- About Archives
- About SAA
- Careers
- Education
- Publications
- Advocacy
- Membership
John Walco, Scenesavers
Archivists are always faced with challenges regarding their collections. Perhaps none of these challenges are more intimidating than what to do with new types of materials as they arrive, especially when those new materials include new and never before seen formats. High definition television is no different. All sorts of questions come to mind, such as:
In order to know what high definition means to the archivist, it helps to have an understanding of analog television and where we have come from.
In analog television, there are three basic formats: NTSC, PAL and Secam. As you are probably aware, different countries around the world have selected different formats for their analog broadcasts, and one is not compatible with the other. In other words, you can not view a PAL videotape on an NTSC videotape deck or television, unless your equipment has been designed to play multiple formats.
NTSC television currently displays about 480 scan lines and the video image is "interlaced," meaning that all the odd scan lines are "painted" onto the screen and then all of the even scan lines are painted onto the screen. This "odd-even" method of creating the video image is one reason why straight lines can look jagged, especially when the camera pans across the field of view; for example, look at the edge of stadium seats the next time you are watching a sporting event.
High-definition television or HDTV is actually a sub-set of digital television, or DTV. While HDTV seems to get most of the press due to the potential picture quality and sharpness, when we talk about HD, we are really discussing digital television. Digital television is actually a set of voluntary standards created by the Advanced Television Standard Committee (ATSC) that consists of about 18 different broadcast formats (and you thought things were going to get easier as we moved toward HD). Of these 18 new formats, 6 of them include high definition formats. Keep in mind that both DTV and HDTV are broadcast standards and not necessarily videotape standards. This means that a lot of the information available about these formats pertains to broadcasting content, including the deadlines for when analog broadcast will be discontinued (Feb 17, 2009). But this also means that organizations that are creating content for broadcast may be creating it on an HD format. It is likely that this original content will end up in your archive at some point in the future.
As mentioned, current NTSC analog television is interlaced and consists of about 480 scan lines. It also displays the picture in a 4x3 aspect ratio (meaning the image is 4 units wide for every 3 units high). When the original analog broadcast standards were created, this made sense because most of the motion picture film shot pre-1950s was in an aspect ratio that was close to 4x3.
With HD, there are three specific areas that have improved picture quality, including aspect ratio, noise and lines of resolution. For example, the image displayed is 16x9 instead of 4x3, meaning that the field of vision is more like a movie screen. It is also closer to your normal field of vision, and appears more like we see the world. This is important where a wide field of view can offer a benefit, such as a sporting event where you get to see more of the field.
With the older analog broadcast, noise affected the signal and typically the further you were from the broadcaster, the worse the noise became. The image would eventually fade until you could no longer receive a signal. With digital and HDTV, the data is literally made up of ones and zeros meaning that the image quality stays constant until you hit the edge of the broadcast range, where the image suddenly drops off (this actually means that either you have a signal or you don't; there is no in-between). Also, being digital means that you can clone a tape and make new copies with little or no perceived loss in quality. This is not true for analog copies where each copy incurs "generational loss," meaning that each successive copy is slightly worse than the original.
The third area is scan lines. Current analog television goes up to 704 (horizontal) x 480 (vertical) scan lines. High-definition television can go as high as 1920 (horizontal) x 1080 (vertical) scan lines. This additional information included in the picture results in an image that is much sharper and clearer. In addition to increased scan lines, there are also differences in the way the image is created during playback. As mentioned, current analog television is interlaced. HD can either be interlaced or progressive scan. Progressive scan means that the scan lines are created in order, just like a computer monitor, and results in a very sharp image. When discussing HD, the type of image and the way the picture is created is typically written as number of scan lines followed by either an "I" or a "P". For example, 1080i means 1080 scan lines, interlaced; 720p means 720 scan lines, progressive.
Digital broadcasting also adds considerably more audio capabilities than analog television. 5.1 dolby digital surround sound, means there are 6 channels of audio, compared to two with current analog broadcasting.
DTV and HDTV are really broadcast television formats, so why does an archivist need to be concerned about them? Like anything technology related, television is constantly changing. New formats are emerging and older ones are being replaced. As your organization moves in these new directions, these formats are going to start showing up in your archive and you'll need to be able to identify them and know what to do when they arrive.
Part of the problem is that the preservation of videotapes is going to get more complex and challenging. Not only are you going to have new formats to contend with, they are going to require special equipment just to view them. And not all the formats are compatible with all others. For example, Sony has both a 1080i and 1080p as well as a 24p format (which is 1080p, but shot at 24 frames per second, not 30 frames per second, like standard video). These formats are not compatible and a tape recorded in one format will not play in a tape deck designed for another format.
For the time being, it may be sufficient to place these videotapes on a shelf, but at some point, the content will need to be migrated. You'll need to be able to identify what formats you have to ensure they can be transferred in the future.
It is difficult to say how long these formats will last. The videotape formats utilize a metal formulation in their tapes (either metal evaporated or metal particle tapes), which tends to be fairly robust. Studies done by manufacturers demonstrate that these tapes should have an effective useful life of up to 30 years, assuming good storage conditions, single use tape. Some of the HD footage is being recorded directly onto optical disks. Manufacturers tell us that they expect optical disks to last longer, but the disks haven't been around long enough to make an accurate determination. As always, multiple copies on multiple formats in multiple locations is a prudent course of action.
The question often comes up of what to do with existing analog formats. Should these be transferred to high definition now, or when transferring for preservation? The best answer at this point is that standard definition formats should remain standard definition. There are many reasons why, but the main one is because there is no best standard for high definition. Each broadcaster has chosen a format that best suits their needs, meaning there is no sure way to know the format you choose today is the format they will want tomorrow. If your material will be used again for editing or for broadcast, the user can convert it to the format of their choice when necessary.
You might ask "What if I already have an HD format and need to transfer it... what should I do?" Although new formats are emerging, they are years away from being available. The best and highest resolution HD format that is available today is 1080p (1920x1080 progressive scan). If you need to make a choice and need to transfer to a HD format that will have a high likelihood of being compatible with all possible future use, you should attempt to transfer existing videos 1080p. However, this course of action should only be followed when absolutely necessary and if no other options are available. (720p runs at a speed of 60 fps, vs. 24 or 30 fps for 1080p. This may mean 720p is a better choice for content with a lot of fast motion). Another consideration is the quality of 'upconversion', which is the process of scaling a standard definition video signal up to a HDTV signal. This process continues to improve. It may be better to wait on upconverting existing content, allowing the process to continue to improve.