Digital watermarking employing noise model

Abstract

A noise model is applied to digital signals, such as digital image and audio signals, to determine a tolerable noise level for embedding an auxiliary data carrying signal into the digital signals.

I claim:  
     
         1 . A method for determining a maximum imperceptible amount of noise which can be added to a digitized analog signal, the method comprising: 
 producing noise thresholds according to a psycho-sensory model;    determining a continuously differentiable function which approximates a quantization error permissible by the noise thresholds;    estimating a preferred gain for each one of the noise thresholds according to the continuously differentiable function, wherein the preferred gains for the respective noise thresholds collectively represent the maximum imperceptible amount of noise.    
     
     
         2 . The method of  claim 1  wherein the psycho-sensory model is a psycho-acoustic model.  
     
     
         3 . The method of  claim 1  wherein the psycho-sensory model is a psycho-visual model.  
     
     
         4 . The method of  claim 1  wherein determining the continuously differentiable function comprises: 
 determining a local quantization step-size function.  
 
     
     
         5 . A method for encoding embedded data in a digitized analog signal, the method comprising: 
 determining a maximum imperceptible amount of noise which can be added to a digitized analog signal by: 
 producing noise thresholds according to a psycho-sensory model;  
 determining a continuously differentiable function which approximates a quantization error permissible by the noise thresholds;  
 estimating a preferred gain for each one of the noise thresholds according to the continuously differentiable function, wherein the preferred gains for the respective noise thresholds collectively represent the maximum imperceptible amount of noise;  
 forming a basis signal from the digitized analog signal such that the basis signal is no greater than the maximum imperceptible amount of noise;  
 encoding the embedded data into the basis signal to form an encoded basis signal; and  
 adding the encoded basis signal to the digitized analog signal to form an encoded digitized analog signal.  
   
     
     
         6 . The method of  claim 5  wherein the psycho-sensory model is a psycho-acoustic model.  
     
     
         7 . The method of  claim 5  wherein the psycho-sensory model is a psycho-visual model.  
     
     
         8 . The method of  claim 5  wherein determining the continuously differentiable function comprises: 
 determining a local quantization step-size function.  
 
     
     
         9 . The method of  claim 5  wherein forming the basis signal comprises: 
 spread-spectrum chipping a noise threshold spectrum representing the noise thresholds in accordance with a stream of pseudo-random bits.  
 
     
     
         10 . A computer readable medium useful in association with a computer which includes a processor and a memory, the computer readable medium including computer instructions which are configured to cause the computer to determine a maximum imperceptible amount of noise which can be added to a digitized analog signal by: 
 producing noise thresholds according to a psycho-sensory model;    determining a continuously differentiable function which approximates a quantization error permissible by the noise thresholds;    estimating a preferred gain for each one of the noise thresholds according to the continuously differentiable function, wherein the preferred gains for the respective noise thresholds collectively represent the maximum imperceptible amount of noise.    
     
     
         11 . The computer readable medium of  claim 10  wherein the psycho-sensory model is a psycho-acoustic model.  
     
     
         12 . The computer readable medium of  claim 10  wherein the psycho-sensory model is a psycho-visual model.  
     
     
         13 . The computer readable medium of  claim 10  wherein determining the continuously differentiable function comprises: 
 determining a local quantization step-size function.  
 
     
     
         14 . A computer readable medium useful in association with a computer which includes a processor and a memory, the computer readable medium including computer instructions which are configured to cause the computer to encode embedded data in a digitized analog signal by: 
 determining a maximum imperceptible amount of noise which can be added to a digitized analog signal by: 
 producing noise thresholds according to a psycho-sensory model;  
 determining a continuously differentiable function which approximates a quantization error permissible by the noise thresholds;  
 estimating a preferred gain for each one of the noise thresholds according to the continuously differentiable function, wherein the preferred gains for the respective noise thresholds collectively represent the maximum imperceptible amount of noise;  
 forming a basis signal from the digitized analog signal such that the basis signal is no greater than the maximum imperceptible amount of noise;  
 encoding the embedded data into the basis signal to form an encoded basis signal; and  
 adding the encoded basis signal to the digitized analog signal to form an encoded digitized analog signal.  
   
     
     
         15 . The computer readable medium of  claim 14  wherein the psycho-sensory model is a psycho-acoustic model.  
     
     
         16 . The computer readable medium of  claim 14  wherein the psycho-sensory model is a psycho-visual model.  
     
     
         17 . The computer readable medium of  claim 14  wherein determining the continuously differentiable function comprises: 
 determining a local quantization step-size function.  
 
     
     
         18 . The computer readable medium of  claim 14  wherein forming the basis signal comprises: 
 spread-spectrum chipping a noise threshold spectrum representing the noise thresholds in accordance with a stream of pseudo-random bits.  
 
     
     
         19 . A computer system comprising: 
 a processor;    a memory operatively coupled to the processor; and    a noise threshold generator (i) which executes in the processor from the memory and (ii) which, when executed by the processor, causes the computer to determine a maximum imperceptible amount of noise which can be added to a digitized analog signal by: 
 producing noise thresholds according to a psycho-sensory model;  
 determining a continuously differentiable function which approximates a quantization error permissible by the noise thresholds;  
 estimating a preferred gain for each one of the noise thresholds according to the continuously differentiable function, wherein the preferred gains for the respective noise thresholds collectively represent the maximum imperceptible amount of noise.  
   
     
     
         20 . The computer system of  claim 19  wherein the psycho-sensory model is a psycho-acoustic model.  
     
     
         21 . The computer system of  claim 19  wherein the psycho-sensory model is a psycho-visual model.  
     
     
         22 . The computer system of  claim 19  wherein determining the continuously differentiable function comprises: 
 determining a local quantization step-size function.  
 
     
     
         23 . A computer system comprising: 
 a processor;    a memory operatively coupled to the processor; and    an encoder module (i) which executes in the processor from the memory and (ii) which, when executed by the processor, causes the computer to encode embedded data in a digitized analog signal by: 
 determining a maximum imperceptible amount of noise which can be added to a digitized analog signal by: 
 producing noise thresholds according to a psycho-sensory model;  
 determining a continuously differentiable function which approximates a quantization error permissible by the noise thresholds;  
 estimating a preferred gain for each one of the noise thresholds according to the continuously differentiable function, wherein the preferred gains for the respective noise thresholds collectively represent the maximum imperceptible amount of noise;  
 forming a basis signal from the digitized analog signal such that the basis signal is no greater than the maximum imperceptible amount of noise;  
 encoding the embedded data into the basis signal to form an encoded basis signal; and  
 adding the encoded basis signal to the digitized analog signal to form an encoded digitized analog signal.  
 
   
     
     
         24 . The computer system of  claim 23  wherein the psycho-sensory model is a psycho-acoustic model.  
     
     
         25 . The computer system of  claim 23  wherein the psycho-sensory model is a psycho-visual model.  
     
     
         26 . The computer system of  claim 23  wherein determining the continuously differentiable function comprises: 
 determining a local quantization step-size function.  
 
     
     
         27 . The computer system of  claim 23  wherein forming the basis signal comprises: 
 spread-spectrum chipping a noise threshold spectrum representing the noise thresholds in accordance with a stream of pseudo-random bits.