mdia 308

MDIA 308

Television

TelevisionTelevision

• Like film – television is actually a series of Like film – television is actually a series of still images presented to the eye in rapid still images presented to the eye in rapid successionsuccession

• Earliest experiments in 1890sEarliest experiments in 1890s– Italian monk – Italian monk – CasselliCasselli– Pictures by wirePictures by wire

TelevisionTelevision

• Mechanical TelevisionMechanical Television

• Paul Nipkow – scanning diskPaul Nipkow – scanning disk– Nipkow diskNipkow disk

• John Loge BairdJohn Loge Baird– Scottish inventor working with BBCScottish inventor working with BBC– Launched the first system based on Launched the first system based on

mechanical scanningmechanical scanning

Nipkow diskNipkow disk

TelevisionTelevision

• Electronic television – cathode ray tubeElectronic television – cathode ray tube

• Vladimir ZworykinVladimir Zworykin– IconoscopeIconoscope

• Philo T. FarnsworthPhilo T. Farnsworth– Image DissectorImage Dissector

TelevisionTelevision

Electronic scanning

White lightBeam splitterBeam splitter

Cathode ray tube

White lightBeam splitterBeam splitter

Color TV screens

Television standards

• National Television Standard Commission (NTSC)

• Standard Definition (SDTV)• 4:3 aspect ratio• 525 lines of horizontal resolution• 30 frames per second• 60 fields per second• 2 fields per frame• Interlace scanning

Television standards

• High definition (HDTV)

• 16:9 aspect ratio

• 1080 lines of horizontal resolution

• 30 frames per second

• Progressive scanning

Magnetic tape recording

• Magnetic recording heads are transducers that convert electrical energy into magnetic

• Recording heads are electromagnets

• Audio current creates an alternating magnetic field

• The magnetic field is focused at the “gap” in the record head

Magnetic tape recording

Magnetic tape recording

• The fluctuations in the magnetic field are stored on tape by re-arranging the magnetic polarity of the “metal” surface of the tape

• The tape surface is made from powdered metals, like FeO2, or iron oxide (rust)

• The metals are attached to a plastic backing with binder (glue)

Magnetic tape recording

• Playback heads are constructed in a nearly identical manner

• During playback, a current is induced to flow in the coil of the head by the magnetic charges of the tape surface

Fundamentals of Audio Production. Chapter 6.

17

Analog tape recordingReel to reel

Videotape

• Ampex corporation invented the videotape recorder

• Allowed television programs to be recorded and “mistakes” could be corrected

Quadruplex Videotape

Quadruplex

Helical scan

Helical scan