DPCM system with rate-of-fill control of buffer occupancy
First Claim
Patent Images
1. A method for communication by differential pulse code modulation, comprising the steps of:
- subtracting delayed predicted signals from input signals to produce difference signals;
adding said difference signals to said delayed predicted signals to produce current predicted signals;
at least delaying said current predicted signals to produce said delayed predicted signals;
coding said difference signals to form codewords of variable length having a variable data rate;
applying said codewords to a rate buffer at least part of the time for temporarily storing said codewords;
reading said codewords from said rate buffer;
generating a control signal representing the rate of fill of said rate buffer; and
controlling the rate of fill of said rate buffer by means including said control signal.
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Abstract
In a differential pulse code modulator for image-representative signals, a coder codes difference signals to produce coded signals which have a highly variable rate, which depends upon motion in the image being represented. A rate buffer receives the coded signals and generates a control signal representative, at least in part, of the rate of fill of the rate buffer. Various filters, decimators and/or coarse quantizers associated with the modulator have characteristics controlled by the control signal in order to tend to control the rate of fill of the rate buffer. This aids in preventing loss of information at the receiver.
128 Citations
22 Claims
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1. A method for communication by differential pulse code modulation, comprising the steps of:
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subtracting delayed predicted signals from input signals to produce difference signals; adding said difference signals to said delayed predicted signals to produce current predicted signals; at least delaying said current predicted signals to produce said delayed predicted signals; coding said difference signals to form codewords of variable length having a variable data rate; applying said codewords to a rate buffer at least part of the time for temporarily storing said codewords; reading said codewords from said rate buffer; generating a control signal representing the rate of fill of said rate buffer; and controlling the rate of fill of said rate buffer by means including said control signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. Apparatus for differential pulse code modulation of input signals representing data, comprising:
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subtracting means adapted for receiving said input signals for subtracting delayed predicted signals therefrom for producing difference signals; adding means coupled to said subtracting means for receiving said difference signals therefrom, and for adding said difference signals to said delayed predicted signals for producing current predicted signals; prediction means coupled to said adding means for receiving said current predicted signals therefrom for delaying said current predicted signals for producing said delayed predicted signals, and coupled to said subtracting means for coupling said delayed predicted signals thereto; coding means coupled to said subtracting means for receiving said difference signals therefrom for coding said difference signals for producing coded signals at a variable rate; rate buffer means coupled at least to said coding means and adapted for receiving at least said coded signals for temporarily storing signals to produce stored signals, and for producing said stored signals at an output terminal; rate control signal generating means coupled to said rate buffer means for generating a first control signal at least partially representative of the fill rate of said rate buffer means; and control means coupled to said rate control signal generating means for receiving said first control signal for, under the control of said first control signal, controlling the rate at which signals are applied to said rate buffer for controlling the rate of fill of said rate buffer means. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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Specification