Log inRegister an accountBrowse CSDbHelp & documentationFacts & StatisticsThe forumsAvailable RSS-feeds on CSDbSupport CSDb Commodore 64 Scene Database
You are not logged in 
CSDb User Forums

Forums > C64 Coding > White Screen Bleeding Into Audio
2018-10-08 14:40

Registered: Mar 2007
Posts: 129
White Screen Bleeding Into Audio

This topic has come up a few times now with people I've spoken to ... but Google isn't helping me out here so I just want to make sure that I'm not totally mis-remembering history...

It's my belief that on C64, full-white screens and even screens with large blocks of white should be avoided due to some sort of audio distortion (on a REAL c64).

Was this an actual problem? (I believe it was.. I certainly saw/heard the problem on my C64 back in the day)

Was it particular to certain models of C64?

Was it particular to certain cables? I always used composite or aerial lead...

IIRC, Amiga didn't have this problem at all.

This would then lead into some follow questions... eg:-

- how much white is too much?

- will other bright colours cause this problem? Eg. light green? Off white? Yellow?
... 6 posts hidden. Click here to view all posts....
2018-10-08 18:34

Registered: Apr 2002
Posts: 4313
white screens were generally a big no no on the real thing. you got more noise from tv, and you got your eyes bleed and you couldnt see a thing. led display white is totally different light gray at best.
2018-10-10 00:25

Registered: Jul 2009
Posts: 272
ha. yes it was a well known feature of c64s on tvs of the day :)

I always wondered, at one point the crt emu of Vice would buzz like hell and warp the screen slightly when too much white was displayed :)
2018-10-10 00:32

Registered: Dec 2001
Posts: 8920
the buzz is there, enable "video to audio leak" :)
2018-10-10 03:53

Registered: Jul 2009
Posts: 272
2018-10-10 13:07

Registered: Jan 2018
Posts: 98
This is semi related I guess...
My TV (and I tried 2 different CRT TVs) get warped when there's a lot of white on the screen. Not just on C64 but also on Amiga500.
2018-10-10 13:55

Registered: Apr 2002
Posts: 1095
"On some monitors the image expands in bright areas and contracts in dimmer areas. This happens because the monitor has a poor high-voltage regulation. This effect is more or less visible in all monitors, but normally more so in very cheap monitor models, as it is not inexpensive to design and manufacture a very good high-voltage regulation system. If your monitor has a very bad screen regulation, the picture "zooms" when you adjust the brightness control."
2018-10-11 12:01

Registered: May 2004
Posts: 652
There is a full screen upscroller by Graham (Comalight12 or something?) to the music of 'sweet dreams' and it flashes white. That had a very cool zoom effect on my old big TV ;-)
2018-10-11 12:04

Registered: Dec 2001
Posts: 8920
the intro of cucumber juice 2 flashes white for the same reason :)
2018-10-11 16:37

Registered: Feb 2018
Posts: 2
Bizarrely, I actually remember that. I would avoid using a white border in my programs because I hated the way the screen would distort.

Funny the things you'll just accept when you're young and not question... Nowadays, I'd devote at least 2 hours into internet sleuthing trying to figure out why it's doing that and how to stop it.
2018-10-12 08:56

Registered: Dec 2001
Posts: 102
Audio bleeding also happens inside c64 voltage rails. SID-chip spec sheet states that separate voltage and gnd-lines should be used but Commodore shared them with VIC-II. This results very noisy +12v and +5v voltage lines to SID.

This is easily heard if you do in basic:

poke 53280,1:poke 53281,0

and turn up the volume. You can shut down display if you use line-out for audio to hear this same :)

It seems that in 8580's there's better insulation what comes into noisy voltages bleeding into audio output, but it can be heard there too, but not as loud as on 6581's
Previous - 1 | 2 - Next
RefreshSubscribe to this thread:

You need to be logged in to post in the forum.

Search the forum:
Search   for   in  
All times are CET.
Search CSDb
Users Online
Knight Rider/Excess
Guests online: 31
Top Demos
1 Uncensored  (9.7)
2 Comaland 100%  (9.7)
3 Unboxed  (9.7)
4 Edge of Disgrace  (9.7)
5 Coma Light 13  (9.6)
6 The Shores of Reflec..  (9.6)
7 Lunatico  (9.6)
8 Wonderland XII  (9.6)
9 X Marks the Spot  (9.6)
10 C=Bit 18  (9.6)
Top onefile Demos
1 Arok 20 Invitation  (9.6)
2 FMX Music Demo  (9.6)
3 Daah, Those Acid Pil..  (9.6)
4 Pandemoniac Part 2 o..  (9.5)
5 Rewind  (9.5)
6 Party Horse  (9.4)
7 Dawnfall V1.1  (9.4)
8 Crystal Gazer  (9.4)
9 Merry Xmas 2017  (9.4)
10 Dawnfall  (9.4)
Top Groups
1 Oxyron  (9.4)
2 Booze Design  (9.4)
3 Censor Design  (9.4)
4 Finnish Gold  (9.3)
5 The Transfer Team  (9.3)
Top NTSC-Fixers
1 Pudwerx  (10)
2 Horizon  (9.8)
3 The Mind Slayer  (9.8)
4 The Shadow  (9.7)
5 Stormbringer  (9.6)

Home - Disclaimer
Copyright © No Name 2001-2018
Page generated in: 0.058 sec.