Analog high-definition television system


Analog high-definition television was an analog video broadcast television system developed in the 1930s to replace early experimental systems with as few as 12-lines. 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. 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.
The UK's 405-line system introduced in 1936 was described as "high definition". However, this was in comparison with the early 30-line experimental system from the 1920s, and would not be considered high definition by modern standards.

French 819-line system

When Europe resumed TV transmissions after WWII most countries standardized on a 576i 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 with a maximum theoretical resolution of 408×368 line pairs 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 MHz of VHF bandwidth.
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:
Chpicture sound
F252.4041.25
F465.5554.40
F5164.00175.15
F6173.40162.25
F7177.15188.30
F8186.55175.40
F8a185.25174.10
F9190.30201.45
F10199.70188.55
F11203.45214.60
F12212.85201.70

Technical specifications of the broadcast television systems used with 819-lines.
Field frequencyActive pictureField blankingNo. of broad pulsesBroad pulse widthLine frequencyFront porchLine syncBack porchActive line timeVideo/syncs ratio
50 Hz737-lines41-lines1 per field20.0 μs20475 Hz0.5 μs2.5 μs5.0 μs40.8 μs70/30

SystemLinesFrame rateChannel bandwidth Visual bandwidth Sound offsetVestigial sidebandVision mod.Sound mod.
System E819251410±11.15 2.00Pos.AM
System F8192575+5.50.75Pos.AM

System E implementation provided very good 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, and 5 MHz for 525/60, although a 405/50 transmission could get away with only 2.5 MHz. Thus even an unusually crisp "standard" definition 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.
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 ; although this still offered approximately twice the actual clarity of 405-line System A, 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, France abandoned it in favor of the Europe-wide standard of 625-lines, with the final 819-line transmissions from Paris in 1984. 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. They were switched to 625-lines in June 1981.

Multiple sub-nyquist sampling Encoding system (MUSE)

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 or 1125-lines 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.
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.
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 of the picture makeup as there are no other scanning lines, so NTSC's 525-lines become 480i, and MUSE would be 1035i.
Shadows and multipath still plague this analog frequency modulated transmission mode.
Considering the technological limitations of the time, MUSE was a very cleverly designed analog system.
Though Japan has since switched to a digital HDTV system based on ISDB, the original MUSE-based BS Satellite channel 9 was still being broadcast. It broadcast the same programs as BS-digital channel 103, but transmission ended on November 30, 2007.
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 for reference images, though 4:0.75:0.65 is probably typical for multi-channel delivery.

HD-MAC

HD-MAC was a proposed television standard by the European Commission in 1986 . It was an early attempt by the EEC to provide HDTV in Europe. It was a complex mix of analog signal multiplexed with digital sound. The video signal was encoded with a modified D2-MAC encoder.
In the 1992 Summer Olympics experimental HD-MAC broadcasting took place. 100 HD-MAC receivers in Europe were used to test the capabilities of the standard. This project was financed by the European Union. 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, which allows both SDTV and HDTV.