Very small image on 720p channels

[MikeD105]

I've got kind of a crazy question about a problem I had when setting up my uncle's new HDTV. Here goes nothing.

My uncle just purchased a Sony Bravia KDL46V5100 which i helped him set up. We have the HD cable box connected to the TV with HDMI. The cable box is a Scientific Atlanta 8300HD. Within the settings of the cable box there is a Picture Format setting which has the following choices: Fixed, Upconvert 1, Upconvert 2, and Auto DVI/HDMI. By default it was set for Fixed and set to output at 1080i. The TV aspect setting has choices such as Standard, Zoom, Wide Zoom, and when it is receiving an HD signal, an additional option of Full Pixel is available. I chose the Full Pixel option, which works great on HD channels. However when we change to an SD channel the TV remains in Full Pixel mode (even though you cannot select it when starting off on an SD channel) and this is where the trouble starts. In this scenario we get a what I can best describe as seeing the edge of the picture only along the top of the screen. Its almost like there isn't a clean edge and you can see missing pixels.

To remedy this I started playing with the aforementioned Picture Format setting on the cable box and selected Auto DVI/HDMI and voila problem gone. You can tell that it is changing the resolution based on the incoming image and you see the indicator on the front of the cable box change from 480i to 480p to 1080i, etc. You no longer get those wonky pixels at the top on SD channels and the TV actually switches to and from Full Pixel mode at the appropriate times.

Alas, a new problem arose and that being whenever I change to an HD channel being broadcast in 720p the picture gets incredibly small. This is not letterboxing, the picture only appears in an area in the middle of the screen taking up maybe 20-25% of the screen.

I've never seen something like this and I've done this sort of thing quite a bit. Any thoughts?

Sorry for the long post and thanks for taking the time.
__________________

 

[Adam]

I'll have to look into the issue of having a small image with 720p, but I can give some info on the white lines that you are seeing at the top of SD channels. That is most likely the closed captioning information. If your set is using overscan, you won't see that - but with a Full Pixel option, you will. Have you tried the "Full" picture option on the TV?

 

[MikeD105]

Yes I have tried the Full option and it does fix the problem. Although it is annoying to have to manually change the aspect every time you switch from an HD channel to an SD channel and then back again when you go back to an HD channel.

I'd much prefer to use that Auto DVI/HDMI Picture Format setting on the cable box which switches if for me. Just need to get around this small picture issue.

Could this have anything to do with that wizard feature in the cable box?

 

[Adam]

Can't you still use the "Auto DVI/HDMI" feature on the cable box with the "Full" setting on the TV? That's what I was talking about. I'm sure that you've tried that, but you have me curious. Thanks.

 

[bandphan]

try the component outputs and check the 720p setting

 

[Hi Ho]

If you have the cable box resolution set to "fixed" then there is no way for the TV to know when you are getting an SD signal. It is always getting whatever resolution the cable box is set to output. You need to find a setting in the cable box that outputs HD at one resolution and SD at another. Then the TV aspect settings will work. I have never used a Scientific Atlanta cable box so I do not know what settings to change.

As for the 720p picture being small; Have you taken it out of full pixel mode? 1:1 pixel mapping of a 720p image on a 1080p display will result in a small picture because there is no scaling going on. I would not recommend full pixel mode on TV broadcasts. It is useful when using the TV as a PC monitor but not for watching TV. You aren't missing anything with a little overscan and TV programs are framed with overscan in mind.

 

[MikeD105]

Can't you still use the "Auto DVI/HDMI" feature on the cable box with the "Full" setting on the TV? That's what I was talking about. I'm sure that you've tried that, but you have me curious. Thanks.

I believe I did try that, but whenever I use the Auto DVI/HDMI setting I get the small picture regardless of the aspect setting on the TV. I'm planning on going over there again tomorrow so I'll play with the settings some more and let you know what happens. I'm also going to play with the cable box wizard to see if playing with those settings do anything either.

try the component outputs and check the 720p setting

Another good suggestion. I'll give that a try as well.

Thanks all.

 

[MikeD105]

OK I fixed it!

Sorry for the super long delay in getting back to this. Here's what I did:

I made sure I was on an HD channel and set the TV aspect setting to Full Pixel. Then set the cable box Picture Format setting to Upconvert1. Someone on another board said that the Upconvert1 setting will up convert to 1080i, so I gave that a shot. Now on all HD channels I get the correct picture size and when I switch to an SD channel the TV aspect setting automatically reverts to Full and again gives me the correct image size and does not give me those horrible distorted pixels at the edge of the screen.

Basically that Full Pixel mode on the tv wants to use only the full resolution capabilities so any 720p broadcast comes up small because that's how it would appear in that resolution. By switching the cable box to Upconvert1 the box upconverts 720p images to 1080i solving the problem. I really thought I had tried doing that on the first go round, but I guess things got a little crazy.

Anyway, again thanks so much for the advice and sorry for the slow response.

-Mike