Updated:  02/10/2017

 

 

Digital

Broadcasting

Part II

 

The World Moves to DTV

By 2014, the majority of countries in the world had switched from analog to digital broadcasting.

Digital TV has numerous advantages. For one thing, it uses a more efficient transmission technology allowing for improved picture and sound quality.

In addition, through the use of multiple digital subchannels (channels of information within the basic broadcast signal) digital signals provide more programming options.

Compared to analog signals, digital broadcast signals react differently to interference.

Common problems with over-the-air analog television include ghosting of images (seeing multiple faint images at the same time; note photo), noise or "snow" because of a weak signal, etc.

Degraded analog signal reception result from factors such as a poor or misdirected antenna and changing weather conditions.

But even under these conditions an analog signal may still be viewable and you may still hear the sound.

Digital television transmissions are more demanding. The nature of digital TV results in a perfect picture initially, or until the receiving equipment starts picking up interference or the signal is too weak to decode.

With poor reception some digital receivers will show a  "blocky" video or a garbled picture with significant damage, other digital receivers will go directly from a perfect picture to no picture at all. This phenomenon is known as the digital cliff effect.

The first country to make a complete switch to digital over-the-air (terrestrial) broadcasting was Luxembourg, in 2006. Shortly thereafter, the Netherlands made the switch. Finland, Andorra, Sweden and Switzerland followed in 2007.

In June 2009, major broadcast stations in the United States switched to DTV.  We say "major" because some lower power TV stations were allowed to stay with the NTSC analog standard for some time.

Some countries don't plan a complete analog-to-digital transition until around 2020.

As shown in the illustration below there are four basic international standards for digital broadcasting..

You will note that the United States and Canada use the ATSC (Advanced Television Systems Committee) standard.

World Digital Standards
 

These incompatibilities are important to keep in mind with dealing in international programming.*

One of the major differences between analog and digital TV is the number of horizontal scanning lines that typically make up the picture. The greater number of lines the more picture detail is possible. The table below summarizes these differences.

Standards
SDTV (Analog)
HDTV (Digital)
Total Lines 525 1125
Active Lines 480-486 (maximum visible on the screen) 1080 (maximum visible on the screen)
Sound Two channels (stereo) 5.1 channels (surround sound)
Max Resolution 720 X 486 1920 X 1080


As you can see, the ATSC broadcast standard is capable of 16:9 images up to 1920 by 1080 pixels, which is more than six times the display resolution of the older (SDTV) analog standard.

With digital TV the resolution can even be much greater, as you can see in the comparisons below.

  •  Standard definition -- 480i (interlaced) that are compatible with existing NTSC sets

  •  Enhanced definition -- 480p, (progressive), about the same quality as current DVDs

  •  High-definition -- 720p

  •  High-definition -- 1080i (the highest definition currently being broadcast)

  •  High-definition -- 1080p (Blu-ray equipment and a few cable operators)

  • Ultra HD, 4K UHD has a resolution of 3840 pixels × 2160 lines, or 8.3 megapixel bandwidth and an aspect ratio 16:9

  •  And finally, there is 8K UHD which is 7680 pixels × 4320 lines, or 33.2 megapixels with a 16:9 aspect ratio

4K UHD and 8K UHD have been developed primarily for use in specialized applications such as medical TV, and there is some question whether such ultra-high resolutions with their high technical demands are practical for the home viewing market.

However, the difference between SDTV and  HDTV is a different matter, as you can see from the illustrations below'

Differences in SDTV-HDTV Detail

The screen enlargements shown here represent HDTV (on the left) and the standard NTSC systems (on the right).

When projected on a 16 x 9-foot screen and observed from normal viewing distance the picture detail in good (1,080p) HDTV systems appears to equal or better that attained by projected 35mm motion picture film.  

The best video projectors can reproduce detail that is significantly beyond what's possible with the standard 35mm motion picture projectors used in theaters.

Whereas SDTV produces an image with about 200,000 pixel (picture) points, HDTV increases that by a factor of about 10 to two million pixels. 

The relative detail density, which are represented here, assume a 40-inch TV screen at normal viewing distances. 

 

As more and more theaters switch to video projection, the use of film is being phased out.

According the National Assn. of Theatre Owners' trade group by 2012 more than 85% of the U.S.'s 4,044 theaters, representing 34,161 screens, had gone digital. We'll have more on digital cinema later in this module.


Comparisons between video and film quality are subject to lively debate.

Most of the earlier weaknesses of video, such as loss highlight and shadow detail, have been overcome with the newest professional video cameras. 

Even so, many producers (and especially many actors) prefer the slightly softer look of film.
 

Converting Wide-Screen Formats

Production facilities make the conversion of 16:9 HDTV/DTV images to the standard 4:3 aspect ratio in the same way they convert wide-screen films to SDTV. (We'll cover in-set conversion approaches later.)

Three approaches are used:

First, is when the conversion involves cutting off the sides of 16:9 image to a narrower 4:3 size. We refer to this as an edge crop or 4:3 center cut.

If we shoot the original HDTV with the narrower 4:3 cutoff area in mind, losing the information at the sides of the full 16:9 raster may not be an issue. (This is the area on each side of the red box in the photo below.)  

We refer to the procedure of keeping essential subject matter out of the cutoff areas as shoot-and-protect.

Second, the entire production can go through a process called pan-and-scan.

In this case a technician reviews every scene and programs a computer-controlled imaging device to electronically pan the 4:3 window back and forth over the larger, wide-screen format. The red arrows in the above illustration suggest this panning movement.

In the above picture, cutting off the sides would not be an issue; but what if important information was at both the sides of a frame?

If the full HDTV/DTV frame contains important visual information (as in the case of written material extending to the edges of the screen), panning-and-scanning will not work.

In this case, a letterbox approach can be used, as shown here.

But this results in blank areas at the top and bottom of the frame.

Often, with this conversion the letterbox approach is used for the opening titles and closing credits, and switch pan-and-scan for the remainder.

However, some directors feel that pan-and-scan introduces pans that are artificial and not motivated by the action or the scene composition they originally intended. They may insist that their work be displayed using letterbox conversion.

There is another way of handling the 16:9 to 4:3 broadcast conversion, especially for titles and credits. You've probably seen the opening or closing of a film on television horizontally "squeezed" in. We refer to this optical technique as anamorphic conversion.

The effect is especially noticeable when people are part of the scene -- people who, as a result, suddenly become rather thin. (Not that all actors would complain!)

Compare the two images above. Note how the parrot in the squeezed 4:3 ratio on the right seems to be thinner than the one on the left.

Another way of visualizing the major SDTV-to-HDTV and HDTV-to-SDTV conversion approaches is illustrated - here.

Clearly, all these approaches leave something to be desired, so today savvy producers originate productions in the 16:9 wide-screen format using the "shoot-and-protect" approach we've discussed.
 

Digital Cinema Development

In November 2000, moviegoers saw the film Bounce in both film and high-definition video.

Satellite facilities distributed the video version to digitally equipped theaters, which used high-definition video projectors. The difference between the film and video versions was difficult for audiences to discern.

Since 2000, there have been major improvements in the video projection process. By 2007, the images from the best video projectors were sharper than those of 35mm film projectors.

Clone Attack Movie"Film" crews shot Star Wars: Attack of the Clones, which more than 90 theaters around the world projected in digital form, entirely in 24p video, which we covered earlier.

Whereas film and processing would have cost several million dollars, the cost of videotape for this production was only about $15,000.

" More and more "films" intended for theaters are being shot with high-definition video.

After elements such as special effects, editing, and color correction are completed, a technician can convert the final product to 35mm motion picture film (if needed), or more commonly record the final result on a hard disk for distribution to theaters. "

3-D Video Production

Another major step toward video projection in theaters was taken with the release of the 3-D motion picture, Beowulf. This production also represented a major step in digital animation.

Beowulf is based on a famous Old English epic poem about a warrior who fights terrorizing monsters -- designed to be all the more scary in 3-D.

Despite the limited number of theaters equipped with 3-D video projectors and the fact that patrons had to wear special glasses, this film toped the box office when it was released in late 2007.

Another box office record was set in late 2009 and early 2010, by the 3-D film Avatar. Many theaters used video projectors for this production.

More On Cost Savings

Each year, the motion picture industry spends almost a billion dollars duplicating films and distributing them to theaters around the U.S. and the world.

Films have limited life; they collect dirt and scratches and soon must be replaced.

As we've seen, video can cut the billion-dollar figure to a fraction of this amount. yellow dot This file on digital cinema has more information.

Pirating (creating and selling illegal copies) costs the motion picture industry billions of dollars in lost revenue.

Pirating feature films is far more difficult when they're encrypted and either sent directly to theaters via satellite, or, more commonly, delivered to theaters on a high-capacity disk drives. We discuss the issue of pirating in more detail - here.

In addition to cost savings, digital cinema offers production advantages.

We can immediately play back and evaluate a scene shot in video -- even while the actors and production personnel are still in position.

With film the hours of delay (at least) are involved in processing and preparing film "rushes" (rough prints for quick screening) make this impossible.

Today, however, most film directors use video assist when shooting on film to check on scenes as they are shot.  They can then transfer the results to film, if needed.

Finally, not only are postproduction costs far less with video, but visual effects are much easier and inexpensively produced.

>>The chart below indicates the excepted growth of theaters moving to some form of digital "film" projection.

Percentage of U.S. Digital Theaters
2005
blue  (3%))
20062006
blue
2007
blue
2008
blue
2009
blue
2010
blue
2012
blue  (85%)

Today, most audiences can't tell the difference between the look of professional film and video projection systems.

The key differences between film and video are – discussed here.

 

 Traditional "Hollywood thinking" has long opposed production with video equipment for "serious, professional work." 

However, today, the cost savings for video production, not to mention video's many production, post-production and distribution advantages, make the move to video for both production and theater presentation inevitable.

 

Other Advantages of Video

In addition to showing feature films, theaters with digital projectors can provide patrons with other entertainment, such as live concerts, Broadway shows, sporting events and productions aimed at special audiences.

Digital theaters can operate with fewer employees, which represents a labor cost savings.

Offsetting this savings, however, is the initial investment for digital projectors and the associated computer -- an estimated $60,000 to $120,000 per theater screen.
 

Are 3-D TV Productions

Finally Going to Catch On?

Over the years, three-dimensional (3-D) TV programs have often tried, and failed, to catch on with the general public.

That seemed to be changing in 2012, when many TV sets were equipped to display 3-D images.

However, it turned out to be another false start. By 2014 it was apparent that there was not wide acceptance with the general public and the largest TV set manufacturer, stopped making 3-D sets.

As we've noted, theaters had better luck.

Avatar, which most people saw in 3-D, gave 3-D a major boost in theaters.

In 2015, Star Wars: The Force Awakens broke all previous box office records the first weekend after its release.  Ticket sales exceeded one-half billion dollars in North America alone.

By 2016, motion pictures were being routinely released in 2-D and 3-D versions.

In the next module, we'll begin discussing audio and video equipment, starting with a key part of a video camera: the lens.


*More in-depth technical explanations of the various television systems can be found at Wikipedia.



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