VoyForums
[ Show ]
Support VoyForums
[ Shrink ]
VoyForums Announcement: Programming and providing support for this service has been a labor of love since 1997. We are one of the few services online who values our users' privacy, and have never sold your information. We have even fought hard to defend your privacy in legal cases; however, we've done it with almost no financial support -- paying out of pocket to continue providing the service. Due to the issues imposed on us by advertisers, we also stopped hosting most ads on the forums many years ago. We hope you appreciate our efforts.

Show your support by donating any amount. (Note: We are still technically a for-profit company, so your contribution is not tax-deductible.) PayPal Acct: Feedback:

Donate to VoyForums (PayPal):

[ Login ] [ Contact Forum Admin ] [ Main index ] [ Post a new message ] [ Search | Check update time | Archives: 1, 2, 3, 4, 5, 6, 7, [8], 9 ]

[ Next Thread | Previous Thread | Next Message | Previous Message ]

Date Posted: 04:45:03 02/16/02 Sat
Author: Potter
Subject: Re: Blanking durring VBI
In reply to: Jain 's message, "Blanking durring VBI" on 06:03:50 02/15/02 Fri

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

[ Next Thread | Previous Thread | Next Message | Previous Message ]

Replies:

[ Contact Forum Admin ]

Forum timezone: GMT-8
VF Version: 3.00b, ConfDB:
Before posting please read our privacy policy.
VoyForums(tm) is a Free Service from Voyager Info-Systems.
Copyright © 1998-2019 Voyager Info-Systems. All Rights Reserved.