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Ntsc Vs Pal On Xbox (gamma & Alignment Issues)


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#1 PsychoNavigator

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Posted 22 April 2010 - 12:33 PM

So I've been experimenting with my new HD cables and in the search to attempt to figfure out another issue, I came across the suggestion of changing the PAL signal to NTSC to enable the higher resolutions.

With PAL, I have a nice solid black picture and everything is centered properly, but when I change it to NTSC, the blacks are a light grey and some information that should be onscreen disappears at the bottom.

I've looked for NTSC/PAL settings on my TV, and I don't seem to see anything regarding that.

Should I recalibrate my screen settings and adjust the gamma (I think that's in there somewhere in XBMC) of just not bother?

#2 Heimdall

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Posted 22 April 2010 - 01:26 PM

Changing PAL to NTSC to enable higher resolutions isn't a suggestion - it's mandatory!

Welcome to the world of old TV broadcast standards. NTSC colours are washed out compared to PAL (from memory the dynamic range for NTSC luminance is lower, and NTSC luminance doesn't go down to zero, it starts at a higher level i.e. black is never better than very dark grey - there's always a small luminance signal). There is nothing you can do about it when using composite - the standard is fixed - but when you use component cables (HD) the problem doesn't exist because the signal isn't NTSC any more, it's YPbPr (a different standard - think of it as a variant of RGB).

For the screen size there is a similar story. It's all to do with overscan and the way NTSC typically has less overscan than PAL does (it's related to the linearity of old analogue TV CRTs and edge effects in the CRT tube, and the drive for optimum picture quality on affordable TV sets - have a look at Wikipedia if you're really interested). The net effect is that the screen seems to be a different size when you switch from PAL to NTSC. UnleashX and XBMC both allow you to resize the screen - a quick search through system settings will get you to the "Screen Calibration" screens for either dash. However, again, you will need to do this separately once you start to use component (HD), because the scan settings are different. The bottom line is that TV signals are analogue, and NTSC, PAL and component (HD) are all different, so you need to make "analogue" adjustments when you switch between them.

#3 PsychoNavigator

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Posted 23 April 2010 - 01:36 PM

QUOTE(Heimdall @ Apr 22 2010, 10:26 PM) View Post

Changing PAL to NTSC to enable higher resolutions isn't a suggestion - it's mandatory!

Welcome to the world of old TV broadcast standards. NTSC colours are washed out compared to PAL (from memory the dynamic range for NTSC luminance is lower, and NTSC luminance doesn't go down to zero, it starts at a higher level i.e. black is never better than very dark grey - there's always a small luminance signal). There is nothing you can do about it when using composite - the standard is fixed - but when you use component cables (HD) the problem doesn't exist because the signal isn't NTSC any more, it's YPbPr (a different standard - think of it as a variant of RGB).

For the screen size there is a similar story. It's all to do with overscan and the way NTSC typically has less overscan than PAL does (it's related to the linearity of old analogue TV CRTs and edge effects in the CRT tube, and the drive for optimum picture quality on affordable TV sets - have a look at Wikipedia if you're really interested). The net effect is that the screen seems to be a different size when you switch from PAL to NTSC. UnleashX and XBMC both allow you to resize the screen - a quick search through system settings will get you to the "Screen Calibration" screens for either dash. However, again, you will need to do this separately once you start to use component (HD), because the scan settings are different. The bottom line is that TV signals are analogue, and NTSC, PAL and component (HD) are all different, so you need to make "analogue" adjustments when you switch between them.


Okay, I changed it back over to NTSC again, and set it to 720p. I've got a 32" Samsung (not a full HD) so I'm assuming that should be sufficient. I also did the calibration. I'm never sure about the corners, I just set it so the lines just disappear, and visually try to square up the box.

Now my video files seem to be a bit weird in their aspect ratio but this warrants further research. It could just be that my sources arent a true 16:9, as in the black bars are included in the file itself.

Thanks for your post,





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