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Standard Definition Sources

Because it is an analog signal, NTSC video can be a bit confusing when we speak in terms of total resolution. We already know that Standard definition television is 480 lines of vertical resolution, however that only describes the total amount horizontal lines of resolution, not the amount of vertical lines of resolution that are referred to as the horizontal resolution. (Remember: NTSC video is an interlaced image, meaning that only 240 vertical lines of resolution shown at any given time).

Because Standard definition is an analog signal, horizontal resolution doesn't have to be finite like in a digital signal. In other words, there isn't a grid line on your television marking exactly where the horizontal resolution has to be. Instead, we measure the maximum number of transitions — from dark to white — that a signal can resolve over a given width. Complicated, right? To make things easier, we will do the math for you and represent the total maximum horizontal resolution. *It is important to note that when we talk about horizontal resolution, we will always assume a 4:3 aspect ratio because NTSC video is always in a 4:3 aspect ratio.

Because a standard definition signal is 1.33 times wider than it is tall, it might seem odd that the horizontal resolution is often actually lower than the vertical resolution. This is because the human eye is better equipped to resolve vertical resolution than it is horizontal resolution. Early engineers understood this and as a result kept this signal as small as possible.

Let's move on to the different types of video sources.

Video Cassette Recorder

The good ol' VCR; it certainly seems to be on its way out. But did you know that there are two different types of analog VCR's in existence, and with regard to resolution, they display different overall images. Let's take a look at both.

1. The standard VCR is an analog tape device that displays NTSC video so it has a vertical resolution of 480 lines. Its maximum total horizontal resolution is approximately 320 lines, and that resolution would be achieved when using the slowest speed setting. 320 lines is, by far, the lowest resolution out there. Added to the low resolution number is the fact that analog tape degrades with usage so it's no surprise that people are rushing out to buy DVRs (digital video recorders) and recordable DVDs.
2. The upgrade to the standard VCR is the S-Video VCR, which will suffer from degradation as well, but ups the maximum total horizontal resolution to approximately 560 lines.

Over The Air Broadcasts

Standard definition television from an antenna has the usual 480 lines of vertical resolution and a maximum total horizontal resolution of 440 lines. The main problem is that this is an over-the-air signal and reception is iffy. Unless you are in the line-of-sight of the transmitting tower, overall picture quality will suffer. Additionally, weather and other numerous factors can have dramatic effects on reception.

Cable Television

This section is about cable television and how it applies to NTSC video, not HDTV.

Cable television is probably the single most misunderstood video source out there because cable and can be comprised of both analog and digital signals. For cable, all channels below 100 are sent to your house in the form of analog signals. These signals — and those of the digital variety — are in the same resolution as broadcast, or over-the-air, signals. The difference in clarity between channels under 100 and channels over 100 — which are all digital, is due solely to the differences in receiving analog and digital signals.

Because the channels above 100 are converted to digital signals before they are transmitted to your home, they are practically immune to interference along the way, resulting in clear, crisp images. Conversely, analog channels travel a long way to get to your home and over that distance they encounter a variety of interfering factors, resulting in degraded images.

You might ask, why not transmit all channels digitally since the technology to do so obviously exists? The answer is quite simple: most televisions are "cable ready," meaning that they have a built-in cable tuner that is able to read an incoming signal. This is why you no longer need an external cable box to receive standard cable channels.

If broadcasters were to digitally convert their entire inventory of channels prior to sending them out, everyone - with the exception of a few people who have the latest digital cable-ready televisions - would have to use an external cable box to watch cable. Renting the box is an additional cost and an inconvenience that most people simply don't want.

Digital and Analog Satellite

Satellite television comes in two forms: the newer, smaller digital satellite receivers and the older, larger analog receivers that are still used in rural locations across America. The analog receivers have the same resolution as broadcast television, as well as cable, and will also suffer from interference just like over-the-air and cable analog systems.

Digital systems convert all channels to a digital format before transmitting them to a satellite and down to your home, effectively avoiding the interference that plagues analog systems. One of the quirks suffered by digital systems is if a signal is sufficiently weak, the signal can't be displayed at all. This means that a digital satellite dish needs to be placed in the line-of-site of the satellite itself in order to receive the signal, thus limiting availability in certain areas.

DVD

The first fact we need to understand about DVD is that it is a digital source. The second is that DVD is currently not HDTV. It displays the same NTSC signal that we've been talking about, although there are some major caveats.

Although a DVD is a digital storage medium, the players generally convert signals to analog before sending them to your television. The resolution of DVD is the normal 480 lines of vertical resolution and the maximum total horizontal resolution is set at 720 lines. For standard definition television it doesn't get any better than this.

If you are the technical-type and you already understand that a DVD stores information digitally, you probably have a rather interesting question by now. Because DVD is digital, it must store the resolution as pixels instead of scan lines. This means that you should be able to divide the horizontal resolution by the vertical resolution and get the aspect ratio. However, 720/480 yields a 1.5:1 ratio. So what gives?

DVD pixels aren't square. DVD resolution is made for 4:3 standard televisions, but with an eye to the future. We will cover much more on this subject in the section "Anamorphic and Progressive Scan DVD's Explained" in our advanced section.

Camcorders

Camcorder resolutions vary depending on what the recording medium is. They all will have 480 lines of vertical resolution, but the maximum total resolution varies.

1. VHS based — This is an older analog technology but it's still out there. Its maximum total horizontal resolution is approximately 320 lines.
2. S-VHS and Hi-8 — Again, this is an older analog technology, but it's much more common than VHS-based camcorders. Their maximum total horizontal resolution is approximately 560 lines.
3. Digital Camcorders — Includes all types of formats. Their maximum total horizontal resolution ranges from 650 - 720 lines.

High Definition Sources

Obviously all HDTV sources are going to look great. It's the nature of the technology. Here is a bit about each.

Over-The-Air Broadcasts

Setting up an antenna and receiving HDTV is simple, but your results will vary. First, because HDTV is digital, you will either receive a signal and an image, or you won't. Being close to a major metropolitan area is a must. If you are able to receive an image, the only other thing that can keep you from receiving a perfect image is the strength of the signal. HDTV receivers use something called "error correction" to fill in information gaps in a signal that fades in and out. If the signal is too degraded, the image can "digitize," when an area of the image, or the entire image, looks like it is made up of enormous pixels or single blocks of color, or freezes, making the image unwatchable.

There are various HDTV receivers/tuners that will decode HDTV digital signals to display on your HDTV television. All HDTV receivers/tuners will accept either HDTV format (720p or 1080i), and before sending a signal to your television, they will convert the signal to either 720p or 1080i. However, some will only output 1080i signals, while others only output 720p, so use care when selecting your receiver/tuner. If you want to spend extra for added flexibility, high-end models will keep a signal in its native format and pass it on to your display.

To build on this, here is a list of HDTV stations and their over-the-air HDTV formats:

720p - ESPN, ABC, Fox
1080i - NBC, CBS, PBS, HBO, Showtime, HDNet, Discovery HD

HDTV via cable is more stable than over-the-air broadcasts and will also give you more choices for HDTV content like HBO, The Discovery Channel, etc. Cable television compresses the signal — or converts the data into a smaller signal while maintaining most, but not all, of the quality of the original signal — before sending it to your television. Because there are different forms of video compression, it is hard to quantify the exact resolution that is lost, but for the most part, it is negligible to the viewer.

Digitized images and image freezing can still occur with cable television if there are transmission problems, but these incidents seem to occur less often now that HDTV has become more common.

Cable providers tend to distribute newer HDTV boxes with convertible outputs for either 720p or 1080i formats to better meet your needs. There are still older systems in circulation that can only output one format or the other and are only equipped with component-type outputs, unlike newer systems furnished with both component and DVI outputs. We will explore this further, as well as cables and signals, in the next section.

Digital Satellite

Digital satellite systems offer a variety of HDTV channels, much like cable, with one drawback: they usually don't offer local HDTV stations. Because a digital satellite system is a line-of-sight system, it can be prone to outside interference and will exhibit the same problems as over-the-air signals. Satellite systems also tend to use more compression in HDTV signals than cable systems, which sometimes yields noticeable degradation of overall image quality. Results can vary from system to system and from day to day.

Digital Video Cassette Recorder

JVC came out with what is known as the D-VHS recorder some time ago, however the technology is not as popular as was originally anticipated.

Such is the case with any digital recording, D-VHS playback is normally flawless, but degradation of the tape as well as the recorder's head often occurs over time. And, because there are so many options in digital recoding today, problems with this particular medium will most likely keep the technology from growing in the U.S.

DVD

High Definition DVD is now a fact and no longer a figment of the imagination. New blue laser technology provides DVD with a much greater storage capacity so it can now be used to record and playback full-length HDTV movies. Like standard DVD, there aren't really any major drawbacks to this system. It should deliver perfectly clean HD video for the life of the DVD without degradation of image quality or resolution. It should also be backward-capable, thereby allowing you to watch your "old fashioned" standard definition DVD's.

The only issue holding back DVD for now is that there are currently two different standards competing for dominance. We won't go into each of their merits, as we anticipate that the market will work itself out within the next couple of years.

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