Introduction Video Basics (Analog Systems) Transmission Systems Wireless (terrestrial) Wired (cable television) Digital Video (Two Weeks)
Video Standards Standards and Principals –Persistence of Vision The rapid presentation of frames of video information to give you the illusion of smooth motion.
Frequency Standards Frame Frequency 16 Frames per Second (fps) Black and White 24 fps SOF Continuity of Action Problem of Flicker –The gross alteration of light and dark
Frequency Standards Field Frequency Frame Frequency x 2 Continuity of Illumination
Film Vs. Video Film - Project a complete picture Video - Scan, line by line, at a high rate of speed - 6 million bits per second
How do we describe a picture? A picture element (pel or pixel) one at a time For each pel we need to somehow describe: –Brightness (luminance) –Hue (phase, tint) –Saturation (color intensity, chroma)
Vertical Resolution The picture quality associated with the number of dots (pixels) used to construct the picture. – 367,000 dots – on 525 rows (vertical)
Vertical Blanking Interval (VBI) Lines 1-21 of each field Vertical Interval Test Signal (VITS) Vertical Interval Reference Signal (VIRS) Lines 1-9V-sync and Equalizing Pulses Lines 12-14SMPTE Time Code Lines 17-19VITS and VIRS Line 20Network Source Code (field 1) Line 21 Closed captioning (field 1)
Kell Factor The Ratio of effective resolution to the theoretical resolution is known as the Kell Factor.
Vertical Resolution Summary Max Lines/Frame = 525 Lost for Vertical Blanking = 42 (21 lines per field) Visible = 525-42 = 483 Kell Factor = 72.5% Effective Resolution = 350 lines
Horizontal Resolution Summary (4.2 MHz Video Bandwidth) = 4.2 cycles per microsecond x 52 microseconds (active scan) x 2 pixels per cycle = 436 pixels per line
Television Transmission Picture Information Blanking pulses Sync pulses Audio information
Direct Waves The primary path of the direct wave is from the transmitting antenna to the receiving antenna. So, the receiving antenna must be located within the radio horizon of the transmitting antenna. Because direct waves are refracted slightly, even when propagated through the troposphere, the radio horizon is actually about one-third farther than the line-of-sight or natural horizon.
Ground Waves The Earth has one refractive index and the atmosphere has another, thus constituting an interface that supports surface wave transmission. These refractive indices are subject to spatial and temporal changes.