Fast video multiplexing system
First Claim
1. A method of processing video signals comprising:
- (a) selecting one of a plurality of video input signals;
(b) applying the selected video input signal to an analog to digital video decoder;
(c) deriving from the selected video input signal an early synchronisation signal corresponding to the start of a field of the signal;
(d) applying the early synchronisation signal to a control input of the video decoder to enable an output of the video decoder;
(e) reading data from the enabled output corresponding to the first available field of the selected video input signal;
(f) repeating steps (a) to (e) for further selected video input signals; and
(g) combining the data read from the enabled output of the video decoder in each step (e) to form a time division multiplexed video signal.
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Abstract
The invention provides a method and apparatus for processing video data signals to generate a time division multiplexed video signal which incorporates a maxima number of fields from successive selected video input signals. The invention provides dual video decoder channels associated synchronisation circuits for generating an early synchronisation signal. The early synchronisation signals are applied to control inputs of the video decoders to enable reading of their output earlier than would normally be possible, avoiding delays in the combining of successive fields of video information in the video TDM signal. The provision of dual channels avoids delays due to lack of synchronisation between the different video sources.
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Citations
18 Claims
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1. A method of processing video signals comprising:
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(a) selecting one of a plurality of video input signals;
(b) applying the selected video input signal to an analog to digital video decoder;
(c) deriving from the selected video input signal an early synchronisation signal corresponding to the start of a field of the signal;
(d) applying the early synchronisation signal to a control input of the video decoder to enable an output of the video decoder;
(e) reading data from the enabled output corresponding to the first available field of the selected video input signal;
(f) repeating steps (a) to (e) for further selected video input signals; and
(g) combining the data read from the enabled output of the video decoder in each step (e) to form a time division multiplexed video signal. - View Dependent Claims (2, 3, 4)
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5. Apparatus for processing video signals comprising:
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switch means for selecting any one of a plurality of video input signals;
an analog to digital video decoder connected to an output of the switch means;
a synchronisation circuit associated with the video decoder for generating an early synchronisation signal from a selected video input signal corresponding to the start of a field of the signal and for applying the early synchronisation signal to a control input of the video decoder to enable an output thereof;
storage means connected to the output of the video decoder for storing data therefrom corresponding to the first available field of the selected video input signal; and
encoder means for combining data from the storage means corresponding to successive fields of selected video input signals into a time division multiplexer video signal. - View Dependent Claims (6, 7, 8, 9)
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10. A method of processing video signals comprising:
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(a) selecting one of a plurality of video input signals;
(b) applying the selected video input signal to an analog to digital video decoder;
(c) deriving from the selected video input signal a synchronisation signal corresponding to the start of a field of the signal;
(d) applying the synchronisation signal to a control input of the video decoder to enable an output of the video decoder;
(e) reading data from the enabled output corresponding to the first available field of the selected video input signal;
(f) repeating steps (a) to (e) for further selected video input signals; and
(g) combining the data read from the enabled output of the video decoder in each step (e) to form a time division multiplexed video signal. - View Dependent Claims (11, 12, 13)
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- 14. Apparatus for processing video signals comprising:
Specification