Facsimile and static presentation processing – Static presentation processing – Attribute control
Patent
1984-03-23
1987-01-27
Shepperd, John W.
Facsimile and static presentation processing
Static presentation processing
Attribute control
358 12, 358148, 358150, H04N 504
Patent
active
046397647
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the transmission and/or reception of television pictures.
In our co-pending International Patent Application No. PCT/GB83/00022 (Publication No. WO 83/02704) there are disclosed a method and system for transmitting and/or receiving colour television signals which we have called MAC (Multiplexed Analogue Component). In this system, the chrominance and luminance components of the picture are separated and transmitted in time compressed form. Information must be encoded on the compressed signal to provide timing data for horizontal and vertical synchronisation of the received picture.
Unlike convention television coding systems (e.g. PAL) MAC does not have an exclusive voltage level for synchronisation transmission. The chrominance waveform uses the full voltage range of the signal. Thus different methods of synchronisation coding are required.
Horizontal synchronisation information (`linesync`) is decoded by detection of the fixed position voltage changes (transitions) at the start and end of the time-compressed luminance information. These transitions remain constant and using `flywheel` methods can reliably be detected in the presence of other similarly-spaced transitions in the picture information.
However, there is no equally-apparent way to encode vertical or field synchronisation information.
The present invention involves the provision of a vertical synchronisation signal which can be used with separated component signal transmission systems such as the MAC system.
The present invention provides a transmission system for transmitting television signals of the type including separate chrominance and luminance components within individual line periods, the system comprising means for separating the chrominance and luminance components from a picture signal to provide line scan periods having said separated components, characterised in that there are provided means for inserting a vertical synchronisation signal within each field of television signals, said vertical synchronisation signal having a duration of one line period and an amplitude component greater than that of a corresponding component of the separated picture signal.
The present invention also provides a receiving system for receiving signals having a vertical synchronisation signal as abovedescribed.
In order that the present invention may be more readily understood, an embodiment thereof will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 shows the basic form of a MAC signal;
FIG. 2 shows a diagram for use in explaining the present invention;
FIG. 3 shows two waveforms provided by apparatus according to the present invention;
FIG. 4 shows a block diagram of part of transmitting apparatus wherein the synchronisation waveforms of FIG. 3 are inserted in the signal for transmission; and
FIG. 5 shows a block diagram of part of receiving apparatus arranged to detect the synchronisation waveforms of FIG. 3.
Referring to FIG. 1, there is shown a representation of a basic MAC signal of one line length (64 .mu.sec) from which it will be seen that the chrominance waveform uses the full voltage range or available signal amplitude S.sub.A of the signal. There is no exclusive voltage level for synchronisation, as previously stated, and therefore other methods must be utilised. Transitions 1 and 2 occurring at the beginning and end of the luminance component can readily be detected to provide horizontal synchronisation information. Further details of the basic MAC signal and its transmission and reception can be obtained from the aforementioned International (PCT) Application.
Due to the nature of the MAC signal, transmission of luminance (Y) and colour difference (U,V) signals is achieved without any interaction between these signals. In addition, there is no restriction on the relative amplitudes for the Y and U or V signals provided they remain within their allotted envelopes. Therefore the limits of the colour signal that may be transmitted by the MAC system can be r
REFERENCES:
patent: 4245235 (1981-01-01), Poetsch
patent: 4335393 (1982-06-01), Pearson
The Radio and Electronic Engineer, vol. 52, No. 7, Jul. 1982 (London, GB), "F.W.S. Television System for DBS", pp. 311-313.
T. S. Robson, "Extended-Definition Television Service", IEE Proc., vol. 129, Pt. A, No. 7, Sep. 1982, pp. 485-492.
K. Lucas and M. D. Windram, "Direct-Television Broadcasts by Satellite--Desirability of a New Transmission Standard", IBA Report 116/81, pp. 1-19.
Independent Broadcasting Authority
Shepperd John W.
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