI lines are passed thru or blanked by the CP. Please verify.
It's DE_BLANK_EN for the CP.
I believe on the ADV7441A, its called AV_BLANK_EN:
0 - Output clamped and gained data during the horizontal and vertical blanking time1 - Replaces data in horizontal and vertical blanking period with default values
0 - Output clamped and gained data during the horizontal and vertical blanking time
1 - Replaces data in horizontal and vertical blanking period with default values
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