HDTV SYSTEM
High-Definition Television (or HDTV) is a digital television broadcasting system with higher resolution than traditional television systems (standard-definition TV, or SDTV).HDTV is digitally broadcast; the earliest implemen tations used analog broadcasting, but today digital television (DTV) signals are used, requiring less bandwidth due to digital video compression.
In 1969, the Japanese state broadcaster NHK first developed consumer high-definition television with a 5:3 aspect ratio, a slightly wider screen format than the usual 4:3 standard. The system, known as Hi-Vision or MUSE after its Multiple sub-Nyquist sampling encoding for encoding the signal, required about twice the bandwidth of the existing NTSC system but provided about four times the resolution. Satellite test broadcasts started in 1989, with regular testing starting in 1991 and regular broadcasting of BS-9ch commenced on 25 November 1994, which featured commercial and NHK programming.
In 1981, the MUSE system was demonstrated for the first time in the United States. It had the same 5:3 aspect ratio as the Japanese system. Upon visiting a demonstration of MUSE in Washington, US President Ronald Reagan was most impressed and officially declared it "a matter of national interest" to introduce HDTV to the USA.
Several systems were proposed as the new standard for the USA, including the Japanese MUSE system, but all were rejected by the FCC because of their higher bandwidth requirements. At the same time that the high definition systems were being studied, the number of television channels was growing rapidly and bandwidth was already fit.A new standard had to be radically efficient, needing less bandwidth for HDTV than the existing NTSC standard for SDTV.
Contemporary systems
Components of a typical satellite HDTV system:1. HDTV Monitor2. HD satellite receiver3. Standard satellite dish4. HDMI cable, DVI-D and audio cables, or audio and component video cables
Besides an HD-ready television set, other equipment is needed to view HD television. Cable-ready TV sets can display HD content without using an external box. They have a QAM tuner built-in and/or a card slot for inserting a CableCARD.[28]
High-definition image sources include terrestrial broadcast, direct broadcast satellite, digital cable, the high definition disc BD, Internet downloads, the PlayStation 3, and the Xbox 360.
High-definition display resolutions
High Definition usually refers to 720 or more lines of video format resolution displayed in a horizontal fashion from top to bottom.
A common native resolution used in HD Ready LCD TV panels is 1366 x 768 pixels instead of the ATSC Standard 1280 x 720 pixels. This is due to maximization of manufacturing yield and resolution of VGA, VRAM that comes with a 768 pixel format. Hence, LCD manufacturers adopt the 16:9 ratio compatible for the HD Ready 1080p video standard. Nevertheless, every HDTV has an overscan processing chipset to fix resolution scaling and color rendering, eg LG XD Engine, SONY BRAVIA Engine. Only when viewing 1080i/1080p HD contents under HD Ready 1080p where there is true pixel-for-pixel reproduction, and for HD ready LCD TV, do some signals undergo a scaling process which results in a 3-5% loss of picture.
It should be noted that the numbers used for "HD-Ready" image resolutions do not constitute acceptable 750- or 1125-line video signals in most standards-compliant hardware; in this respect terms such as "720p" and "1080p" are mostly used for advertising, though that does not necessarily mean that HD-Ready TVs labeled in this manner are incapable of accepting those formats as input.
Additionally, the "Clean Aperture" numbers are almost always contained within the frames of their respective "Production Aperture" numbers (e.g., a 1888×1062 rectangle would be contained within a 1920×1080 frame). This is to maintain compatibility with analog signals, which can often become distorted close to the edge of the frame. It also increases the chance that a digital signal being played on overscan-enabled equipment will display the entire picture visibly.
Recording and compression
HDTV can be recorded to D-VHS (Digital-VHS or Data-VHS), W-VHS (analog only), to an HDTV-capable digital video recorder (for example DirecTV's high-definition Digital video recorder, Sky HD's set-top box, Dish Network's VIP 622 or VIP 722 high-definition Digital video recorder receivers, or TiVo's Series 3 or HD recorders), or an HDTV-ready HTPC. Some cable boxes are capable of receiving or recording two or more broadcasts at a time in HDTV format, and HDTV programming, some free, some for a fee, can be played back with the cable company's on-demand feature.
The massive amount of data storage required to archive uncompressed streams meant that inexpensive uncompres sed storage options were not available in the consumer market until recently. In 2008 the Hauppage 1212 Personal Video Recorder was introduced. This device accepts HD content through component video inputs and stores the content in an uncompressed MPEG transport stream (.ts) file or Blu-ray format .m2ts file on the hard drive or DVD burner of a computer connected to the PVR through a USB 2.0 interface.
Realtime MPEG-2 compression of an uncompressed digital HDTV signal is prohibitively expensive for the consumer market at this time, but should become inexpensive within several years (although this is more relevant for consumer HD camcorders than recording HDTV). Analog tape recorders with bandwidth capable of recording analog HD signals such as W-VHS recorders are no longer produced for the consumer market and are both expensive and scarce in the secondary market.
In the United States, as part of the FCC's "plug and play" agreement, cable companies are required to provide customers who rent HD set-top boxes with a set-top box with "functional" Firewire (IEEE 1394) upon request. None of the direct broadcast satellite providers have offered this feature on any of their supported boxes, but some cable TV companies have. As of July 2004[update], boxes are not included in the FCC mandate. This content is protected by encryption known as 5C.This encryption can prevent duplication of content or simply limit the number of copies permitted, thus effectively denying most if not all fair use of the content.
Broadcast station format considerations
At a minimum, HDTV has twice the linear resolution of standard-definition television (SDTV), thus showing greater detail than either analog television or regular DVD. The technical standards for broadcasting HDTV also handle the 16:9 aspect ratio images without using letterboxing or anamorphic stretching, thus increasing the effective image resolution.
The optimum format for a broadcast depends upon the type of videographic recording medium used and the image's characteristics. The field and frame rate should match the source and the resolution. A very high resolution source may require more bandwidth than available in order to be transmitted without loss of fidelity. The lossy compression that is used in all digital HDTV storage and transmission systems will distort the received picture, when compared to the uncompressed source.
Notation
HDTV broadcast systems are identified with three major parameters:
Frame size in pixels is defined as number of horizontal pixels x number of vertical pixels, for example 1280 x 720 or 1920 x 1080. Often the number of horizontal pixels is implied from context and is omitted.
Scanning system is identified with the letter p for progressive scanning or i for interlaced scanning.
Frame rate is identified as number of video frames per second. For interlaced systems an alternative form of specifying number of fields per second is often used. Recently the uniform notation of specifying number of frames per second both for progressive and interlaced video has become increasingly popular.
High-Definition Television (or HDTV) is a digital television broadcasting system with higher resolution than traditional television systems (standard-definition TV, or SDTV).HDTV is digitally broadcast; the earliest implemen tations used analog broadcasting, but today digital television (DTV) signals are used, requiring less bandwidth due to digital video compression.
In 1969, the Japanese state broadcaster NHK first developed consumer high-definition television with a 5:3 aspect ratio, a slightly wider screen format than the usual 4:3 standard. The system, known as Hi-Vision or MUSE after its Multiple sub-Nyquist sampling encoding for encoding the signal, required about twice the bandwidth of the existing NTSC system but provided about four times the resolution. Satellite test broadcasts started in 1989, with regular testing starting in 1991 and regular broadcasting of BS-9ch commenced on 25 November 1994, which featured commercial and NHK programming.
In 1981, the MUSE system was demonstrated for the first time in the United States. It had the same 5:3 aspect ratio as the Japanese system. Upon visiting a demonstration of MUSE in Washington, US President Ronald Reagan was most impressed and officially declared it "a matter of national interest" to introduce HDTV to the USA.
Several systems were proposed as the new standard for the USA, including the Japanese MUSE system, but all were rejected by the FCC because of their higher bandwidth requirements. At the same time that the high definition systems were being studied, the number of television channels was growing rapidly and bandwidth was already fit.A new standard had to be radically efficient, needing less bandwidth for HDTV than the existing NTSC standard for SDTV.
Contemporary systems
Components of a typical satellite HDTV system:1. HDTV Monitor2. HD satellite receiver3. Standard satellite dish4. HDMI cable, DVI-D and audio cables, or audio and component video cables
Besides an HD-ready television set, other equipment is needed to view HD television. Cable-ready TV sets can display HD content without using an external box. They have a QAM tuner built-in and/or a card slot for inserting a CableCARD.[28]
High-definition image sources include terrestrial broadcast, direct broadcast satellite, digital cable, the high definition disc BD, Internet downloads, the PlayStation 3, and the Xbox 360.
High-definition display resolutions
High Definition usually refers to 720 or more lines of video format resolution displayed in a horizontal fashion from top to bottom.
A common native resolution used in HD Ready LCD TV panels is 1366 x 768 pixels instead of the ATSC Standard 1280 x 720 pixels. This is due to maximization of manufacturing yield and resolution of VGA, VRAM that comes with a 768 pixel format. Hence, LCD manufacturers adopt the 16:9 ratio compatible for the HD Ready 1080p video standard. Nevertheless, every HDTV has an overscan processing chipset to fix resolution scaling and color rendering, eg LG XD Engine, SONY BRAVIA Engine. Only when viewing 1080i/1080p HD contents under HD Ready 1080p where there is true pixel-for-pixel reproduction, and for HD ready LCD TV, do some signals undergo a scaling process which results in a 3-5% loss of picture.
It should be noted that the numbers used for "HD-Ready" image resolutions do not constitute acceptable 750- or 1125-line video signals in most standards-compliant hardware; in this respect terms such as "720p" and "1080p" are mostly used for advertising, though that does not necessarily mean that HD-Ready TVs labeled in this manner are incapable of accepting those formats as input.
Additionally, the "Clean Aperture" numbers are almost always contained within the frames of their respective "Production Aperture" numbers (e.g., a 1888×1062 rectangle would be contained within a 1920×1080 frame). This is to maintain compatibility with analog signals, which can often become distorted close to the edge of the frame. It also increases the chance that a digital signal being played on overscan-enabled equipment will display the entire picture visibly.
Recording and compression
HDTV can be recorded to D-VHS (Digital-VHS or Data-VHS), W-VHS (analog only), to an HDTV-capable digital video recorder (for example DirecTV's high-definition Digital video recorder, Sky HD's set-top box, Dish Network's VIP 622 or VIP 722 high-definition Digital video recorder receivers, or TiVo's Series 3 or HD recorders), or an HDTV-ready HTPC. Some cable boxes are capable of receiving or recording two or more broadcasts at a time in HDTV format, and HDTV programming, some free, some for a fee, can be played back with the cable company's on-demand feature.
The massive amount of data storage required to archive uncompressed streams meant that inexpensive uncompres sed storage options were not available in the consumer market until recently. In 2008 the Hauppage 1212 Personal Video Recorder was introduced. This device accepts HD content through component video inputs and stores the content in an uncompressed MPEG transport stream (.ts) file or Blu-ray format .m2ts file on the hard drive or DVD burner of a computer connected to the PVR through a USB 2.0 interface.
Realtime MPEG-2 compression of an uncompressed digital HDTV signal is prohibitively expensive for the consumer market at this time, but should become inexpensive within several years (although this is more relevant for consumer HD camcorders than recording HDTV). Analog tape recorders with bandwidth capable of recording analog HD signals such as W-VHS recorders are no longer produced for the consumer market and are both expensive and scarce in the secondary market.
In the United States, as part of the FCC's "plug and play" agreement, cable companies are required to provide customers who rent HD set-top boxes with a set-top box with "functional" Firewire (IEEE 1394) upon request. None of the direct broadcast satellite providers have offered this feature on any of their supported boxes, but some cable TV companies have. As of July 2004[update], boxes are not included in the FCC mandate. This content is protected by encryption known as 5C.This encryption can prevent duplication of content or simply limit the number of copies permitted, thus effectively denying most if not all fair use of the content.
Broadcast station format considerations
At a minimum, HDTV has twice the linear resolution of standard-definition television (SDTV), thus showing greater detail than either analog television or regular DVD. The technical standards for broadcasting HDTV also handle the 16:9 aspect ratio images without using letterboxing or anamorphic stretching, thus increasing the effective image resolution.
The optimum format for a broadcast depends upon the type of videographic recording medium used and the image's characteristics. The field and frame rate should match the source and the resolution. A very high resolution source may require more bandwidth than available in order to be transmitted without loss of fidelity. The lossy compression that is used in all digital HDTV storage and transmission systems will distort the received picture, when compared to the uncompressed source.
Notation
HDTV broadcast systems are identified with three major parameters:
Frame size in pixels is defined as number of horizontal pixels x number of vertical pixels, for example 1280 x 720 or 1920 x 1080. Often the number of horizontal pixels is implied from context and is omitted.
Scanning system is identified with the letter p for progressive scanning or i for interlaced scanning.
Frame rate is identified as number of video frames per second. For interlaced systems an alternative form of specifying number of fields per second is often used. Recently the uniform notation of specifying number of frames per second both for progressive and interlaced video has become increasingly popular.
