High Definition Defined

Update: December 7th, 2009

High Definition Defined

by Ed McNichol

Back to Information Library

In this issue, I’ll talk about the key points that everybody, from producers and directors to the home consumer, should understand about High Definition television. Much of this information is critical in your efforts to ensure the long-term value of your projects.

First of all, what is the standard for High Definition? Simply put, there isn’t one – there are many. Here’s why – the FCC has mandated a transition to digital television (DTV) for broadcasters. This move requires either standard definition (SDTV) or high definition (HDTV) broadcasting. Standard definition is essentially a redefining of current television standards, but broadcast in a completely digital form.

Selected stations in the ten largest television markets must air DTV by November. The rest of the country is then rolled in over time, largest markets first. This timetable allows larger markets to bear the brunt of the R&D costs associated with this new technology. The conversion to DTV must be complete by May of 2006 when all stations will shut down the existing analog channels and return that spectrum to the FCC, thus retiring NTSC at the ripe age of 65. Here in Seattle, KOMO and KCTS have already begun digital broadcasting, with KING and KIRO starting shortly.

On the other hand, High definition has many forms and shapes. Basically, any scan line count above 480 (current specs) can be considered “High Definition”. The Advanced Television Systems Committee (ATSC) has formulated a “table” of formats accepted as digital television. The ATSC table is a transmission specification; not a tape acquisition or mastering format. It provides guidelines for how broadcasters will transmit a digital television signal. And the table specifies MPEG2 as the compression format for all signals. Since MPEG2 can reduce the quality of an image, it is imperative that the highest quality signal be fed into the transmission bit grinder.

Here’s the ATSC Table 3, as adopted:

Yikes – I found this table as helpful as an Egyptian road map of Dublin using Cyrillic characters! No wonder TV looks so horrible now – nobody can understand the techno-spew that these slide rule types put out. There’s no way that table can make sense to the average producer. So, I got out my decoder ring and came up with a version that humans might be able to comprehend:

Simplified ATSC Standards Chart

Vertical lines

Pixel Widths

i/P

Aspect Ratio

Frame rates* (Hz)

480

640

i

4:3

30

480

640

P

4:3

24, 30, 60

480

704

i

4:3

30

480

704

P

4:3

24, 30, 60

480

704

i

16:9

30

480

704

P

16:9

24, 30, 60

720

1280

P

16:9

24, 30, 60

1080

1920

i

16:9

30

1080

1920

P

16:9

24, 30

* = All frame rates also allow for “NTSC compatible” versions.

Ironically, the lowest quality format that is accepted under the new standard is the highest quality we know today, 640×480 interlaced. And the highest quality is a specification for which NO equipment is yet available, 1920×1080 progressive.

Know Your I’s and P’s

One of the really important things to understand about the table is the i/P column. This means “interlaced” (i) and “progressive” (P). Interlaced refers to the manner which current video equipment displays a picture. A video frame is made of two fields, each of which contains half the information. When viewed together in 1/30 of a second, this provides a complete frame of information.

Progressive scanning is the manner in which computer monitors display information. They read in data from the top of the screen to the bottom, displaying a full resolution field. So, a progressive signal is less likely to have motion artifacts than its interlaced equivalent with the same number of vertical lines.

While 720P might seem like it could be a fair work around for the short term, only ABC has expressed any interest in this as yet undeveloped format. And a web search for 720P turned up an Amtrak Schedule and flights to Lebanon, New Hampshire. I’m not placing any large wagers on 720P as a long-term mastering format.

On the other hand, many manufacturers are preparing products to produce in the full 1080i format. APS has chosen the Sony family of production tools for their entrance into the high definition playing field. These products are based on Sony’s’ success in the component digital realm and operate with the same power and flexibility as their standard definition kin. And with six times the data, and 20% more picture than current video, the end results are breathtaking.

Can’t I Just Convert to High Definition?

People often wonder how they can utilize their existing legacy archival footage in high definition productions. It is possible to upconvert (or “upres”) your current footage to HD. APS has selected the Snell & Wilcox HD5100 for its pristine processing and fantastic output. However, this upconverted footage will not have the same image quality as native HD material. Also, the aspect ratio difference must be resolved in this process so that everything does not get stretched out of shape.

The question then arises – why not just master in Digital Betacam and then upconvert to HD? While we can use production techniques and different processes to integrate standard definition footage into your show using the HD5100, this is not a process I would recommend for mastering. The aspect ratio change poses a real problem and there is still a great deal of detail missing from these shots. An entire show that has been upconverted can not compete with a completely native HD program. An upconverted master may be HD in an electrical sense, but the difference will be readily apparent to the viewer.

Where’s the Rub?

The real challenge of high definition really lies in exploring this new landscape we now have to work with. How do you frame and light for the wider aspect ratio? How much makeup is appropriate with the enhanced detail? How are titles positioned? How do I master in 16:9 High Def, yet end up with a full height 4:3 deliverable master for today’s standard definition? Can I still make an Avid cut from High Def. field footage?

We are currently resolving these issues for our HD projects already underway, and look forward to making these solutions available for our other high definition shows. It’s a tremendously exciting time to be involved in production!

Buying a Home Television?

If you purchase a digital television for your home, there is one key thing to consider. While all televisions will be capable of receiving any signal in the ATSC table, there is an important difference in how they display these signals. Some sets will take every type of signal and convert it to a standard definition display. This conversion will degrade the original signal and reduce the viewing experience. Other sets will display signals in their native High Definition format, enabling you to view absolutely stunning images in your home!

Conclusions

There is going to be a great deal of confusion as this country migrates towards DTV. It is imperative that efforts be made to better educate the public about what this transition involves. As production professionals, we need to ensure that we are delivering to our clients a future-proof imaging format, not a master that is mortally wounded and has greatly reduced shelf life. Clients need to be able to reproduce, repackage, and realize capital from shows 4 to 8 years downstream. By better understanding high definition television, you will be able to recommend production formats that offer the maximum performance and longevity the project deserves.

No comments yet.
You must be logged in to post a comment.
TOP