High Def Forum
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Component Switchbox Issues

05-15-2006, 09:38 PM
I own a RCA 38" CRTV that runs native 480p and 1080i HD resolutions.
Until recently I've been using a low end Sony composite switchbox to switch my component devices without any issue. I used a seperate manual non-powered 4 switcher and a seperate manual non-powered optical switcher and its been working fine. I had been running mixed devices running both 480p and 1080i.

Recently however I found that 4 inputs wasn't enough so I ordered THIS (http://www.joytech.net/products.php?section=viewprod&productID=79&lang=1&catID=9). So I hooked it up and found it running 1080i signals fine. However, when I went to use 480p devices I found I was getting a smearing and fuzz out at the top of the screen. Not so much on static images but when the picture would have quick motion it would completely tear up. I tested the old box again and that works fine still. This new powered unit however is not, and for the life of me I don't know why.Its odd that 1080i would run thru it fine but 480p won't. Any help would be appreciated.

05-16-2006, 08:02 AM
I would guess it's a defective unit, but the spec does refer to "Advanced Signal Technology"--what do they mean by that? Are they upscaling the 480p material to 1080i? If so, it could be a bug in their scaler.

How does it look on 480i material?

05-16-2006, 08:05 AM
Its not a scaler. Just a switch unit. Doesn't manage signal increase of decrease.

05-16-2006, 08:13 AM
So how does it look on 480i? Same problem?

05-16-2006, 09:52 AM
Don't know. Will check it tonight. Is there a signal bandwidth difference between progressive and interlaced that would cause the issue?

05-16-2006, 11:42 AM
It depends on your source. If the progressive source is bobbing each field of a 480i signal to a 480 line frame at 60 frames-per-second, it is twice the bandwidth compared to weaving the two fields into a 480 line frame at 30 frames-per-second.

I don't know what your source is. A DVD player wouldn't do that on film content. If you're supplying a 480p/60 signal from some source, that would be twice the bandwidth as a 480i/30 signal.

In either case it would still be less bandwidth than 1080i/30. It's hard to imagine how the problem would only affect the top of the screen and not the rest if it was a bandwidth problem. Perhaps the switcher is distorting the sync signals enough that the TV is getting out of sync at the start of the frame but eventually locking in?