Table 1: Formats for SD/HDTV, non integer figures are omitted for clarity
Figure 1: SD and HDTV, a comparison with diff aspect ratios and resolutions.
HDTV is offering the highest quality pictures available in today’s entertainment world. It uses 720 or 1080 lines to plot a picture rather than a conventional 576 lines. The pixels in the lines are too close and results in very improved picture quality, colour definition and clarity factors [4].
Audio is also improved. The ATSC standards call for AC3 or Dolby Digital sound, which can provide 24-bit 5.1 surround sound.
Technical Aspects of HDTV:
The technical aspects of HDTV discussed in this paper will cover following main points.
- Delivery of The Service
- Technical Specifications in HDTV Transmission
- Need of Standards for HDTV
- International Roll out of HDTV
- Market development for HD-ready receivers, recording/playback equipment and Set-top boxes
Delivery of the Service:
In HDTV transmission, the television screen displays the picture as an HDTV camera(s) captures the signal (or may be converted from any other format with HDTV Equipment). There is a HDTV transmitter that transmits the signal to the receiver and then it is displayed on HDTV compatible TV set. There are 18 DTV formats and among them six are HDTV formats, as prescribed by the Advanced Televisions Systems Committee. HDTV can receive entire 18 digital television formats.
Delivery of service includes the bandwidth, video compression and audio techniques, broadcasting standards used and the type of scanning to retrieve the HDTV transmission at receiver end.
Video Compression, in HDTV is initially done the MPEG-2. Initially MPEG-2 and H.264/MPEG-4 AVC are used. These allows the bandwidth of a single STV 96MHz to carry up to 5 standard or 2 high definition DTV channels instead. Conventionally MPEG-2 supports 10-bit quantization, but in HDTV the broadcasters uses 8-bit quantization to save the bandwidth. But the introduction of DVB-S2 has aided to save the bandwidth more than the prior techniques by the use of MPEG-4. The majority of HDTV services in Europe are now using MPEG-4 compression technique which includes Germany (Premiere), Spain (Canal+), France (CanalSat) etc [5].
The MPEG-4 AVC standard has also been selected for the roll-out of HD services on other television platforms such as satellite and IPTV, as well as in associated consumer audiovisual equipment such as game consoles, camcorders and portable video handsets. Such widespread use of the standard should spur further compression improvements and also help reduce the unit cost of MPEG-4 AVC coding equipment. The signs are also positive that MPEG-4 AVC decoding products are beginning to reach the mass market at acceptable prices [6].
Audio in HDTV is of very good quality. Because it uses the Dolby Digital (AC-3) format to support “5.1” enabling full surround sound capability.
Technical Specifications in HDTV Transmission:
∙ HDTV Resolution:
Following are some technical definitions for the resolution used in HDTV.
Scanning HDTV enabled sets support both interlaced and progressive scan
Technologies, further explained in the following section.
Aspect Ratio ATSC has adopted the 16:9 "Wide-Screen" aspect ratio for HDTV
because significantly more information can be displayed on the screen
by using this aspect ratio.
Frame Rate Interlaced scan contents draw pictures in 2 phases even numbered
lines and odd numbered lines) and the pictures refreshes half often as
a progressive scan image with the same frame rate. 1080p, 720p uses
24 frames per second (fps), 720p uses 60 fps and 1080i uses 30 fps.
Sound In addition to the sharper picture, HDTV broadcasts incorporate a
Dolby® Digital 5.1 sound system.
Compression HDTV uses MPEG-2 compression scheme to fit in the high quality of
image and sound in the broadcast stream.
The HDTV screen format prescribes the scanning mode, image resolution, and frame rate. The scanning mode remained the most controversial aspect of the HDTV technology. Two scanning modes are available for display:
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Interlaced Scan is a scanning mode; the odd numbers of horizontal lines are first scanned from top to bottom. The even numbers of horizontal lines are subsequently scanned from top to bottom. The NTSC standard (as well as other TV standards in Europe) prescribes the interlaced scanning mode.
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Progressive Scan is a scanning mode; the whole set of the horizontal lines are scanned altogether from top to bottom. The scanning format of computer monitor screens is progressive.
Figure 2: Showing the two techniques of scanning used by HDTV.
Standards of HDTV:
There are different HDTV standards adopted by different countries. HDTV broadcast standards are include ATSC’s (North America, parts of Central America and South Korea), DVB (Europe, Australia, parts of Asia, South America and Africa) and ISDB-T (Japan, Brazil).
HDTV video recordings are recorded in 720p, 1080i or 1080p format. ‘p’ stands for ‘progressive’ and ‘i’ stands for ’interlaced’, these are two modes of scanning done in HDTV (discussed in the previous section). The format depends on the broadcast company if destined for television broadcast, however in other scenarios the format choice will vary depending on a variety of factors. In general, 720p is more appropriate for fast action as it uses progressive fields, as opposed to 1080i which uses interlaced fields and thus can have a degradation of image quality with fast motion.
In addition, 720p is used more often with internet distribution of HD video, as all computer monitors are progressive, and most graphics cards do a sub-optimal job of de-interlacing video in real time. 720p Video also has lower storage and recoding requirements than 1080i or 1080p.
Following table gives brief but comprehensive information about the two formats.
Table 2: Difference b/w HDTV 720p and 1080i
Need of Standards:
There are two scanning formats progressive and interlaced. The scanning format of computer monitor screens is progressive and for the conventional television is interlaced scan. It is henceforth conceivable that the dispute over scanning mode would inevitably lead to a battle between the TV broadcasters and the computer industry.
The controversy over scanning mode was present at the beginning of the Grand Alliance. Among the four HDTV proponents, the AT&T/Zenith system and the MIT/GI system adopted the progressive scanning mode, while the Philips/Sarnoff/ Thomson/ NBC system and the GI system used the interlaced scanning mode. The debate was twofold. First, this issue was associated with priority over TV broadcasting enterprises or computer industry as for the broadcasters, an interlaced scanned HDTV as a continuation from the conventional NTSC TV remained the better choice since the current video broadcasting format did not have to alter drastically. For the proponents more closely connected with computer industry or ``envisioned'' the future of HDTV to be a part of the integrated digital infrastructure, the progressive scanning mode could render a TV set a terminal station of the computer network without essential difficulty [7].
Now there is a real need to adopt a standard for HDTV because the vendors who are making the HDTV compatible equipment to different standards. Because the technology can take revolutionary spell after the standards are published and adopted. This will also aid the consumers that are not sure for the equipment they should buy, because there is no one standard. So making the standard for HDTV will stop the battle b/w there TV and computer industry, one broadcast standard will be very healthy step for the technology, the vendors of the product (HDTV compatible) and also for the end user (the customers).
International Roll-Out of HDTV:
HDTV services can be delivered to user premises using the existing transmission platforms including terrestrial television channels, cable television system, satellites and broadband telecommunications networks. Some countries, which have an early start in the implementation of digital television broadcasting, like United States, Europe, Japan and Australia have launched HDTV broadcasts.
The US industry had expected that many viewers would choose to watch HDTV programmes using the terrestrially-delivered digital TV services based on the ATSC standard. In spite of this, the majority of HDTV viewers are choosing to take HDTV programmes from their cable or satellite provider. Cable companies in particular have seen great success with HDTV over the past year and both they and satellite providers DirecTV and EchoStar view it as a strategic priority to support customer retention in the future.
Recent Impact of HDTV in UK:
In UK, the first switch off of analogue television happened on 30 March 2005, in the villages of Wales. Major cities in UK are digitized now and are delivering HD service e.g. Sky has offered an exclusive service called Sky HD where consumer will be given a different set-up box to receive HD channels. HOUSEHOLDS in Greater Manchester U.K. have until November next year to ensure they have a TV or set-top box capable of receiving digital signals of HDTV. Digital UK revealed that the switch-off of the analogue signal beamed across the Granada region from Winter Hill in Bolton will begin on November 4, 2009, when BBC2 will be switched off. The remaining channels will be switched off on December 2, 2009. People who have not yet invested in a Free view television or set-top box, or signed up to a cable or satellite service, have just over a year to ensure they can receive digital television signals [8].
Figure 3: Shows the ratio of HDTV sold and, price of HDTV b/w 2002 to 2007.
Market Development of Set-Top boxes, HD Equipment:
In 2008, most countries enhanced their migration process to digital TV before the Olympic Games to ensure more users could watch the Games with digital TV. Sales revenue for the STB market in the first nine months of this year reached CNY 5.87bn (US$ 860mn), up 53.1% from the same period of 2007, and is predicted to reach CNY 7.74bn for 2008 as a whole The increasing sales volume for high-definition, bi-directional and other high-end STB products slowed the downslide trend in price of STB products, which in turn drove up sales revenue, according to the research firm.
Competition within the country's STB market was found to have heated up in 2008, and more firms undertook co-operations with digital TV operators, as STB manufacturers and digital TV operators undertook risk and shared profits together.
In terms of pay-TV platforms, digital terrestrial television (DTT) set-top box manufacturers benefited from the establishment of DTT systems in Beijing, Shanghai, Shenzen, Tianjian and other cities in 2008, with trials undertaken in Qinhuangdo, Qingdao, Shenyang, Guangzhou and other cities. Toshiba and other firms also released television models with integrated DTT tuners, and the emerging production of TVs with integrated DTT tuners is expected to have an increasing impact on STB sales.
China's set-top box market will maintain the steady growth it has enjoyed so far in 2008 to year-end, thanks to the strong performance of the country's digital TV industry, especially cable digital TV, and according to a new report from Chinese research firm CCID Consulting [9].
Conclusion:
However, it is considers that the computer will remain the dominant platform for residential access to interactive services partly due to the higher current installed base of computer/modem households and partly due to the sluggish development and up-take of digital TV offerings in Europe.
Figure 4: Shows the set-top boxes installed in Europe and the US
References:
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DTV Glossary, Retrieved: November 25, 2008, retrieved My ETV South Carolina, from Website: http://www.myetv.org/television/dtv/glossa2ry.cfm
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Systems and Applications. Fifth Annual European Computer Conference. Proceedings, 1991-05-13 Telev, Study Centre of Nat. Res. Council, Torino Italy.
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HDTV Introduction, Retrieved on Nov 29, 2008 from Website: http://www.hdtvorg.co.uk/guide/hdtv/introduction.htm
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Key Issues for the Broadcasters, regulators and Viewers, Retrieved on Dec 02, 2008 From Website: http://www.digitag.org/HDTV_v01.pdf
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Salvador Alvarez, James Chen, David Lecumberri, HDTV: The Engineering History, Retrieved On Dec 03, 2008 from Website: http://web.mit.edu/6.933/www/HDTV.pdf.
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