Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1984-08-10
1988-02-09
Groody, James J.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358 11, 358 12, H04N 708
Patent
active
047244860
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for transmitting and/or receiving television video signals in component form, which components have been time compressed and placed sequentially so as to occupy, together with the necessary sync and clamping signals, a period substantially identical to the existing line period e.g. approximately 64 .mu.S.
2. Prior Art
It has already been proposed to compress the video component signals to such an extent that an audio signal can be included either before or after the video component signal, within the line period. It is preferred that this audio signal takes the form of a digital signal placed before the video components signal. Further, it has been proposed to add to this digital signal a predetermined sequence of digits for use as either a sound or line sync signal.
SUMMARY OF THE INVENTION
We propose that one or more of said predetermined digital sequences can be replaced, preferably by a further digital sequence, in order to signal additional information to a receiver.
The present invention provides receiving apparatus for receiving multiplexed analogue component signals each of which represents a line of a television picture and includes a burst of digital signals, at least one of the multiplexed analogue component signals including at a predetermined location within its digital burst an indication of further information, the apparatus comprising a demodulating device for demodulating received multiplexed analogue component signals, means responsive to the output of the demodulating device for synchronising the receiving apparatus to the received multiplexed analogue component signals, and a data extraction circuit responsive to the synchronising means for extracting from the demodulated signals the indication of further information and for controlling the operation of the demodulating device in accordance with the further information.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the present invention be more readily understood, reference will now be made to the accompanying drawings, in which:
FIG. 1 shows diagrammatically a multiplexed component signal showing the time division multiplex between the component parts thereof;
FIG. 2 shows diagrammatically a frame of C-MAC signals offset by 1/2 frame and 1/2 line as well as the multiplex timing of each line in the frame.
FIG. 3 shows a block diagram of a receiver incorporating the present invention;
FIG. 4 shows a more detailed block diagram of a part of the receiver shown in FIG. 3;
FIG. 5 shows a state diagram to explain the operation of the circuit shown in FIG. 4;
FIG. 6 shows a more detailed block diagram of modification to the block diagram shown in FIG. 4; and
FIGS. 7A and 7B show state diagrams to explain the operation of the circuit shown in FIG. 6.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
The Multiplex Analogue Components (MAC) system for whom television signal transmission replaces the colour subcarrier coding of NTSC, PAL and SECAM with a single method of time compression. The conventional studio colour coder is replaced by a MAC coder which separately time compresses each active picture line (52 .mu.s nominally) of luminance (Y) and chrominance (alternate lines contain U and V). By using either charge-coupled devices (ie CCDs) or digital storage, these compressed luminance and chrominance components can be placed in sequence within the 64 .mu.s of each line period. Conventional sync pulses, designed for receiver technology of 30 years ago, are no longer required and are replaced by other synchronisation information within the waveform. The colour subcarrier burst is no longer required, and any timing information required for future developments such as extended definition receivers can be derived from the video and sound/data signals.
This time compression results in a proportionate increase in the bandwidth required to pass the signal. The extra bandwidth of the time-compressed baseband signal can be accommodated within a sate
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M. D. Windram, "Multiple Sound Channels in Satellite Broadcasting", IEE Proceedings, Section AAI, vol. 129, No. 7, part A, pp. 528-531, 9/82.
T. S. Robson, "Extended-Definition Television Service", IEE Proceedings, section AAI, vol. 129, No. 7, Part A, pp. 485-492, 9/82.
Harding Wilfrid B.
Tonge Gary J.
Groody James J.
Harvey David E.
Independent Broadcasting Authority
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