Dr. Wes Leggett Television Basics

Television and Videotape Format Basics
Dr. Wes Leggett

NTSC vs. ATSC

National Television Standards Committee - 1940's
Analog Broadcast Standard:
525 Total Horizontal Scan Lines - Interlaced - 1/60sec Odd Lines (Field) plus 1/60sec Even Lines (Field) equals 1/30sec Frame (30fps)
480 Actual Displayed Horizontal Scan Lines, remaining non-displayed lines reserved for sync signals
720 Maximum Horizontal Pixels (Left to Right - Vertical Resolution)
330 Actual Displayed Horizontal Pixels (Back in the 1940's and 50's it was both cheaper to manufacture broadcasting equipment and televisions that only displayed 330 pixels, so why spend the money to broadcast and receive and display more than 330? The 330 pixel benchmark has carried forward through the years and is still in use today by some local broadcasters and inexpensive televisions.)
720x480 Maximum Broadcast/Displayed Resolution
330x480 Typical Displayed Resolution

NTSC Standards added in later years:
Color Broadcasting - Red, Green, and Blue "guns"
2 Channel Sound - Stereo Left and Right

Advanced Television Standards Committee - 1980's
Digital Broadcast Standard:
1125 Total Horizontal Scan Lines
1080 Actual Displayed Horizontal Scan Lines, remaining non-displayed lines reserved for sync signals
1920 Maximum Horizontal Pixels (Left to Right - Vertical Resolution)
1920x1080 Maximum Broadcast/Displayed Resolution
By 2006, all television stations must broadcast in Digital
5.1 Channel Sound - Front Left, Front Center, Front Right, Rear Left, Rear Right, Bass (.1)

HDTV Formats:
1. 480i (interlaced) - 720x480 Display Resolution - able to display NTSC Analog Broadcast Signal
2. 480p (progressive scan) - 720x480 Display Resolution - non-interlaced - 1/60sec All Lines plus 1/60sec All Lines equals 1/30sec Frame
3. 720p (progressive scan) - 1280x720 Display Resolution - non-interlaced
4. 1080i (interlaced) - 1920x1080 Display Resolution

Question: How do all these new higher resolutions fit into the 6 MHz bandwidth of NTSC?
Answer: MPEG-2 Compression, 55 to 1 on average.

4:3 vs. 16:9

W. Dickson in 1889, working for Thomas Edison Labs in developing the Kinescope, used film that was 1" x 3/4", thus the 4:3 Aspect Ratio was born! In the 1950's, when televisions were selling like hotcakes, Cinemascope (16:9) was developed in Hollywood to give audiences a different viewing experience than the 4:3 "box" at home and a reason to pay to go see the movies. The 16:9 Aspect Ratio more accurately reflects our human field of vision.

Sony vs. JVC "The Videotape Format War"

1. Sony introduces Beta, a new consumer videotape format for the home.
2. JVC introduces VHS (240x480), and by selling it for less than it costs to produce, JVC monopolizes market share.
3. Sony introduces 8mm (270x480), whose tape width is half the size of VHS (accomplished by combining the audio, video, and control tracks), yet still records 2 hours per tape like VHS, but whose cassette size is 1/4 the size of VHS cassettes, perfect for smaller and lighter hand-held camcorders.
4. JVC introduces VHS-C "Compact" (240x480), whose cassette is nearly as small as 8mm, but can only record 30, 60, or 90 minutes, depending on selected tape speed (SP "Standard Play", LP "Long Play", or EP "Extended Play"/SLP "Super Long Play"). By using a cassette adaptor, a VHS camcorder or VCR can playback a VHS-C cassette.
5. Sony introduces Hi8 (400x480), significantly increasing resolution, especially for editing purposes. A Hi8 camcorder or VCR can also playback tapes recorded in 8mm format
6. JVC introduces S-VHS "Super VHS" and S-VHS-C (400x480), matching Hi8's resolution. An S-VHS/S-VHS-C camcorder or VCR can also playback tapes recorded in VHS/VHS-C format. Format becomes popular with editors, because unlike the 8mm and Hi8 formats, having separate audio and video tracks allows independent audio dubbing and video dubbing to the original tape.
7. Sony introduces D8 "Digital 8" (500x480), which records on Hi8 cassettes, but at twice the speed, so recording time is only 60 minutes instead of 2 hours. A D8 camcorder can also playback tapes recorded in the Hi8 and 8mm format.
8. JVC introduces Mini DV (500x480), whose cassette size is 2/3 the size of Hi8 cassettes. Recording time is 30 or 60 minutes, depending on cassette used.
9. Sony introduces MICRO MV (500x480), whose cassette is 1/2 the size of Mini DV cassettes. Recording time is 30 or 60 minutes, depending on cassette used.

Video Cables

Coax - Video and Audio signals both carried in same cable.
Composite - Video signal carried in individual cable (Yellow RCA connector plug).
Separate "S-Video" - Video signals carried in individual cable, but separated into Luminance (brightness) and Chrominance (Color).
Component - Video signals separated into Red, Green, and Blue and carried in three individual cables.