Analog high-definition television has referred to a variety of analog video broadcast television systems with various display resolutions throughout history.
On 2 November 1936 the BBC began transmitting the world's first public regular analog "high definition" television service from the Victorian Alexandra Palace in north London.It therefore claims to be the birthplace of television broadcasting as we know it today. The UK's 405-line system introduced in 1936 was described as "high definition"; however, this was in comparison with the early 30-line (largely) experimental system from the 1920s, and would not be considered high definition by modern standards.
John Logie Baird, Philo T. Farnsworth, and Vladimir Zworykin had each developed competing TV systems, but resolution was not the issue that separated their substantially different technologies, it was patent interference lawsuits and deployment issues given the tumultuous financial climate of the late 1920s and 1930s. Most patents were expiring by the end of World War II leaving no worldwide standard for television. The standards introduced in the early 1950s stayed for over half a century.
When Europe resumed TV transmissions after WWII (i.e. in the late 1940s and early 1950s) most countries standardized on a 576i (625-line) television system. The two exceptions were the British 405-line system, which had already been introduced in 1936, and the French 819-line system. During the 1940s René Barthélemy already reached 1,015 lines and even 1,042 lines. On November 20, 1948, François Mitterrand, the then Secretary of State for Information, decreed a broadcast standard of 819 lines developed by Henri de France; broadcasting began at the end of 1949 in this definition.
This was arguably the world's first high-definition television system, and, by today's standards, it could be called 736i (as it had 737 lines active, but one of the lines was composed of 2 halves) MHz of VHF bandwidth.with a maximum theoretical resolution of 408×368 line pairs (which in digital terms can be expressed as broadly equivalent to 816×736 pixels) with a 4:3 aspect ratio. It was used only in France by TF1, and in Monaco by Tele Monte Carlo. However, the theoretical picture quality far exceeded the capabilities of the equipment of its time, and each 819-line channel occupied a wide 14
By comparison, the modern 720p standard is 1,280×720 pixels, of which the 4:3 portion would be 960×720 pixels, while PAL DVDs have a resolution of 720×576 pixels.
Television channels were arranged as follows:
|Ch||picture (MHz)||sound (MHz)|
Technical specifications of the broadcast television systems used with 819-lines.
|Field frequency||Active picture||Field blanking||No. of broad pulses||Broad pulse width||Line frequency||Front porch||Line sync||Back porch||Active line time||Video/syncs ratio|
|50 Hz||737-lines||41-lines||1 per field||20.0 μs||20475 Hz||0.5 μs||2.5 μs||5.0 μs||40.8 μs||70/30|
|System||Lines||Frame rate||Channel bandwidth (in MHz)||Visual bandwidth (in MHz)||Sound offset||Vestigial sideband||Vision mod.||Sound mod.|
|System E||819||25||14||10||±11.15 (Sound carrier separation +11.15 MHz on odd numbered channels, -11.15 MHz on even numbered channels.)||2.00||Pos.||AM|
System E implementation provided very good (near HDTV) picture quality but with an uneconomical use of bandwidth; a 625/50 signal providing the same clarity as an 819-line image, but matted down 4:3 with the same number of lines, would still need nearly 6 MHz for the vision carrier alone (vs typical 5 to 6 MHz in actual use), and 5 MHz for 525/60 (vs typical 4.2 MHz), although a 405/50 transmission could get away with only 2.5 MHz (typical 3 MHz, as System A made no allowance for the Kell factor and thus had a "narrow pixel"/"tall line" appearance). Thus even an unusually crisp "standard" definition (or slightly soft 405-line) image only needed half, or even one-quarter the vision bandwidth of the 819-line system to give a "balanced" appearance, despite their lower overall resolution still seeming perfectly clear on the more affordable small-screen receivers often used in the pre-color era. With the usual additions of sound carrier and vestigial sideband the result was a combined signal that demanded approximately two to three times the bandwidth of more moderately specified standards, even when colour was added to them (as the color subcarrier resides within the luma signal space).
System F was an adapted 819-line system used in Belgium and Luxembourg as an answer to this problem, with only half the vision bandwidth and approximately half the sound carrier offset. It allowed French 819-line programming to squeeze into the 7 MHz VHF broadcast channels used in those neighbouring countries, albeit with a substantial loss of horizontal resolution (408×737 effective); although this still offered approximately twice the actual clarity of 405-line System A (twice the lines, roughly the same horizontal definition), the contrast between vertical and horizontal resolution would have made it seem perceptually worse. Use of System F was discontinued in Belgium in February 1968, and in Luxembourg in September 1971.
Despite some attempts to create a color SECAM version of the 819-line system (which would have then also had the highest pre-HDTV colour signal resolution, with lines of FM encoding alternately centred on 8.82 and 8.5 MHz, if arranged similarly to 625-line SECAM), France gradually abandoned it in favor of the Europe-wide standard of 625-lines (576i50), with the final 819-line transmissions in Metropolitan France taking place in Paris from the Eiffel Tower on 19 July 1983. TMC in Monaco were the last broadcasters to transmit 819-line television, closing down their System E transmitter in 1985.
However, between 1976 and 1981 when French channel TF1 was switching area by area to the new analog 625-lines UHF network with SECAM color, some transmitters and gapfillers broadcast the 819-line signal in UHF.When switching to 625-lines, most gapfillers did not change UHF channel (e.g. many gapfillers using this transmission located in French Alps near Grenoble, Mont Salève and Geneva began broadcasting on UHF channel 42, and continue to use this frequency to this day). They were switched to 625-lines in June 1981.
Japan had the earliest working HDTV system, with design efforts going back to 1979. The country began broadcasting wideband analog high-definition video signals in the late 1980s using an interlaced resolution of 1035 or 1080-lines active (1035i) and 1125-lines total (up to 1875x1125 in digital terms) total supported by the Sony HDVS line of equipment.
The Japanese system, developed by NHK Science & Technology Research Laboratories in the 1980s, employed filtering tricks to reduce the original source signal to decrease bandwidth utilization. MUSE was marketed as "Hi-Vision" by NHK. Japanese broadcast engineers rejected conventional vestigial sideband broadcasting to allow transmitting a HD signal on a tighter bandwidth. It was decided early on that MUSE would be a satellite broadcast format as Japan economically supports satellite broadcasting.
In the typical setup, three picture elements on a line were actually derived from three separate scans. Stationary images were transmitted at full resolution. However, as MUSE lowers the horizontal and vertical resolution of material that varies greatly from frame to frame, moving images were blurred in a manner similar to using 16 mm movie film for HDTV projection. In fact, whole-camera pans would result in a loss of 50% of horizontal resolution. Shadows and multipath still plague this analog frequency modulated transmission mode.
MUSE's "1125-lines" are an analog measurement, which includes non-video "scan lines" during which a CRT's electron beam returns to the top of the screen to begin scanning the next field. Only 1035-lines have picture information.Digital signals count only the lines (rows of pixels) of the picture makeup as there are no other scanning lines (though conversion to an analogue format will introduce them), so NTSC's 525-lines become 480i, and MUSE would be 1035i.
Japan has since switched to a digital HDTV system based on ISDB; The original MUSE-based BS Satellite channel 9 (NHK BS Hi-vision) ended transmitting on November 30, 2007,moving to BS-digital channel 103.
Subsampling lives on in modern MPEG systems based on JPEG coding, as JPEG offers Chroma sub-sampling. High quality HD television has a sampling structure approximating 4:2:1 (Luma : Chroma : Saturation) for reference images (I-Frames), though 4:0.75:0.65 is probably typical for multi-channel delivery.
HD-MAC was a proposed television standard by the European Commission in 1986 (MAC standard) . It was an early attempt by the EEC to provide HDTV in Europe. It was a complex mix of analog signal (Multiplexed Analog Components) multiplexed with digital sound. The video signal (1,250 (1,152 visible) lines/50 frames in 16:9 aspect ratio) was encoded with a modified D2-MAC encoder.
For the 1992 Summer Olympics experimental HD-MAC broadcasting took place. 100 HD-MAC receivers (in that time, retroprojectors) in Europe were used to test the capabilities of the standard. This project was financed by the European Union (EU). The PAL-converted signal was used by mainstream broadcasters such as SWR, BR and 3Sat.
The HD-MAC standard was abandoned in 1993, and since then all EU and EBU efforts have focused on the DVB system (Digital Video Broadcasting), which allows both SDTV and HDTV.
The analog TV systems these systems were meant to replace
Digital television (DTV) is the transmission of television audiovisual signals using digital encoding, in contrast to the earlier analog television technology which used analog signals. At the time of its development it was considered an innovative advancement and represented the first significant evolution in television technology since color television in the 1950s. Modern digital television is transmitted in high definition (HDTV) with greater resolution than analog TV. It typically uses a widescreen aspect ratio in contrast to the narrower format of analog TV. It makes more economical use of scarce radio spectrum space; it can transmit up to seven channels in the same bandwidth as a single analog channel, and provides many new features that analog television cannot. A transition from analog to digital broadcasting began around 2000. Different digital television broadcasting standards have been adopted in different parts of the world; below are the more widely used standards:
The abbreviation NTSC can refer to the National Television System Committee, which developed the analog television color system that was introduced in North America in 1954 and stayed in use until digital conversion. NTSC is also an abbreviation for the National Television Standards Committee, a subset of the National Television System Committee that was responsible for producing the detailed technical specifications for the transmission standard. It is one of three major analog color television standards, the others being PAL and SECAM.
Phase Alternating Line (PAL) is a colour encoding system for analogue television used in broadcast television systems in most countries broadcasting at 625-line / 50 field per second (576i). It was one of three major analogue colour television standards, the others being NTSC and SECAM.
Standard-definition television is a television system which uses a resolution that is not considered to be either high or enhanced definition. SDTV and high-definition television (HDTV) are the two categories of display formats for digital television (DTV) transmissions. "Standard" refers to the fact that it was the prevailing specification for broadcast television in the mid- to late-20th century.
SECAM, also written SÉCAM, is an analog color television system first used in France. It was one of three major color television standards, the others being PAL and NTSC.
Interlaced video is a technique for doubling the perceived frame rate of a video display without consuming extra bandwidth. The interlaced signal contains two fields of a video frame captured consecutively. This enhances motion perception to the viewer, and reduces flicker by taking advantage of the phi phenomenon.
Advanced Television Systems Committee (ATSC) standards are an American set of standards for digital television transmission over terrestrial, cable and satellite networks. It is largely a replacement for the analog NTSC standard and, like that standard, is used mostly in the United States, Mexico, Canada, and South Korea. Several former NTSC users, in particular Japan, have not used ATSC during their digital television transition, because they adopted their own system called ISDB.
Broadcast television systems are the encoding or formatting standards for the transmission and reception of terrestrial television signals. There were three main analog television systems in use around the world until the late 2010s: NTSC, PAL, and SECAM. Now in digital terrestrial television (DTT), there are four main systems in use around the world: ATSC, DVB, ISDB and DTMB.
PALplus is an analogue television broadcasting system aimed to improve and enhance the PAL format while remaining compatible with existing television receivers. It followed experiences with the HD-MAC and D2-MAC, hybrid analogue-digital formats that were incompatible with PAL receivers. It was developed at the University of Dortmund in Germany, in cooperation with German terrestrial broadcasters and European and Japanese manufacturers.
HD-MAC was a proposed broadcast television systems standard by the European Commission in 1986, a part of Eureka 95 project. It is an early attempt by the EEC to provide High-definition television (HDTV) in Europe. It is a complex mix of analogue signal, multiplexed with digital sound, and assistance data for decoding (DATV). The video signal was encoded with a modified D2-MAC encoder.
720p is a progressive HDTV signal format with 720 horizontal lines and an aspect ratio (AR) of 16:9, normally known as widescreen HDTV (1.78:1). All major HDTV broadcasting standards include a 720p format, which has a resolution of 1280×720; however, there are other formats, including HDV Playback and AVCHD for camcorders, that use 720p images with the standard HDTV resolution. The frame rate is standards-dependent, and for conventional broadcasting appears in 50 progressive frames per second in former PAL/SECAM countries, and 59.94 frames per second in former NTSC countries.
1080i is a combination of frame resolution and scan type. 1080i is used in high-definition television (HDTV) and high-definition video. The number "1080" refers to the number of horizontal lines on the screen. The "i" is an abbreviation for "interlaced"; this indicates that only the odd lines, then the even lines of each frame are drawn alternately, so that only half the number of actual image frames are used to produce video. A related display resolution is 1080p, which also has 1080 lines of resolution; the "p" refers to progressive scan, which indicates that the lines of resolution for each frame are "drawn" on the screen in sequence.
576i is a standard-definition video mode originally used for terrestrial television in most countries of the world where the utility frequency for electric power distribution is 50 Hz. Because of its close association with the colour encoding system, it is often referred to as simply PAL, PAL/SECAM or SECAM when compared to its 60 Hz NTSC-colour-encoded counterpart, 480i. In digital applications it is usually referred to as "576i"; in analogue contexts it is often called "625 lines", and the aspect ratio is usually 4:3 in analogue transmission and 16:9 in digital transmission.
576p is the shorthand name for a video display resolution. The p stands for progressive scan, i.e. non-interlaced, the 576 for a vertical resolution of 576 pixels, usually with a horizontal resolution of 768 or 1024, depending of the relationship aspect. The 576p quality was decided as the default quality when converting from VHS to digital. 576p is considered standard definition for PAL video. The frame rate can be given explicitly after the letter.
High-definition video is video of higher resolution and quality than standard-definition. While there is no standardized meaning for high-definition, generally any video image with considerably more than 480 vertical scan lines or 576 vertical lines (Europe) is considered high-definition. 480 scan lines is generally the minimum even though the majority of systems greatly exceed that. Images of standard resolution captured at rates faster than normal, by a high-speed camera may be considered high-definition in some contexts. Some television series shot on high-definition video are made to look as if they have been shot on film, a technique which is often known as filmizing.
Multiplexed analogue components (MAC) was a satellite television transmission standard, originally proposed for use on a Europe-wide terrestrial HDTV system, although it was never used terrestrially.
MUSE, was an analog high-definition television system, using dot-interlacing and digital video compression to deliver 1125-line high definition video signals to the home. Japan had the earliest working HDTV system, MUSE, which was named Hi-Vision with design efforts going back to 1979. The country began broadcasting wideband analog HDTV signals in 1989 using 1035 active lines interlaced in the standard 2:1 ratio (1035i) with 1125 lines total. By the time of its commercial launch in 1991, digital HDTV was already under development in the United States. Hi-Vision continued broadcasting in analog until 2007.
Television standards conversion is the process of changing a television transmission or recording from one television system to another. The most common is from NTSC to PAL or the other way around. This is done so television programs in one nation may be viewed in a nation with a different standard. The video is fed through a video standards converter, which makes a copy in a different video system.
High-definition television (HD) describes a television system providing an image resolution of substantially higher resolution than the previous generation of technologies. The term has been used since 1936, but in modern times refers to the generation following standard-definition television (SDTV), often abbreviated to HDTV or HD-TV. It is the current de facto standard video format used in most broadcasts: terrestrial broadcast television, cable television, satellite television, and Blu-ray Discs.
CCIR System I is an analog broadcast television system. It was first used in the Republic of Ireland starting in 1962 as the 625-line broadcasting standard to be used on VHF Band I and Band III, sharing Band III with 405-line System A signals radiated in the north and east of the country. The UK started its own 625-line television service in 1964 also using System I, but on UHF only – the UK has never used VHF for 625-line television except for some cable relay distribution systems.