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“Crystal clear both Audio and Video”

by: Dario R. Abawag

On Nov. 5 2006 The National Telecommunications Commission (NTC), gives a memo to all TV Stations in the Philippines to fully  covert from analog to digital technology until or before Dec. 31, 2015.

Recently the ABS-CBN Broadcasting Corproration applied for the digital television-terrestrial service (DTT) license to the National Telecommunications Commission of the Philippines, they’re planning to set up a digital transmission as early as they can, in other hand they are already experimenting digital transmission on channel 51.

Part of ABS-CBN  plan is to spend an initial P500 million for a partial migration from analog to digital TV technology and initially distribute for free 400,000 set-top boxes in pilot DTT areas. A set-top boxes cost around P1,000.00

Other Television Network also expressed their interest to switch to digital platform, like Associated Broadcasting Company (ABC-5), they’re already testing digital transmission at channel 47. Lastly GMA network also planning to go for digital tv.

What is Digital TV?

Digital television (DTV) is the sending and receiving of moving images and sound by means of discrete (digital) signals, in contrast to the analog signals used by analog TV. Introduced in the late 1990s, this technology appealed to the television broadcasting business and consumer electronics industries as offering new financial opportunities.

Digital television is more flexible and efficient than analog television. When properly used by broadcasters, digital television allows higher-quality images and sound and more programming choices than analog does. However, although DTV allows for superior technical quality, a digital signal does not necessarily carry a higher-quality image or sound than an analog signal.

Advantages to conversion

DTV has several advantages over analog TV, the most significant being that digital channels take up less bandwidth (and the bandwidth needs are continuously variable, at a corresponding cost in image quality depending on the level of compression). This means that digital broadcasters can provide more digital channels in the same space, provide high-definition television service, or provide other non-television services such as multimedia or interactivity. DTV also permits special services such as multiplexing (more than one program on the same channel), electronic program guides and additional languages, spoken or subtitled. The sale of non-television services may provide an additional revenue source. In many cases, viewers perceive DTV to have superior picture quality, improved audio quality, and easier reception than analog.

Disadvantages to conversion

Impact on existing analog technology

The analog switch-off ruling, which so far has met with little opposition from consumers or manufacturers, would render all non-digital televisions obsolete on the switch-off date (February 17, 2009 in the U.S.) unless connected to an external off-the-air tuner, analog or digital cable, or a satellite system. An external converter box (an ATC tuner) can be added to non-digital televisions to lengthen their useful lifespan. Several of these devices have already been shown and, while few were initially available, they are becoming more available by the day. Once connected to the converter unit, operation of non-digital units is seamless and, in most cases, rich in new features (in comparison to previous analog reception operation). In the US, the federal government supports the adoption of digital converters through the mailing of coupons, which cover around 80% of the cost of each unit.

Some existing analog equipment will be less functional with the use of a converter box. For example, television remote controls will no longer be effective at changing channels, because that function will instead be handled by the converter box. Similarly, video recorders for analog signals (including both tape-based VCRs and hard-drive-based DVRs) will not be able to select channels, limiting their ability to automatically record programs via a timer or based on downloaded program information. Also, older, handheld televisions, which rely primarily on over-the-air signals, and battery operation, will be rendered impractical, since the proposed converter boxes are not portable, nor powered with batteries Portable radios which feature the ability to listen to television audio on VHF channels 2-13 would also lose their ability to function, while television stations which formerly broadcast on Channel 6 and were able to have their analog audio heard on common radios using a quirk in the system where their audio could be heard on the far end of the FM band at 87.7, would lose the ability for commuters to listen to their broadcasts.

Any new TVs that contain only an ATSC tuner prevent older devices, such as VCRs and video game consoles with only an analog RF output, from connecting to the TV. Connection would require an analog to digital converter box, which is the opposite as what is currently being sold. Such a box would also likely introduce additional delay into the video signal.

Compression artifacts and allocated bandwidth

DTV images have some picture defects that are not present on analog television or motion picture cinema, because of present-day limitations of bandwidth and compression algorithms such as MPEG-2.

When a compressed digital image is compared with the original program source, some hard-to-compress image sequences may have digital distortion or degradation. For example:

• quantization noise,
• incorrect color,
• blockiness,
• a blurred, shimmering haze.

Broadcasters attempt to balance their needs to show high quality pictures and to generate revenue by using a fixed bandwidth allocation for more services.

Buffering and preload delay

Unlike analog televisions, digital televisions have a significant delay when changing channels, making “channel surfing” more difficult.

Different devices need different amounts of preload time to begin showing the broadcast stream, resulting in an undesirable and annoying audio echo effect when two televisions in adjacent rooms of a house are tuned to the same channel.

Effects of poor reception

Changes in signal reception from factors such as degrading antenna connections or worsening weather conditions may gradually reduce the quality of analog TV. However, the nature of digital TV results in a perfect picture, until the receiving equipment is completely unable to generate a picture at all. This is known as the digital cliff or cliff effect.

For remote locations, distant analog channels that were previously acceptable in a snowy and degraded state may either display perfectly, or be completely unavailable.