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Old November 18th, 2002, 12:55 AM   #1
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Component/S-video and projection quality

Ken Barnes wrote in another thread:

"DVD's look pretty good even through S-video, which is the connection that I will also be using... (clip)... But a component signal is so much better...(clip)...Most decent DVD players have a component out and if you plan to burn a DVD from your movie, the image should be projected better."

Is this generally true?
How significant is the difference?
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Old November 18th, 2002, 09:05 AM   #2
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Technically spoken there is no doubt that avoiding color coding (NTSC or PAL) which is needed for S-video is the correct way to go. There are however so many tricks, display device performance issues, and image content depending elements, that make that S-video "looks pretty good...". If you use a recent higher end large screen TV or projector you will see a signifcant difference.. If you look on a smal TV set eventually with artificial sharpening you will find S- video pretty good an on some (low res and low contrast ) images even better than components
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Old November 18th, 2002, 09:47 AM   #3
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What about differences when using DVD player and an average LCD projector on a "big" screen (3+ meters).

Should I use S-video or composite?
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Old November 18th, 2002, 10:06 AM   #4
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Go for components if yr projector has the inputs, especially in a PAL land (Finland)
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Old November 19th, 2002, 10:14 AM   #5
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Keep in mind that if you go with Component RGB that you are
doing a colorspace conversion (TWICE!). This WILL alter the
color when you are watching it. For this reason i prefer S-Video
myself.
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Old November 19th, 2002, 01:38 PM   #6
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Sorry Rob, but "colorspace conversion" is something else, and not related, neither to S-video, nor to component processing. The reason why component is better is because the signal doen't have to go through an extra color encoding (NTSC or PAL) and decoding step, which both reduce the signal quality.
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Old November 20th, 2002, 02:14 AM   #7
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Well... either I'm indeed very much mistaken here... or...

Let me explain. DV and also MPEG (for VCD, SVCD & DVD) use
a YUV based compression. Since S-Video is Y-C you do not have
to convert. Since component is RGB you must convert YUV to
RGB and in the TV back to Y-C/YUV.

These conversions should lead to slight changes in the color.

Now I could be completely wrong with this ofcourse....
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Old November 20th, 2002, 02:51 AM   #8
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Rob sorry, you are wrong.

component = YUV

RGB= rgb, which is almost always via a scart connector and only available in PAL lands.

kermie
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Old November 20th, 2002, 05:05 AM   #9
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Rob, FYI,
You are right about the YUV based compression for DVD and most other dig video streams (DVD is MPEG2 compressed, 4:2:0 worldwide). In any case, if you want to display that signal starting from the DVD disc , you have of course to decompress (into YUV) Now, all displays finally need RGB (on the LCD panels in case of an LCD projector). You can get this final format just by transforming the YUV into RGB, somewhere in the signal chain. This can be done in the DVD player and the interconnection is then an RGB one which goes "straight" into the display device(LCD). This 1 to 1 YUV to RGB linear transformation (therefore it's not a real colorspace conversion) can also be performed in the display device itself...In this case the player is connected through YUV . The Y/C path uses extra color modulation (in the player) and demodulation (in the diplay device). The start (decompressed YUV) and the final signal (RGB) is the same as in the component situation, but the signal quality is being lowered because by these two intermediate steps.
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Old November 20th, 2002, 07:32 AM   #10
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Hmmm.. okay. I stand corrected... Don't know where I got this
information, but I truly thought it was that way. Oh well, we learn
every day!

Thanks!
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