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Date Posted: 06:00:30 02/18/02 Mon
Author: Jain
Subject: Re: Blanking durring VBI
In reply to: Potter 's message, "Re: Blanking durring VBI" on 04:45:03 02/16/02 Sat

In my previous message, read: "...(I mean output "Normal" in 1 all the time for unscrambled channels)"
J
>Hi
>That sounds like a fairly easy change - to get the pic
>to pass the actual signal instead of inserting black
>on non-visible lines. In MAINLOOP a flag is set for
>MAKEHLINE to create black on the non-visible lines
>(PASSBLACK) and it's reset at the start of the visible
>lines. In MAKEHLINE at the end of the burst period
>this flag is checked and if set it causes an
>artificial black to be inserted something like this:
> movlw VIDEOOUT
> btfsc VIDSMODE,DOINVERT ; IF we have to invert
> movlw INVERTIT ; make invert
> btfsc VIDSMODE,PASBLACK ; IF we have to make
>black
> movlw BLACKOUT ; make BLACK ****HERE****
> btfss VIDSMODE,VIDEOKAY ; IF not decoding
> movlw VIDEOOUT ; just pass video
> movwf PORTB ; ACTIVE VIDEO LINE BEGINS
>If you change the movlw BLACKOUT to movlw VIDEOOUT the
>actual black level will pass but includes all
>extraneous data on the signal as well (data packets,
>teletext, macrovision, noise etc etc). Sync
>regeneration and burst handling are not affected and
>MAKEVBI will still insert artificial black unless the
>same change is made in there as well. Individual
>lines may be handled differently by expanding MAINLOOP
>and setting the flags however you need.
>PS after looking at my coding (lost in the codewoods)
>it may be that what I decribed to you earlier was
>wrong and I'm not sampling a true black level after
>all as that was an earlier incarnation - more late
>nights to come.
>
>
>>Is there any code (for NTSC) that doesn't put blanking
>>pulse from PIC in 1 durring VBI (but only durring
>>synchro part of the line, including VBI)?
>>Jain

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