Method and apparatus for conveying information signals
First Claim
1. A method of conveying television signals from a source to a receiver by way of a medium, comprising the steps of segregating signals from the source into component signals in a corresponding plurality of channels corresponding to progressively less visually significant information, forming a composite signal, for conveyance by the said medium, by subjecting the component signals from the said channels to a combining operation to form a composite signal with the powers of the component signals in the composite signal varying directly in dependence on the visual significance of the information in the channels, the combining operation being such as to be reversible to recover the component signals from the composite signal, and, at the receiver, recovering a number of the component signals from the composite signal conveyed to the receiver by the said medium and forming a television signal from the recovered signals.
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Abstract
Video signals from a source are digitized and applied to a source coder which segregates the signals into four channels (CH1 to CH4) of progressively less visual significance. CH1 carries basic picture information at a relatively low resolution. CH2 to CH4 carry differential information at progressively higher resolutions. The four channels signals are applied to respective coders and the digital outputs are combined in a matrix with voltage levels falling off as visual significance decreases. Received signals, transmitted say by way of a satellite, are applied to a first, high level decoder which extracts the digital waveform for CH1 as DCH1. This is recoded and subtracted from the input to provide a signal to a decoder which recovers CH2 as DCH2, and so on. DCH1 to DCH4 are applied to a source decoder complementary to the coder to recover the source signal. Low significant channels can be omitted at the transmitter, or not be recovered at the receiver to adapt to the prevailing signal to noise performance.
78 Citations
19 Claims
- 1. A method of conveying television signals from a source to a receiver by way of a medium, comprising the steps of segregating signals from the source into component signals in a corresponding plurality of channels corresponding to progressively less visually significant information, forming a composite signal, for conveyance by the said medium, by subjecting the component signals from the said channels to a combining operation to form a composite signal with the powers of the component signals in the composite signal varying directly in dependence on the visual significance of the information in the channels, the combining operation being such as to be reversible to recover the component signals from the composite signal, and, at the receiver, recovering a number of the component signals from the composite signal conveyed to the receiver by the said medium and forming a television signal from the recovered signals.
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12. A method of conveying television signals from a source to a receiver by way of a medium, comprising the steps of segregating signals from the source into component signals in a corresponding plurality of channels corresponding to progressively less visually significant information, forming a composite signal, for conveyance by the said medium, by subjecting the component signals from the said channels to a combining operation to form a composite signal with the powers of the component signals in the composite signal varying directly in dependence on the significance of the information in the channels, the combining operation being such as to be reversible to recover the component signals from the composite signal, and, at the receiver, recovering a number of the component signals from the composite signal conveyed to the receiver by the said medium and reconstituting an information signal from the recovered signals.
- 13. Apparatus for transmitting information signals from a source thereof, comprising first coding means which segregate the information signals into a plurality of channels which carry progressively less significant information, second coding means which code the signals in the channels into respective coded signals with power levels varying directly with said information significance, and combining means which combine the coded signals into a composite signal in accordance with a combining operation such as to be reversible to recover the component signals from the composite signal.
- 16. Apparatus for recovering an information signal from a received composite signal including components with different power levels corresponding to different levels of information comprising a series of decoding means operative to detect and decode successively lower levels of information in the received composite signal in accordance with the power levels thereof, and further decoding means operative to decode the signals from the series of decoding means into the information signal.
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19. A method of recovering information from a signal containing coded information at different amplitude levels, comprising the steps of decoding the signal at a succession of decreasing signal amplitude levels n=1, 2 and so on such that, at each level n the coded information for subsequent levels n+1 and so on does not influence the decoding, and re-coding the resultant decoded signal at each level and subtracting the re-coded signal from the signal which was decoded at the level n to form the signal which is decoded at level n+1.
Specification