UNIT 21: UNDERSTAND

ING VIDEO TECHNOLOGY

U 2 1 A 1 : V I D E O R E C O R D I N G , E D I T I N G A N D B R OA D C A S T T E C H N O LO G Y

GRADING CRITERIA FOR U21A1 REPORT:P1 - describe the principles of digital video technology and digital video recording with some appropriate use of subject terminology• Give definitions of all of the terms covered in this presentationM1 - explain the principles of digital video technology and digital video recording with reference to detailed illustrative examples and with generally correct use of subject terminology• Find examples (pictures) that are relevant to the definitionsD1 - comprehensively explain the principles of digital video technology and digital video recording with elucidated examples and consistently using subject terminology correctly• Use secondary sources of information (quotes/articles/screenshots from films) to support

what you are writing about

TELEVISION STANDARDS AND CONNECTION SYSTEMSa) The RGB system

- This is the standard colour system used in TV & Film- The primary additive colours are Red, Green & Blue- The human eye sees all colours as a combination of these colours- The secondary additive colours are Yellow, Cyan and Magenta- Televisions and computers display all colours as a combination of these colours

- Cameras covert these colours

TELEVISION STANDARDS AND CONNECTION SYSTEMSb) TV Standards The following are colour encoding systems for analogue television- PAL – Phase Alternative Line – was used in the UK and parts of Europe- NTSC – was used in the US- SECAM – was used in FranceThe following are colour encoding systems for digital television- DVB – Digital Video Broadcast – used in the UK and many other companies- DTMB - Digital Terrestrial Multimedia Broadcast – used in China- ISDB - Integrated Services Digital Broadcasting - used in Japan

TELEVISION STANDARDS AND CONNECTION SYSTEMSTwo methods used for "painting" an image on a television screen:• Interlace (for example 1080i)

– PAL – scans 50 lines per second (25 odd, 25 even)– Needs to be de-interlaced by televisions and computer monitors– Can create ‘artefacts’.– Signal bandwidth – cheaper as it requires less bandwidth

• Progressive (for example 720p)– All lines are drawn in sequence– Requires more bandwidth

TELEVISION STANDARDS AND CONNECTION SYSTEMSc) HDTV – High Definition TV

– 1080 lines at 30 frames per second (FPS)– A lot higher and faster than the analogue TV Signal which was 625 lines at 25

FPS– This faster refresh rate of the frames means that the resolution is much higher

d) Aspect Ratio – to do with the width and height of the image– TV and films were traditionally 4:3– Screens with greater width are widescreen – 16:9– Examples are on the next slide

TELEVISION STANDARDS AND CONNECTION SYSTEMSe) Connection Systems:

– Phono Connections have one video line and two audio lines– SCART connections separate luminescence (brightness) and Chrominance

(colour RGB)– Serial/Parallel Port connections are used in digital systems/computers

• Please research the following and explain where they may be used – also look at USB & Firewire

BROADCAST SYSTEMS

A) Terrestrial Broadcasting– The transmission of a TV signal without it leaving the earth’s atmosphere

BROADCAST SYSTEMS

B) Satellite Broadcasting– The transmission of a TV signal which leaves the earths atmosphere and is

beamed back to the earth via satellite

BROADCAST SYSTEMS

C) Multiplexes– Technology that enables several signals to be transmitted at the same time

along the same path – e.g. multichannel television

PRODUCING IMAGES AND SOUND

PRODUCING IMAGES AND SOUND• How images are produced

– Light passes through the camera lens – The image is focussed on the prism– The light is split into its 3 primary colours– The 3 beams of light pass to 3 Charge Coupled Devices (CCDs) or image sensors– The CCDs transform the light into electrical signals– These signals are then converted through a series of microchips into a digital

image– This digital image is then stored (usually on an SD Card)– The amount of light that reaches the CCDs is determined by the Shutter Speed

and Iris Aperture

PRODUCING IMAGES AND SOUND• The Iris

– Can be opened up or closed down– Smaller aperture = less light– Larger aperture = more light

PRODUCING IMAGES AND SOUND• Shutter Speed

– This is the amount of time that light is processed for each frame• Slow shutter speed = more light• Fast shutter speed = less light

PRODUCING IMAGES AND SOUND• White Balance

– a control on the camera that compensates for the colour effect of day light (blue) and artificial light (yellow)

– Different light has different temperatures and will look different on camera

– White balance compensates for this change in temperature/light

PRODUCING IMAGES AND SOUND• Focus

– Focus is adjusted by changing the position of the lens in relation to the prism

– This helps to sharpen or blur the image

PRODUCING IMAGES AND SOUND• Microphones

– How sound is produced• The head of the microphone vibrates a diaphragm around a magnet when it picks up

sound waves• This produces and electrical signal in the coil