Module 47
Updated: 07/09/2006
Module 47
Updated: 07/09/2006
Film has retained its basic formats for more than 100 years. But, in the last few decades, videotape has progressed through no less than 20 different (and incompatible) formats.
Although this may be one of the prices we have to pay for progress, it has also added a bit of confusion to video production.
In this discussion we'll skip over most of the video formats that have been introduced over the years ---most of them didn't stay around too long anyway -- and very briefly look at the most recent and widely used.
In this module we'll focus on consumer videotape equipment. In the next module we'll cover professional equipment -- although, in recent years the dividing line between these categories has gotten a bit blurred. Serious hobbyists often select professional equipment, and consumer equipment often finds its way into professional applications.
Before we start our discussion of consumer formats we need to go into something that is basic to all of them: data or digital compression.
All consumer and most professional video formats use some level of video compression. They are often divided into lossless
and lossy,
although there is no clear line between the two categories.
With lossless compression there is no difference -- or some people would say, no readily discernible difference -- between the original and the compressed data. Thus, no loss in quality.
The problem, however, is that lossless techniques are technically quite demanding. Thus, they require expensive equipment.
Most video and audio compression techniques eliminate data to some degree to make recording and transmission technically easier to achieve. It then becomes a matter of how much
the data is compressed. When to the trained eye quality starts to be sacrificed, the term lossy compression is used.
If you start out with 100 bits of data and compress it to 50 bits, you have a 2:1 compression ratio. If you can reduce the original data to 25 bits, you now have a 4:1 compression ratio. Often, compression ratios aren't in nice even numbers, but in decimals, as for example, 2.5:1.
You can easily use a 2:1 compression with video without noticing any loss in quality. In fact, you can even compress video to 10:1 without noticing a significant difference -- and, in the process, of course, you can record the data in 1/10 the space. When you move to 20:1 (and depending on the subject matter), you will still have an excellent picture; however, the trained eye will notice a slight loss in quality.
Note in the windows and in the face in the photo on the right below the pattern added by compression. Compare that with the photo on the left that has minimal compression. We'll look at another type of compression later.
As you move to 50:1 and beyond, you can begin to see a noticeable (and objectionable) difference between the original picture and the compressed version.
This difference is much more noticeable in the 300% enlargements in the two photos on the left below.
In full motion compressed video, you often see little blocks or squares appearing in the video, especially during rapid action involving large areas of the picture. Note photo on the right above.
At the same time, in video you aren't sitting still studying still images; subject movement and the sequence of images involved tend to make imperfections less noticeable.
There are various digital compression approaches for audio and video. Any specific one, such as MPEG-4, which we'll discuss in a moment, is referred to as a codec. (Another one of those terms you can toss around to impress your friends!)
Top-of-the-line digital camcorders use a "no compromise" digital 4:2:2 format. Although somewhat technical, we often see video compression described in these terms, and so it may be advantageous to know that they mean.
The first number refers to the luminance or black and white part of the video and is an expression of the component-sampling ratio (not the compression ratio). The second two numbers refer to the sampling ratio of the color components of the video signal.
If that seems a bit incomprehensible, just keep in mind that 4:4:4 is a pure, uncompromised signal; 4:2:2 represents minimal and unnoticed compression; and 4:1:1, which is associated with DV camcorders, involves significant signal compression-and no, you won't be asked to explain the details of these things on a test!
MPEG-2 and
MPEG-4 are popular and sophisticated compression techniques that eliminate redundant
video information. This is data between successive frames that does not change, as well as data "that we won't miss" within each picture.
However, rapidly changing subject matter such as a hockey game is particularly taxing for a compression scheme. In this case the discarded data may be necessary to reproduce all of the detail in the action. It is in this type of subject matter that you are most apt to see artifacts , visible problems caused by the compression scheme not keeping up with the speed of action.
Most consumer camcorders use a 4:1:1 format (such as DV, DVCAM, DVCPRO, etc.), which depend on a greater level of quality-sacrificing compression. But even at this level of compression, most people will not notice the loss in quality.
Plus, there can be two other problems.
Since MPEG compressed video relies on data in adjacent frames, if the video is stopped on a particular frame — as would be the case in editing — critical data will be missing.
Finally, because MPEG data must be stored for brief moments in order for the system to evaluate a sequence of frames, there's a slight delay in processing the video. This can befuddle video editing equipment.
It's possible to process MPEG-2 video so it will work in a limited way in editing systems; however, such things as fades, crawls, and wipe effects are
a problem.
To get around some (but not all) of the problems with MPEG-2 compression an even more sophisticated type of compression, MPEG-4, arrived on the scene in the early years of 2000.
MPEG-2, which by then was more than 10 years old, had a
problem keeping up with the high data rates associated with HD or HDTV video.
With the arrival of HDTV, MPEG-4 entered the picture (no pun intended). Satellite transmissions, including the DISH Network HDTV channels, were among
the first to use MPEG-4.
Even though higher compression ratios are possible with the MPEG codec, because of its editing limitations, editors much prefer JPEG compression where each video frame is complete and able to stand on its own. Among other things, this makes frame accurate editing possible.
Whereas MPEG can create compression ratios of 30:1 without appreciably degrading video quality, JPEG compression is normally about 15:1 -- although that can vary considerably, depending on the content of the picture.
JPEG compression uses a highly sophisticated mathematical approach to eliminating (to varying degrees) nonessential picture elements. It's also "scalable," meaning that you can easily choose from a range of compression ratios.
More specific information on some compression approaches is 
available here
.
As we've noted, data compression is necessary because today's equipment cannot easily handle the high-speed data steams associated with digital video.
However, as data storage becomes cheaper and more compact, and computer chips become faster, uncompressed audio and video may become the norm. A number of video professionals now see this development on the horizon.
Most people are familiar with the popular 8mm and VHS formats. But before these, there was the once-popular Betamax format that was introduced by Sony Corporation in 1976.
Although it eventually lost out in popularity to VHS, it was the first consumer format to be widely accepted for home use.
Betamax was finally discontinued in 2002.
The most successful of all the home videotape formats has been VHS (video home service).
Although the VHS format has lasted more than 20 years and has spawned hundreds of thousands of video rental stores around the world, things quickly 
started to change with the development of DVD.
Note from the graph on the right that in 2001 the sale of DVD hardware and software (movies) surpassed VHS.
There was a bit of a lag in the rental market, however. As we've noted, it wasn't until 2003 that DVD rentals surpassed those of VHS.
Even so, we'll probably have VHS tapes around as a video rental format for a while -- especially for G- and PG-rated films.
The exploded view of a VHS cassette on the right below shows the two internal reels and the tape path. This basic design is used for all cassettes.
Although the technical quality of VHS has been improved significantly since its introduction, when it comes to professional applications the quality still leaves a lot to be desired
-- especially if significant editing and video effects are needed.
Although you do occasionally see VHS on broadcast TV (America's Funniest Home Videos, etc.) you probably wouldn't want to see the same technical quality in your general TV programming.
VHS took a step forward in quality when S-VHS (super VHS) was introduced. Some news operations started using it as an acquisition format that could be brought back to the production facility and immediately dubbed (copied) to a higher quality format for editing.
This minimized any subsequent loss in quality due to editing. For a discussion of acquisition formats 
click here.
To reduce the size of camcorders, a smaller version of the VHS and S-VHS cassette was also
introduced. VHS-C and S-VHS-C ("C" for compact) are a fraction of the size of the standard VHS cassette. They were designed to compete with the small 8mm format (discussed 
below) that found favor with a large number of consumers.
The symbols for 8mm, Beta, VHS, Super VHS, and VHS Compact are shown at the left.
Using S-VHS equipment in news has some major advantages; specifically, the equipment is easier to operate than professional equipment, it's lighter in weight, and it's far less expensive.
Since a quality S-VHS camcorder is "only" about $1,000 and professional equipment is at least ten times that amount, it's to some degree "expendable."
This is significant in covering news in third-world countries where some political regimes have a habit of confiscating reporters' tapes and equipment in an attempt to censor things they don't want the rest of the world didn't know about.
Like all of the videotape formats, VHS tapes have a record lockout
provision. Once you break off the small plastic tab shown here, machines will no longer record on the tape. This makes it possible to keep important material from being accidentally erased.
8mmWhen Betamax (not to be confused with Betacam
, to be discussed in the next module) didn't survive, 8mm video was introduced.
The format in part tried to cash in on the "8mm" designation that had long been a household name in home (film) movies. In fact, Eastman Kodak was one of the originators of 8mm video.
The reduced size of the 8mm cassette meant that camcorders could be made even smaller than VHS camcorders, a feature that attracted people who had grown weary of dragging around their bulky, full-sized VHS camcorders .
At about the time that S-VHS was introduced, Sony introduced Hi8, a higher quality version of 8mm. This is also used as an acquisition format, and under optimum conditions can produce high quality video.
In mid-1999, Sony introduced Digital-8 for the consumer market. This format not only represented a major improvement in quality, but the digital approach made new camcorder features possible.
Digital video recording has a number of advantages over analog. Although we've mentioned some of these in previous modules, we'll summarize
five major advantages here.
At the same time, compared to analog recording, digital recording requires far greater amounts of data.
This drawing illustrates the ten sequential tape areas (and 10 head rotations) that are typically necessary to record just one video frame. The red and blue areas show the video and audio data regions.
Digital formats are also becoming widely used as acquisition formats -- with impressive results.
DV CamcordersMany consumer digital camcorders use DV videocassettes, which are even smaller than a standard audiocassette.
One camcorder model is so small it can fit into a shirt pocket. (Note photo here.)
Many of these units now have a FireWire connection, a high-speed data connection that allows the output of the camera to be fed directly into a computer or digital editor.
...tape in camcorders will eventually die away, just as it has in other recording devices.
David Pogue, The New York Times
There have been dozens of approaches to recording dozens of different audio and video signal configurations. However, in the amateur, prosumer, and professional areas, all recording formats seem to be moving to recording and playing back the same type of MPEG and JPEG compressed data. It's only the way of storing and playing it back that differs.
Atapeless camcorder was introduced by Hitachi in late 1997. The MPEG Cam could record up to 20 minutes of video and audio on a detachable 260 MB hard disk.
In early 2005, JVC introduced two disk-based camcorders that represented a major step forward. These cameras record up to one hour of video on removable, four-megabyte MicroDrives. The cameras can also record on Compact Flash and SD memory cards
These camcorders (shown on the right) are small enough to fit in a shirt pocket and come with a USB. computer cable for uploading the scenes into a computer for editing. Computer editing and DVD-burning (creating) software comes with the cameras.
In the next module we'll discuss the latest technology for professional video recording: blue laser optical and solid-state SD memory-based camcorders. However, before we end this module there are a few loose ends in recording media we need to mention.
In 1999, a technology was introduced for recording TV programming in the home that has a number of important advantages over VHS videotapes. PVR, or personal video recorders, use a high capacity computer hard disk to record 100 or more hours of programming.
The units make it possible to do instant replays of material and to speed through commercials at up to 300-times the normal speed. (As commercials in one form or another are now approaching 50% of prime-time programming content, many people feel that this feature alone makes the investment worthwhile.)
As the cost of hard disk storage continues to drop, we will undoubtedly see the audio and videotape media relegated to the history section of the Museum of Broadcasting -- and you will be able to tell your children or grandchildren, "I remember back when they used to record audio and video on a piece of moving tape!"
It was not too long ago that a broadcast quality camcorder was $60,000. Today, digital camcorders that can be used in broadcast applications cost a fraction of that. This has led to what some have called the "democratization of the medium."
With the proliferation of public access opportunities on cable channels and Internet video, the ideas and concerns of many more people can be expressed and heard.
Seeing something is quite different from reading about it. Although an event may take place that can and should elicit a public outcry of opposition, until it is recorded on video for "all the world to see," little may be done. Such is the power of the video medium.
Compared to film, digital video has its own unique characteristics. It can look sharper and colder than film, and exhibit compression artifacts that many people feel detract from the video medium.
At the same time, for those who feel these things are not desirable, there are a variety of filters available that can counteract these effects. These are discussed here
.
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