S video is it better than SCART? [Archive]

green granite

14th Jan 2010, 18:50

Not necessarily it depends which pins are connected at each end, just try it and see what it's like. But s-vid will probably be no better anyway.

Nicked from another site:

Signals are stored digitally on DVDs in a natural component form. This is also known as colourstream (colorstream?) or YPbPr colour difference. Component is a high quality interface. It is an American system. It comes in interlaced and progressive versions. It is cheap, reliable and high quality. Cables are also cheap.

RGB is another high quality interface. It also comes in interlaced and progressive versions. It is most commonly seen on computers where we use a 5-connection system RGBHV (Red Green Blue Horizontal sync Vertical sync). It is how most computer monitors are driven (HD 15 connector to CRT monitor showing VGA, SVGA, XGA etc are all RGBHV). There are numerous other versions. A 4 wire one where the sync signals are combines. A three wire hides the sync signal on one of the colour signal. RGB signals in general come through a variety of physical connector. The best are BNCs, then we have ordinary RCA / Phono plugs all the way down to SCARTs (the worst connector in the world?), designed by a committee (quote Ian J!). I think we can blame the French for hoisting this one on us, as previously it was known as a Peritel connector. It uses RGsB on some of its 21 pins. This is an interlaced ONLY version, the Gs means a sync signal on the G. The connector also has the ability to transfer Svideo and composite as well. It really is the lowest of the low re RGB signals. Signal levels are lower than other RGB signals and are therefore not easily matched / interfaced without additional electronics. (Scart to projector / plasma (without SCARTs sockets themselves) is a no no without additional electronics).

To be strictly accurate RGB is a component signal, however in reality the day to day terminology is different. Component refers to YPbPr (USA) signals and RGB is usually UK Scart RGB.

To get a RGsB Scart signal a conversion needs to take place within the DVD player. This is easily accomplished with MINIMUM degradation. However many TVs manufacturers are international now and use internal chipsets to make the TVs. This means that much of the digital wizardry is done internally in a natural component form (NTSC based American world) (this is why Lowe TVs can accept either RGB or Component via a non-standard Scart). This means that the RGB Scart signals need to transpose back into component. Again not difficult but not really necessary.

Now we need to look a bit closer at the difference between RGB and component. Basically component signals are LESS susceptible to colour errors (instability and phase) than their RGB brothers. Feed either to a PAL TV and you really shouldn’t see much difference (other than the extra stage of conversion the RGB Scart signal needs to go through to be converted into component internally). Look for TV with native component inputs is good advice. PAL is actually a very nice system and is more robust. The American use NTSC and this isn’t as robust. They NEED component signals to keep quality. Feeds them a RGB signal and NTSC suffers from colour instability problems in comparison. Hence, NTSC Never Twice the Same Color! These are the reasons why I recommend component over Scart RGB. It is easily demonstrated. Add into the equation that PROPER component cables are cheap (well-screened 75 ohm co-ax, 50p / m?) it starts to look very rosy against you silver wired RA Scart for £250. Hells even the £50 IXOS / QED SCARTs looks expensive in comparison.

For transferring DVD signal I recommend component signals. For transfer higher resolution signals (scaler to projector) I recommend proper RGBHV. Given the preference I would do all on BNCs.

Svideo can be best thought of as a cut down 2-wire version of component. It therefore retains many of the advantages of component signals. It is a stable system that works with both NTSC and PAL. Some players like Tag and Toshiba’s have been shown to have better Svideo performance than any RGB Scart for just these reasons. It is down to the quality of engineering. Again the internal TV chipsets are more SVideo aware than RGB Scart aware. We are now in the realms of bigger differences between the connectors than the interface standard. SCARTs are really bad, with emphasis on BAD, phonos are better, Svideo mini din is a bit better again but by far the best connector is the BNC. This is why top products will output EVEN their Svideo signal on BNCs given the option. My Tag can output a Svideo signal on 2 mini dins and a pair on BNCs (for ultimate quality on Svideo).

At the bottom of the pile is the poor old composite signal. It is actually not as bad as many want to make out. Don’t forget this is what analogue TV a laserdiscs use. It can produce an excellent picture in it’s own right so don’t dismiss some just because it only as composite. Ever seen the Arcam TV box at play? It is composite.

Any conversions in either direction will cause degradations, as will any cheap switching box. However when done well you should not be able to see any degradation to the signal (most receivers nowadays will pass interlaced signals with no visible degradation). Unfortunately the reality is there are more conversions going on than we perhaps realise.

A rule of thumb

Component > RGB Scart <> Svideo > composite

This is the best order on interfaces but connectors / engineering / transposing formats can certainly reverse at least the middle two Svideo and RGB Scart.