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Description
The programme demonstrates properties of colour as used in t.v. systems and explains the method of encoding colour information in a t.v. signal. Representations of colour signals in terms of phasor...s are shown.
The programme demonstrates properties of colour as used in t.v. systems and explains the method of encoding colour information in a t.v. signal. Representations of colour signals in terms of phasor...s are shown.
| Module code and title: | T321, Telecommunication systems |
|---|---|
| Item code: | T321; 13 |
| First transmission date: | 21-08-1976 |
| Published: | 1976 |
| Rights Statement: | |
| Restrictions on use: | |
| Duration: | 00:23:00 |
| + Show more... | |
| Producer: | David Saunders |
| Contributors: | Chris Pinches; Gaby Smol |
| Publisher: | BBC Open University |
| Keyword(s): | BBC; Colour information; Colour triangle; Electronic formation; Engineering Training Centre; Hues; Phasor diagrams; Saturation; Television systems; Test signal |
| Footage description: | Gaby Smol introduces the programme. Smol displays the three primary colours in turn on the TV screen and demonstrates changes in luminance. He combines blue with red and then adds green to build a colour triangle. Smol discusses the colour characteristics of a colour triangle in terms of hue and saturation. He defines these terms before going on to discuss colour changes in terms of vectors. Chris Pinches, at the BBC Training Centre, Wood Norton, displays the colour signals which make up a colour bar pattern on an oscilloscope. He adds these three traces then expands the luminance signal in order to examine it in more detail. Pinches next explains how the chrominance signal is built up. He displays this signal on the oscilloscope and then adds it to the luminance signal to show a colour transmission signal. Pinches explains the need for a synchronisation pulse and colour burst pulse to complete a composite transmission signal which is suitable for applying to a synchronous demodulator in a t.v. receiver. He displays these on the oscilloscope. Gaby Smol, using animated diagrams, explains how the three signals (luminance and two colour difference signals) are combined in the NTSC system in such a way that they can be separated out again at the receiver. Smol displays two sinusoidal signals on the oscilloscope. One represents a modulated colour subcarrier corresponding to a region of uniform colour in the picture and the other the reference signal. He explains how difficult it would be to work out colour changes from these signals. Smol explains the advantages of using phasors to represent the signals. He displays phasors for several colours on the oscilloscope. The screen is surrounded by colours which represent the phasors being displayed. Smol points out the effects of saturation and hue errors in the system. His face changes colour to demonstrate. |
| Master spool number: | 6HT/72118 |
| Production number: | 00525_5232 |
| Videofinder number: | 1354 |
| Available to public: | no |
