High Definition Video (HDTV)

Further confusing the issue are the 18 different digital television (DTV) standards currently recognized in the USA. Not all 18 are considered HD. Generally, only the wider 16:9 "film like" aspect ratios are considered to be HD, however you sometimes hear the 480p format described as HD as well.

How did we get to where we are? Video slowly developed from the experimental stages in 1897 up to experimental broadcasts in 1934, with 300 or less lines per image. The first NTSC standard was released in 1941 for black and white video with 483 visible lines. In 1949 the NTSC standard was revised for color video. In 1967 the PAL (Phase Alternation by Line) and the SECAM (Systeme Electronique Couleur Avec Memoire) standards were adopted in Europe.

The aspect ratio of the early NTSC standard matched that of 35mm film, or 4:3. In the 1950s movie makers began to experiment with wider aspect ratios (some say to compete with color television). The wider movie picture was intended to immerse the viewer in the picture by filling more of the field of view. Movies were still shot on film with a 4:3 aspect ratio, but cropping masks were used or special lenses were used on both cameras and projectors. Today all movies use the wider aspect ratio. In 1968 TV took the first steps needed to produce their own wide screen images, when the research arm of the Japanese national broadcaster, NHK, started development of a HDTV system (with 1125 lines at 60 fields/s). In 1981 Sony introduced the first High Definition Video System (HDVS).

In 1995 the ATSC (Advanced Television Systems Committee, a private sector organization) presented a standard for digital television transmission. This standard was adopted by the American FCC in December of 1996. It allows 18 different combinations of height and width and frame rate and type. The wide screen formats form the basis for the HD Video formats currently in use.

ATSC (Advanced Television Systems Committee)

The ATSC, a private sector organization, was formed in 1982 with about 25 corporate members. By 1984 it had grown to about 50 members. Membership increase rapidly when the ATSC opened membership to the world in 1996, making ATSC an international organization. In 2001 the ATSC had over 200 corporate members.

Note that the ATSC is an international private sector organization, not to be confused with the United States Federal Communications Commission's Advisory Committee on Advanced Television Service, established in 1987 to advise the FCC on technical and public policy issues regarding advanced television.

The ATSC was formed to develop voluntary standards for the entire spectrum of advanced television systems, including high-definition television. It presented a standard for digital television transmission in 1995. This standard was adopted by the FCC in December of 1996. This standard requires an information data transmission rate of 19.39 Mbits/s. The data rate of the digital TV signal is higher than that of just the information data transmission rate, as it contains digital error correction information as well. ATSC signals are still limited to a 6 MHz bandwidth, just like NTSC.

ASTC signals can have different aspect ratios (4:3 or 16:9) and different numbers of horizontal lines per frame. They can have different frame rates (24, 30 or 60 frames per second). They can be interlaced fields or progressively scanned frames. The audio is digital audio. The ATSC transmission standard is based on the MPEG-2 standard. The data is compressed, then transmitted to the TV, it is buffered, it's decoded, and then it is displayed. This means that when you switch channels there is a delay while new data is buffered before the picture can be displayed.

The ATSC Table 3, as adopted:

Vertical size	Horizontal size	Aspect ratio	Frame rate	Sequence
1080	1920	Square samples 16:9	23.976, 24, 29.97, 30 *	P
			29.97, 30	I
720	1280	Square samples 16:9	23.976, 24, 29.97, 30, 59.94, 60	P +
480	704	4:3 16:9	23.976, 24, 29.97, 30, 59.94, 60	P
			29.97, 30	I
	640	Square samples 4:3	23.976, 24, 29.97, 30, 59.94, 60	P
			29.97, 30	I

* 60 P is not available because the bandwidth would be too high

+ this resolution was developed for P only

Notes:

The audio data in an ATSC signal conforms to AC-3 audio (a system developed by Dolby Labs), which provides six channels of surround sound.

SQ = Square pixels (as opposed to rectangular pixels)

i = each frame is made up of 2 interlaced fields (e.g., line 1, 3, 5, etc. are drawn, then line 2, 4, 6, etc.)

p = each frame is one progressively scanned image (i.e., lines 1, 2, 3, 4, etc. are drawn top to bottom)

30i is often interchangeably referred to as 60i and 25i as 50i.

HD Standards

Developing standards for any industry can be a careful balancing act between technical requirements, political considerations, and the interests of the companies that are involved. Some of the groups that have been involved in defining HDTV have been the ATSC, the American FCC, SMPTE, the BTA of Japan (Broadcast Television Association) and the ITU.

ITU (International Telecommunication Union): ITU-R BT.601 format (includes the NTSC SD format)

SMPTE Standards that are relevant to HDTV:

SMPTE 240M – 1035 lines x 1920 active pixels; 16:9

SMPTE 259M – 525/625 or 480i60; SDI data rate: 270 Mbps

SMPTE 274M – 1080i 60 Hz format

SMPTE 292M – HD-SDI: 1080i60, 1080p24, 720p60; SDI data rate: 1.485 Gbps or 1.485/1001 Gbps

SMPTE 294M – 480p60; SDI data rate: 360 Mbps

SMPTE 295M – 1080i 50 Hz format

SMPTE 296M – 720p 60 Hz format

SMPTE 344M – SDI interface with data rate of 540 Mbps

High Definition Video: Comparison of some standards

Video

Standard	ITU-R 601	SMPTE 296M	SMPTE 274M	SMPTE 274M
Active pixels	486 x 720	720 x 1280	1080 x 1920	1080 x 1920
Total pixels*	525 x 858	750 x 1650	1125 x 2200	1125 x 2200
Pixel shape	rectangular	square	square	square
Active Pixels/frame	349,920	921,600	2,073,600	2,073,600
Bytes/pixel (4:2:2)	2	2	2	2
Frames/sec	29.97	59.94	24	29.97
Interlaced or Progressive	Interlaced	Progressive	Progressive	Interlaced
Bytes/sec	20,974,226	110,481,518	99,532,800	124,291,708
Active information (MB/s)	20.00	105.4	94.92	118.5
Total information (MB/s)	25.75	141.5	113.3	141.5
Total information (Gb/s)	0.201	1.11	0.885	1.11

Audio

Audio sample rate	48,000 Hz	48,000 Hz	48,000 Hz	48,000 Hz
Bits/sample	16	16 - 24	16 - 24	16 - 24
Channels	2 (stereo)	AC-3 audio: 5.1 channels of surround sound	AC-3 audio: 5.1 channels of surround sound	AC-3 audio: 5.1 channels of surround sound
Audio bits/sec	1,536,000	640,000 max.	640,000 max.	640,000 max.
Audio Bytes/sec	192,000	80,000 max.	80,000 max.	80,000 max.

HDTV Transmision

Bandwidth	6 MHz	6 MHz	6 MHz	6 MHz
Data rate throughput (Mb/s)	N/A	19 (terrestrial) 38 (cable)	19 (terrestrial) 38 (cable)	19 (terrestrial) 38 (cable)
Compression (video)	Analog, uncompressed	MPEG-2	MPEG-2	MPEG-2
SDI / HD-SDI Data Rates	270 Mb/s	1.485 Gb/s	1.485 Gb/s	1.485 Gb/s

* Includes samples in the horizontal and vertical blanking interval

Sampling Rate: Is it 4:2:2 or 22:11:11 for HD?

Digital video (and audio) uses digital sampling to collect data. At regular intervals the signal is measured, or sampled. The sampling rate is also referred to as the frequency, or cycles per second, or Hz. For example, for a CD the audio signal is measured 44,100 times per second or 44.1 kHz. In general, when sampling a signal the sampling rate must be at least double the highest frequency found within the signal to avoid missing high frequency (short duration) signals. Higher sampling rates are generally preferred, but higher rates result in an increase in the amount of data generated.

SD Sampling

In the early days of SD digital video a sampling rate of four times the NTSC color subcarrier (3.58 MHz x 4 = 14.3 MHz) was used to sample composite NTSC video. A slightly higher rate of 17.7 MHz was used for PAL. Eventually both NTSC and PAL video settled on a sampling rate of 13.5 MHz (approximately four times the frequency of the subcarrier, or 4fsc).

A component video signal has a luminance (Y) and two color difference (R-Y and B-Y) signals. A component digital signal that samples all 3 components at 13.5 MHz is referred to as a 4:4:4 signal (where the first 4 is for the luminance and the next two 4s are for the color information). Sometimes you will see a digital signal referred to as a 4:2:2 signal. The "4" represents the luminance sampled at 13.5 MHz. The "2" is used to represent a signal sampled at 6.75 MHz (½ of 13.5 MHz). Some digital signals may be a 4:1:1 signal, where the "1" is used to represent a signal sampled at 3.375 MHz (¼ of 13.5 MHz). Sometimes you will see a digital signal with a 4:2:2:4 signal. The fourth 4 represents the sampling of the alpha channel signal. Digital signals sampled at 4:2:0 sample the Y at 13.5 MHz, and the R-Y and B-Y at 6.75 MHz every other line (one line is sampled at 4:0:0, Y only, and the next line is sampled at 4:2:2).

The ITU-R 601 standard specifies 4:2:2 sampling for digital studio equipment. Digital signals that are sampled at 4:2:2 sample the color difference only half as often as the luminance. The eye is less sensitive to color sharpness than to luminance sharpness, so reducing the data rate by reducing the color sampling rate makes sense. Professional SD DV camcorders with 4:2:2 sampling take what amounts to 720:360:360 pixels per scanline.

DV camcorders with a data rate of 25 Mbps sample signals at 4:1:1. Digital signals sampled at 4:1:1 sample the Y at 13.5 MHz, and the R-Y and B-Y at 3.75 MHz. A home DV camcorder uses 4:1:1 sampling, which amounts to 720:180:180 pixels per scanline.

HD Sampling

According to the ATSC, HD is sampled at 74.25 MHz, whether the format is 1080i, 1035i, or 720p, yielding 1920 pixels for luminance per line.

People sometimes speak of HD cameras using a sampling scheme of 4:2:2 (four Y samples, two Pr samples, and two Pb samples), but these numbers are misleading because the "4" represents a larger number in the HD world (74.25 MHz) than in the SD world (13.5 MHz). In the HD world, 4:2:2 would mean 1920:960:960 pixels. The ATSC uses the numbers 22:11:11 to more precisely describe the "4:2:2" HD sampling scheme (because for SD 1 = 3.375 and 22 x 3.375 = 74.25). However, the more familiar (if less precise) 4:2:2 is still commonly used when referring to HD signals. In terms of pixels, the numbers for 3:1:1 HD (the Sony HDCAM format) would be 1440:480:480. While 3:1:1 seems low, it still is significantly more samples than the 720:360:360 pixels of SD's 4:2:2 sampling.

SDI and SDTI Data

The SDI (Serial Digital Interface, SMPTE 259M) transmits uncompressed standard definition video. The data is coded into a 270 Mb/s serial data stream (originally designed for for 10-bit 4:2:2 YUV data at 27 MHz) or a 360 Mb/s serial data stream (originally designed for composite data with an 8 x PAL subcarrier sample rate of approximately 36 MHz). There is also a new 540 Mbps SDI (SMPTE 344M) which was designed for 480P video data streams.

An uncompressed digital studio HDTV signal requires a transmission rate of 1.485 Gb/s (for 1125-line, 2:1 interlace, 10-bit component sampling). The active payload is approximately 1.2 Gb/s (for 1035/1080 active lines). The uncompressed HD-SDI system is described in SMPTE 292M.

SDI signals are intended to carry video and audio data in a specific format. In order to carry a wider range of data types SDTI (Serial Data Transport Interface) signals were developed. SDTI builds on the SDI standard. SDTI signals are similar to SDI signals. However, in an SDTI signal the portion of the signal that would normally carry the video data in an SDI signal is replaced with an "opaque" data stream. This allows SDTI to transport "packetized" audio, video and data.

Since SDTI signals can carry any data type it can be used to carry compressed HD data. For example, Sony HDCAM VTRs have optional SDTI boards that can be used to transmit the Sony HDCAM data in an SDTI 270 Mb/s data stream.

SDI and SDTI data streams can use the same hardware. For both SDI and SDTI, for a 270 Mb/s data stream there is a 200 Mb/s payload (or for SDTI the active portion of each video line is 1440 words). For a 360 Mb/s data stream there is a 270 Mb/s of payload (or for SDTI the active portion of each video line is 1920 words).

Uncompressed and Compressed HD Formats

An uncompressed HD digital tape recorder must have the capacity to record at a rate of approximately 1.2 Gbits/s (or 150 MB/s). The 19 mm D-6 digital 1 Gb/s recording format can be used to record uncompressed HD footage (SMPTE 277).

There are very few uncompressed HD VTRs available today. In 1993 the BTS company introduced the first full-bandwidth HDTV recorder to use a cassette tape format, the DCR-6000. Philips later aquired BTS and re-developed this VTR with Toshiba to produce the Voodoo HDTV Cassette Recorder. The Voodoo uses the D-6 format. (Philips and the Voodoo are now owned by Thompson Multimedia Broadcast and Network Solutions.) This recorder samples at 8 bits/pixel, using 4:2:2 sampling, along with 10 channels of audio. This sampling rate results in a data rate of just over 1 Gb/s.

Sony also manufactured an uncompressed HD VTR, the HDD-1000, however it is no longer being manufactured.

Uncompressed HD video recorders are expensive, typically costing approximately $400,000 USD.

A video recorder that can record an picture with 4:1 compression (Panasonic D5 format) or 6:1 compression (Sony HDCAM) costs less than $100,000 USD. Even though a 6:1 compression may seem high for standard definition video, for HD video it results in a clean image with almost no visible digital artifacts.

Sony, Panasonic and JVC Compressed HD Formats

Sony's HDCAM format uses a proprietary compression technology "derived from DV and with certain similarities", but not part of the DV family. It uses a data rate of 135 Mb/s.

Both JVC and Panasonic have 100 Mb/s DV-derived products. These products gang four DV codecs together to get the 100 Mb/s data stream. Panasonic calls their product DVCPROHD (or sometimes D7 HD). JVC calls their product D9 HD.

DVCPROHD and D9 HD both record 1280 Y samples and 640 Cr & Cb samples per line, compared to HDCAM's 1440 Y and 480 Cr & Cb samples. Thus the DVCPROHD and D9 HD formats have slightly lower luma resolution than HDCAM but slightly better chroma resolution.

Panasonic also manufactures a switchable 720p/1080i D5 HD VTR (which is not based on DV technology), the AJ-HD2700, which has become a popular studio VTR in the USA.

HD Formats compared by Product

Panasonic DVCPRO P	Panasonic DVCPRO HD (D7-HD)	Panasonic D5 HD	JVC D9 HD	Sony HDCAM	Sony HDD-1000 Discontinued	Philips/ Toshiba D6 (Voodoo)*
480p	1080i,1035i	1080i, 720p, 1080p24	1080i, 720p, 1080p24	1080i, 1080p24, opt. 720p	1125i	1080i, 1080p24
50 Mb/s	100 Mb/s	235 Mb/s	100 Mb/s	135 Mb/s	1.2 Gb/s	1.5 Gb/s
4:2:0	15:7:7 Y = 1280 C = 640	22:11:11 Y = 1920 C = 960	15:7:7 Y = 1280 C = 640	17:6:6 Y = 1440 C = 480	22:11:11 Y = 1920 C = 960	22:11:11 Y = 1920 C = 960
	Up to 6.7:1	4:1 (8 bit) or 5:1 (10 bit)	6.6:1 (8 bit)	Filtering, then 4.4:1; or 7:1 (8 bit data, 10 bit I/O)	uncompressed	uncompressed (10 bit for Y, 8 bit for C)

* Now owned by Thompson Multimedia Broadcast and Network Solutions

Other interesting numbers:

Many digital-cinema projectors fill the screen with just 1280 pixels. Note that 1280 is the number of pixels across in the 720p standard.

Most HDTV equipment has 1125 total scanning lines, with 1080 as the picture lines. However, the Japanese NHK system with 1125 scanning lines typically has 1035 picture lines.

NHK did some tests that suggested that 731 progressive scanning lines offered equivalent vertical perceptual resolution to 1125 interlaced lines. Thus today's 720p could offer more vertical detail than 10801i.

Cables and Connections for HD

When hooking up an HD-SDI signal to an HD monitor, HDTV or HD projector you may run into some unfamiliar cables.

Most HD monitors will not have an HD-SDI in. Normally you will have to convert the HD-SDI digital signal into an analog signal. Several companies manufacture these HD-SDI to analog HD converters (Leitch, AJA and Evertz are three examples).

An analog HD signal may use a common 3-ended BNC YUV or RGB cable which carries the sync signal on one of the color cables, usually the green (called RGB sync on green). You may also see a 5-ended video cable with RGBHV. This cable splits the video into red, green, blue, horizontal sync and vertical sync. There are also some 4-ended video cables with RGV H/V, which carries both the horizontal and vertical sync on a single H/V cable.

RGBHV connectors are found on most high-end professional monitors and on the most popular HDTV decoder (by RCA). An RGBHV signal is also the way a computer connects to a projector. Five pins on a 15-pin VGA cable are RGBHV. The projector recognizes the type of signal and projects accordingly. Note that RCA has chosen to send the HDTV signal via a 15-pin VGA cable instead of via a component connection. The standard connection for HDTV tuners has yet to be decided.

Cable Attenuation (or Loss)

The most important characteristic to consider when selecting a coaxial cable for SDI or SDTI data transmission is attenuation. Generally there is some signal loss, and the longer the cable the more signal loss occurs. This loss is generally referred to in dB. The signal loss is also different for different signal frequencies. Generally, the higher the frequency, the higher the signal loss over the same length of cable.

For SDI and SDTI signals the frequency of the signal in MHz is effectively the same as the bit rate. For HD SDI running at 1.5 Gbps, SMPTE 292M governs cable loss calculations. In the SMPTE 292M standard, the maximum cable length would have no more than a 20 dB loss at one-half the clock frequency (or a frequency of 740 MHz).

As an example, for Belden 1694A cable, the cable's specs are 5 dB per 100 feet at 740 MHz. Note that the loss in dB is given per cable length at a specific frequency.

Film Frame Sizes (for reference)

The visible area of an NTSC frame is 720 x 486 pixels, and of a PAL frame is 720 x 576 pixels.

To store a computer image that has the equivalent resolution of a 35 mm film image it needs to be stored at a resolution of 5000 x 3760 pixels. However, images are rarely stored at this high resolution. The threshold of human vision when viewing an average movie theater screen is about 2500 pixels in width, so working with an image that is 5000 pixels wide is a bit of overkill.

When film frames are stored as a computer image file three common pixel dimensions are used - 2K, 3K or 4K. A 2K image has a width of 2000 pixels, a 3K image has a width of 3000 pixels, and a 4K image has a width of 4000 pixels. The height varies depending on the aspect ratio of the original film. Working with 3K or 4K is common.

Notes on Aspect Ratios

The actual aspect ratio of 35 mm film is 1.33:1 (or 4:3). This exact ratio was used for most silent pictures, but Hollywood changed the picture ratio slightly with the advent of talkies, to make room for an audio track. The new ratio, 1.37:1, became known as the Academy Ratio and was used for the vast majority of U.S. films until the 1950s.

In the 1950s, movie-makers began developing techniques to widen the aspect ratio of their movies. The wider picture filled more of the audience's natural field of vision, which has more width than it does height because our eyes are positioned side by side. The movie industry believed that the wider picture would immerse the viewer more deeply in the world of the movie than the smaller television set picture.

Since the 1960s, almost all major filmmakers have used a wide aspect ratio when making a theatrical movie. The aspect ratio used by the various studios varied from about 1.5:1 up to the common 1.85:1.

Movie makers still use 35 mm film with a 1.37:1 aspect ratio, however, so they have to somehow impose another aspect ratio on that film. Today, the most common methods of imposing a wide aspect ratio are using an anamorphic lens, hard matting and soft matting.

A Brief History of Television

When experimental television broadcasts first started in 1925 there was no standard resolution (and no need for standards). Things have changed.

1897: Karl Ferdinand Braun, a German physicist, invents the first cathode-ray tube, the basis of all modern television cameras and receivers.

1919: The Radio Corporation of America (RCA) is formed.

1923: Vladimir Zworykin, while working for Westinghouse, applied for a patent for the "Iconoscope". The patent was not granted. Later, while Zworykin was working for RCA, this failed patent application became the basis of an on-going battle between RCA and Philo Farnsworth (see 1927).

1926: John Logie Baird was a British inventor of a mechanical video system which he used to first successfully transmit an image from one room to another in 1926. Baird's system was able to transmit about 60 lines per frame. During the early 1930s the BBC allowed John Logie Baird to use their radio channels to broadcast pictures on an experimental basic. By 1934 Baird had sold more than 20,000 Televisor receivers all over Europe.

1926: Warner Bros. Premiered Don Juan, the first full length film with a synchronized sound track of music and audio effects. This sound was recorded on a disk and played along with the film.

1927: On January 7th, 1927 Philo Farnsworth applied for a patent for his electronic Television system (1,773,980) and Television receiver (1,773,981), including his "Image Dissector". It was issued in August 1930.

1928: In 1928 Hungarian Kálmán (Coloman) Tihanyi was the first to successfully patent the concept of a light-sensitive image storage tube (an iconoscope). US patents assigned to RCA were issued to Tihanyi in 1938-39 with 1928 priority.

1928: Disney's first sound film, Steamboat Willie, featured a fully-synchronized soundtrack of music and sound effects and dialogue, recorded optically as sound-on-film.

A note on aspect ratios: The actual aspect ratio of 35 mm film is 1.33:1 (or 4:3). This exact ratio was used for most silent pictures, but Hollywood changed the picture ratio slightly with the advent of talkies, to make room for an audio track. The new ratio, 1.37:1, became known as the Academy Ratio and was used for the vast majority of U.S. films until the 1950s.

1934: Baird met with Farnsworth in the fall of 1934. At a demonstration in Britain, Philo Farnsworth was able to transmit an image that was composed of more than 300 lines per frame.

1934: After returning from Britain Farnsworth set out to build a television studio. They started by building 2 Image Dissector cameras with a resolution of 441 lines per frame. They built a transmission tower that could blanket Philadelphia's metropolitan area. They also built the world's first electronic video switcher, to allow them to cut between their 2 camera. The FCC granted Farnsworth a license to conduct experimental television transmission under the call letters W3XPF. Fewer than 50 homes in Philadelphia were equipped with video receivers.

1935: AT&T staked out its claim in 1935, when Bell Labs introduced a wired solution to the problem of sending television transmission from city to city. Their invention was called a "coaxial cable" owing to the fact that one conductor was threaded through the center of a flexible copper tube. With this development, AT&T placed itself in perfect position to give itself the job of wiring together television networks. The FCC tentatively gave AT&T permission to experiment with their cable, and one was strung almost immediately from New York to Philadelphia to begin testing. In the meantime, the FCC opened an inquiry to make certain that AT&T was not about to create another communications monopoly.

1936: In 1936 Britain adopted a monochrome 405 line standard for television broadcast. (In 1967, when the PAL color standard was introduced with 625 lines, 576 with visible picture information, the 2 standards operated in parallel. In 1986 the 405 line service was terminated.)

1938: After many modifications of his 1923 patent, a patent was finally issued to Vladimir Zworykin, then working for RCA, for a "Cathode ray tube, Television" (2,139,296) after a court of appeals ruled in Zworykin's (and RCA's) favor. He was issued a second, related patent in August 1939 (2,168,892).

1939: In 1939 David Sarnoff of RCA finally stopped fighting with Farnsworth and agreed to pay royalties to an independent inventor for the first time in RCA's history.

1939: At the 1939 World's Fair in New York Roosevelt became the first American President to appear on television. Later that week television receivers went on sale at a few stores in New York. These first commercial sets used a 441 line/30 frame standard.

1940: In 1940 the American Federal Communications Authority (FCC) announced that permission to broadcast commercially was rescinded until the establishment of a standard system. This led to the establishment of the NTSC (National Television System Committee). The first NTSC had 168 committee and panel members. It finished its work in March 1941.

1941: In 1941 the American Federal Communications Authority (FCC) set the standards for a 525 line (483 with visible picture information) black and white TV transmission.

1949: In 1949 the NTSC was reconvened for the second time to set standards for color TV. This time, 315 people met. In March 1953 the NTSC color television broadcast system was presented. In December of 1953 the FCC authorized their use. It specifies a fixed vertical resolution of 525 horizontal lines, 483 of which carry the picture information, and the equivalent amount of time it would take to draw 21 lines for the vertical blanking interval (VBI) for each of the 2 fields. There are 59.94 interlaced fields displayed per second (for 29.97 frames per second). It used a 6 MHz channel.

1950s: In the 1950s, movie-makers began developing techniques to widen the aspect ratio of their movies. The main thing movie theaters had over television sets is that they could immerse the viewer more deeply in the world of the movie, and the best way to do this was to fill more of the audience's natural field of vision (which has more width than it does height because our eyes are positioned side by side).

1952: The first wide screen film, This Is Cinerama was produced by Cinerama. It used 3 side-by-side 35mm images to display its wide screen image.

1953: Paramount entered the wide screen format competition with its release of Shane, a film that used a 1.66:1 aspect ratio. 20th Century-Fox introduced CinemaScope. Metro-Goldwyn-Mayer and Disney adopted a cropped aspect ratio of 1.75:1. Universal-International and Columbia Pictures determined that they could get by with cropping to an aspect ratio of 1.85:1.

Since the 1960s, almost all major filmmakers have used a wide aspect ratio when making a theatrical movie. The aspect ratio used by the various studios varied from about 1.5:1 up to the common 1.85:1.

1967: The PAL (Phase Alternation by Line) standard was adopted in 1967. It has a vertical resolution of 625 horizontal lines (with 576 visible picture carrying lines). There are 50 interlaced fields displayed per second (for 25 frames per second). In Britain this standard ran in parallel with the monochrome 405 line standard for television broadcast (adopted in 1936) until 1986.

1967: The SECAM (Systeme Electronique Couleur Avec Memoire) standard was adopted in 1967. It has a vertical resolution of 625 horizontal lines (with 576 visible picture carrying lines). There are 50 interlaced fields displayed per second (for 25 frames per second).

1970s: The NHK Hi-vision, a HDTV system with 1125 scanning lines, transmitted at 60 interlaced fields per second, was developed by the Japanese national broadcaster and Sony.

1981: Sony introduced the High Definition Video System (HDVS). In 1984 Sony introduced the first analog HD 1-inch VTR. In 1989 Sony introduced the first digital HD VTR, which also used a 1-inch tape. In 1997 Sony introduced the first one-piece HD camcorder and its associated editing VTR.

1982: The ATSC (Advanced Television Systems Committee), a private sector organization, was formed with about 25 corporate members. (The ATSC currently has over 200 corporate members.)

1995: The ATSC presented a standard for digital television transmission in 1995. This standard was adopted by the FCC in December of 1996. It allows 18 different combinations of height and width and frame rate and type.