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Standard Definition: Component vs RGB SCART ? |
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#1 |
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Standard Definition: Component vs RGB SCART ?
Hi.
I was just wondering if there was much difference between component video and RGB SCART on standard definition TV signals? I know some standard def TV sets had component inputs (such as the Toshiba series), but couldn't accept any HD signals (not even 480p). Does anyone have any information? Does component actually offer a (significantly) higher quality signal than RGB, or was it *only* ever used due to its higher (HD-capable) bandwidth? |
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#2 |
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Component and RGB are effectively equivalent and you can convert between them fairly easily.
On a domestic basis, you probably won't notice any difference between component and RGB. Conversion is easy if you think of component as being Y (Luminance), and two colour difference signals (R-Y and B-Y). From that you can use simple maths to change between RGB and YUV. |
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#3 |
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Quote:
Component and RGB are effectively equivalent and you can convert between them fairly easily.
On a domestic basis, you probably won't notice any difference between component and RGB. Conversion is easy if you think of component as being Y (Luminance), and two colour difference signals (R-Y and B-Y). From that you can use simple maths to change between RGB and YUV. I remember hearing something along those lines (and this apparently frees up the bandwidth, allowing >576i signals to be carried). I still don't get the maths behind how that works, but I guess if it works, it works! |
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#4 |
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So component is basically just RGB, but with the "master" value only transmitted along the 'R' wire, and the other two only carrying the "delta" (difference) values?
I remember hearing something along those lines (and this apparently frees up the bandwidth, allowing >576i signals to be carried). I still don't get the maths behind how that works, but I guess if it works, it works! Broadcast uses this because of the way digitisation from analogue to digital is done, and the Y signal is sampled a 4 times the frequency of the colour difference signals. Both YUV and RGB are perfectly capable of carrying High Definition signals. |
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#5 |
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Quote:
Similar, though in practice the Y (black/white) signal is carried on the Yellow cable, or Green if using RGB cables. U and V signals use the R and B cables.
Broadcast uses this because of the way digitisation from analogue to digital is done, and the Y signal is sampled a 4 times the frequency of the colour difference signals. Both YUV and RGB are perfectly capable of carrying High Definition signals. |
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#6 |
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RGB on a SCART has no technical reason it can't handle HD signals. However, there is no equipment on the market that can handle HD over SCART RGB that I know of.
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#7 |
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RGB on a SCART has no technical reason it can't handle HD signals. However, there is no equipment on the market that can handle HD over SCART RGB that I know of.
I thought there was a technical issue (to do with the "redundancy" of having 3 nigh-identical signals being sent concurrently) that prevented RGB SCART from being able to handle HD? And where does composite/S-Video and our good old friend RF fit into all this?
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#8 |
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Nope, no technical reason why a SCART connector couldn't handle an HD signal.
Convention seems to have decided that HD component will be either RGB or YUV (usually the TV set will be switchable) carried over a set of 3 phono cables. S Video is poorer quality than RGB, as it carries the Y separately, and the other cable carries a multiplexed version of the two colour-difference signals. Composite is the worst of the lot, which carries the Y signal, and the colour difference signals all multiplexed onto the same cable. Incidentaly, composite is also capable of carrying an HD signal - we've used some old black and white 1050-line (IIRC) analogue HD widescreen monitors before at work, that were used to display the budget to the studios and galleries (was the only way to get the budget to all users, as we were not permitted to make copies of the document, or to see pages before the chancellor starts to read them). |
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#9 |
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Quote:
Incidentaly, composite is also capable of carrying an HD signal - we've used some old black and white 1050-line (IIRC) analogue HD widescreen monitors before at work, that were used to display the budget to the studios and galleries (was the only way to get the budget to all users, as we were not permitted to make copies of the document, or to see pages before the chancellor starts to read them).
![]() Quote:
Originally Posted by tellytart1
Composite is the worst of the lot, which carries the Y signal, and the colour difference signals all multiplexed onto the same cable.
Btw that's a good point about the 'old' HD formats.... they must have been carried using "old" cable connections, so it makes one wonder why TV manufacturers insist on using component video for 720p/1080p :S |
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#10 |
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Do you work in parliament???
![]() Quote:
Originally Posted by bookerg
What's the difference between composite and RF? Is it just the case that RF = composite + mono audio? Or is there more to it?
Quote:
Originally Posted by bookerg
Btw that's a good point about the 'old' HD formats.... they must have been carried using "old" cable connections, so it makes one wonder why studios insist on using component video for 720p/1080p :S
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#11 |
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Because there's only so much bandwidth you can get out of a single composite cable. The old analogue HD format we use is black & white only!
(1) Wouldn't using a composite cable diminish the whole purpose of having a super-sharp 1050-line image? I would've thought a composite 1050-line image would still look weak compared to an RGB 576i image..... or is it just the case that - as it's only B&W - it renders the whole composite/RGB argument obsolete? (as only one wire is basically needed) (2) So there *is* a bandwith issue preventing certain cables carrying HD? ![]() RGB definitely isn't one of the victims? oh, and:- (3) Just out of interest, roughly what year were these TVs in use at your office? Were they ever at any point discarded (i.e. in favour of standard definition), or did they last right up until the "new" HD formats arrived in recent years? |
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#12 |
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OK.
1) No, depends on the sending and receiving equipment, and length of cable. (The longer the cable the worse it'll look) 2) There's a bandwidth issue with any cable carrying a signal - make the cable long enough and the signal will degrade. The higher the bandwidth of the signal you're sending, the shorter the cable will be before the signal degrades. SDI (Serial Digital - the standard definition format used by just about any broadcaster for signal movement within studios) has a transmission rate of 270Mbs (yep, nearly 3 time faster than 100meg ethernet), and using SDI grade cabling, the signal will only travel for between 300 and 350 metres before the signal has degraded too much to be able to be decoded. There is also an HD format, called HD-SDI, which can use the same cabling, but will only travel for about 100 metres before it degrades too far to be decoded again. 3) They were used last time we did a budget special, in 1996. |
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#13 |
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Quote:
So component is basically just RGB, but with the "master" value only transmitted along the 'Y' (green?) wire, and the other two only carrying the "delta" (difference) values?
I remember hearing something along those lines (and this apparently frees up the bandwidth, allowing >576i signals to be carried). I still don't get the maths behind how that works, but I guess if it works, it works! Y (Luminance) =R+G+B |
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#14 |
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The maths is quite simple unfortunately I think Tellytart forgot to add the other part of the information
Y (Luminance) =R+G+B Y=0.299*R + 0.587*G + 0.114*B U=0.436*(B-Y)/(1-0.114) V=0.615*(R-Y)/(1-0.299) |
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#15 |
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Quote:
Incidentaly, composite is also capable of carrying an HD signal - we've used some old black and white 1050-line (IIRC) analogue HD widescreen monitors before at work, that were used to display the budget to the studios and galleries (was the only way to get the budget to all users, as we were not permitted to make copies of the document, or to see pages before the chancellor starts to read them). |
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#16 |
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I just thought I'd add that component can be progressive, this alone can make a big difference depending on the makeup of the different pieces of equipment.
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#17 |
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Not quite, there are scaling factors involved to generate the Y signal from RGB:
Y=0.299*R + 0.587*G + 0.114*B U=0.436*(B-Y)/(1-0.114) V=0.615*(R-Y)/(1-0.299) Edit -No its the lack of rationalisation of the denominator for U and V giving U=0.492*(B-Y) V=0.877*(R-Y) Which numbers I recognise. |
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#18 |
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Yep, I was going from Wikipedia which was showing the more complex formulae, as I couldn't remember the number off the top of my head!
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#19 |
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I thought there was a technical issue (to do with the "redundancy" of having 3 nigh-identical signals being sent concurrently) that prevented RGB SCART from being able to handle HD?
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#20 |
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I just thought I'd add that component can be progressive, this alone can make a big difference depending on the makeup of the different pieces of equipment.
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#21 |
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No technical reason, just that HD is American, and America uses Component and not RGB - so all the HD gear has been Component because it's originally of American origin. Once you've got HD sources with Component, and HDTV's with Component, there's really very little purpose in modifying RGB SCART to accept HD. In any case, Component is near enough obselete, having been superceded by HDMI.
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#22 |
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Again though, there's nothing stopping RGB being progressive either, merely that the Americans didn't use RGB so it was never developed.
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#23 |
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Nope, no technical reason why a SCART connector couldn't handle an HD signal.
Convention seems to have decided that HD component will be either RGB or YUV (usually the TV set will be switchable) carried over a set of 3 phono cables. S Video is poorer quality than RGB, as it carries the Y separately, and the other cable carries a multiplexed version of the two colour-difference signals. Composite is the worst of the lot, which carries the Y signal, and the colour difference signals all multiplexed onto the same cable. Incidentaly, composite is also capable of carrying an HD signal - we've used some old black and white 1050-line (IIRC) analogue HD widescreen monitors before at work, that were used to display the budget to the studios and galleries (was the only way to get the budget to all users, as we were not permitted to make copies of the document, or to see pages before the chancellor starts to read them). I always thought it was just another con by manufacturers to make us shell out more money for a new port on the same TV. So, theres no reason why HD cant go through a Scart eh? This is interesting... |
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#24 |
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So, theres no reason why HD cant go through a Scart eh? This is interesting...
![]() I mean, you could technically send a component signal down a 21-pin SCART lead (merely swapping the R,G,B pins on the device's end for Y,U,V and re-configuring a TV to do the same).... but what I mean is, could a device (such as, say, a SNES) still output the *exact* same RGB-through-SCART signal it always did, but do it in HD, or at least 480p? (ignoring, for the sake of argument, the fact that a SNES probably couldn't ever handle HD) |
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#25 |
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I myself am a little confused by exactly what "HD-through-SCART" means
![]() I mean, you could technically send a component signal down a 21-pin SCART lead (merely swapping the R,G,B pins on the device's end for Y,U,V and re-configuring a TV to do the same).... but what I mean is, could a device (such as, say, a SNES) still output the *exact* same RGB-through-SCART signal it always did, but do it in HD, or at least 480p? (ignoring, for the sake of argument, the fact that a SNES probably couldn't ever handle HD) The main reason for HDMI being pushed is copy protection, the fact it's digital is a big advantage but not the huge one some would like to think. |
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