S-Video Versus Component Video: Theory & Reality
By this time, most of us (atleast the tech-savy ones) have come to accept that by default, the component video format provides the best picture due to the Pb, Pr and Y signals being fed directly and separately into the picture tube of the TV, bypassing its comb-filter. The S-video or the composite video are supposed to be no match to the component video, and the scientific basis for assuming so is really solid. It has become difficult for TV companies in India to sell TVs, particularly the large screened ones, without component video inputs. Like many, I too was keen on buying a TV with component video inputs. After all, my DVD player (Philips DV-625K) had component video outputs, and I wanted to make full use of them. So I ended up buying a Philips Eye-Fi, 29" TV with component video inputs. The TV also had the S-video & composite video inputs. The combination of the two was perfect. The picture was beautiful and the sound was good when component video was used.
Recently, when I switched over from the Philips DV-625K to a Pioneer-676A, something went seriously wrong. Using the component outputs of the Pioneer, I was not getting proper colour balance on my Philips TV. Blue was missing, and there is a reddish hue to the picture. Changing over to composite video corrected the colour imbalance, but at great cost of the resolution. I was troubled, and got the component video circuits of my TV and DVD player checked, only to find out that both are in good working condition. I was at my wits end!
Finally, as a climb-down, I obtained a quality S-video cable (which turned out to be costlier than my gold-plated component video cables), and connected the Pioneer DVD player to my Philips TV. To my utter surprise, the quality of picture was at its best, even better than what I obtained earlier using the component video output of the Philips DV-625K. But this shouldn't be the case, isn't it? Is my subjective mind deceiving me? How can the S-video (Y-C) be superior to the component video (Pb-Pr-Y)? So I did some research, and gathered the following information, which reveals that with most of our TVs, component video is not necessarily the best option. Read on, and don't forget to respond.
(1) Component video comes in two flavors, interlaced (i-format) & progressive (p-format). Interlaced component video is what most of us have in our homes, in TVs as well as DVD players. Interlaced component video comes in different resolutions, 480i for NTSC at 60 Hz, 576i for PAL at 50 Hz (Standard Definition TV), and 1080i for interlaced HDTV. Similarly, progressive component video also comes in different resolution formats, 480p for NTSC at 60 Hz , 576i for PAL at 50 Hz (Standard Definition Progressive Scan TV), and 1080p for progressive scan HDTV. There is also an alternative progressive scan HDTV format called 720p, which requires the corresponding output from the DVD player. There are subtle differences amongst the different formats interms of Pb, Pr and Y. Thus it turns out that the component video output of your DVD player may, or may not be compatible with your TV's component video inputs. Very few TVs (read, only the most expensive ones) can decipher the incoming component video signal's format, and automatically switch over. If they are not compatible, then you will notice that the picture is worst using component video than the S-video. Even if they are compatible, component video cannot offer noticeably better picture than S-video if your TV employs only the standard 480i / 576i resolution format. You will notice the difference with the component video only if you have higher formats.
(2) In testing, it has been found that the component outputs of many DVD players do not conform to any of the four systems. They are not even consistently wrong enough to create a fifth, sixth or seventh category of component voltage levels. So it may so happen, that a company like Philips may evolve a unique component output format on its DVD players, which works best only with the Philips TVs. Many of the diplay differences can be corrected if the TV/ monitor has individual memory for gray scale, brightness, contrast and color for each of the component inputs. You will also need appropriate test signals from the DVD player, plus the skills and light measuring equipment needed to make the proper adjustments. Finding a TV/ monitor with all of the adjustments and the necessary memory for each input is an impossibility in Indian home environment.
(3) When the component video format arrived, it was something which the TV and video processor companies did not anticipate happening. While the TVs had S-video inputs & the S-video decoders which split S-video signal into Pb, Pr and Y before finally feeding it into the picture tube as R, G, and B, the chips had the Pb, Pr and Y component stage buried deep inside, where it can't be accessed directly from an outside Y, Pb, Pr input socket (bypassing the S-video decoder). But in order to sell TV sets in the DVD age, component inputs must be provided. Therefore, it is often accomplished by most TV-manufacturers by down-converting the incoming component video signal to S-Video, then sending that signal to their standard decoder chip to again split it into R, G, B. Consequently, there is a picture quality loss going from component to S-Video. On the other hand when you use S-video inputs, this stage is eliminated. This is largely responsible for many consumers reporting that they get a better picture from the S-Video input than they do from the component input.
