Facsimile and static presentation processing – Static presentation processing – Attribute control
Patent
1984-08-01
1987-06-23
Masinick, Michael A.
Facsimile and static presentation processing
Static presentation processing
Attribute control
358148, 358150, H04N 713
Patent
active
046757228
DESCRIPTION:
BRIEF SUMMARY
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 62 .mu.s.
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 signals. 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.
We now propose that a plurality of predetermined digital sequences be used, each in a different line, from which both line and field syncs may be derived in a receiving apparatus.
Preferably, there will be just two predetermined sequences which will alternate line by line for the bulk of one field but one of the sequences will be repeated for a plurality of lines just prior to the end of one field while the other of the sequences will be repeated for a plurality of lines at the beginning of the next field. The sequences will then alternate as before.
The present invention provides apparatus for deriving synchronisation signals from a received television signal which has a sequence of a plurality of different digital words; each is a respective one of a plurality of lines as synchronisation signals, comprising means for generating a first signal indicative of detection of one of the digital words, means for generating a further signal indicative of detection of a further digital word, means for evaluating the first and further signals to determine the sequence and timing of the first and further signals whereby to generate a signal indicative of synchronisation signal acquisition for initiating generating of receiver sync signals at line frequency.
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 multiple timing of each line in the frame.
FIG. 3 shows a block diagram of a receiver incorporating the present invention;
FIG. 4 shows a state diagram to explain the operation of the circuit shown in FIG. 3.
FIG. 5 shows a block diagram of a further receiver incorporating the present invention; and
FIGS. 6A and 6B show state diagrams to explain the operation of the circuit shown in FIG. 5.
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 satellite FM transmission channel, since the spectral width of the FM signal is a f
REFERENCES:
patent: 4353130 (1982-10-01), Carasso
patent: 4483011 (1984-11-01), Brown
"Multiple Sound Channels in Satellite Broadcasting", Windram, IEE Proc, Section AAI, vol. 129, No. 7, Part A, Sep. 1982, pp. 528-531.
"Extended-Definition Television Service", Robson, IEE Proceedings Section AAI, vol. 129, No. 7, Part A, Sep. 1982, pp. 485-492.
Independent Broadcasting Authority
Masinick Michael A.
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