Analytics-modulated coding of surveillance video

Abstract

A method and apparatus for encoding surveillance video where one or more regions of interest are identified and the encoding parameter values associated with those regions are specified in accordance with intermediate outputs of a video analytics process. Such an analytics-modulated video compression approach allows the coding process to adapt dynamically based on the content of the surveillance images. In this manner, the fidelity of the region of interest is increased relative to that of a background region such that the coding efficiency is improved, including instances when no target objects appear in the scene. Better compression results can be achieved by assigning different coding priority levels to different types of detected objects.

What is claimed is: 
     
         1 . A method, comprising:
 assigning a class from a plurality of classes to a foreground object from a video frame having a plurality of pixels, each class from among the plurality of classes having associated therewith a quantization parameter value;   producing a plurality of discrete cosine transform (DCT) coefficients for pixels from the plurality of pixels of the video frame associated with the foreground object;   quantizing the plurality of DCT coefficients associated with the foreground object based on the quantization parameter value associated with the class assigned to the foreground object; and   coding the quantized DCT coefficients associated with the foreground object.   
     
     
         2 . The method of  claim 1 , wherein the foreground object is a first foreground object, the class assigned to the foreground object being a first class, the quantization parameter value associated with the first class being a first quantization parameter value, the method further comprising:
 assigning a second class from among the plurality of classes to a second foreground object from the video frame, the second class being different from the first class;   producing a plurality of DCT coefficients for pixels from the plurality of pixels of the video frame associated with the second foreground object;   quantizing the plurality of DCT coefficients associated with the second foreground object based on the quantization parameter value associated with the second class assigned to the second foreground object; and   coding the quantized DCT coefficients associated with the second foreground object.   
     
     
         3 . The method of  claim 1 , wherein the video frame includes a background portion, the method further comprising:
 producing a plurality of DCT coefficients for pixels from the plurality of pixels of the video frame associated with the background portion of the video frame;   quantizing the plurality of DCT coefficients associated with the background portion of the video frame based on a quantization parameter value greater than the quantization parameter associated with each class from among the plurality of classes; and   coding the quantized DCT coefficients associated with the background portion of the video frame.   
     
     
         4 . The method of  claim 1 , wherein:
 the class assigned to the foreground object is a first class, the plurality of classes including a second class different from the first class,   the first class having an associated coding priority and an associated quantization parameter value,   the second class having an associated coding priority and an associated quantization parameter value,   the quantization parameter value associated with the first class being less than the quantization parameter value associated with the second class when the coding priority associated with the first class is greater than the coding priority associated with the second class.   
     
     
         5 . The method of  claim 1 , wherein the plurality of pixels of the video frame are organized into a plurality of blocks of pixels, the method further comprising:
 producing a plurality of DCT coefficients for each block of pixels from the plurality of blocks of pixels of the video frame associated with the foreground object;   quantizing the plurality of DCT coefficients of each block of pixels associated with the foreground object based on the quantization parameter value associated with the class assigned to the foreground object; and   coding the quantized DCT coefficients associated with the foreground object.   
     
     
         6 . The method of  claim 1 , wherein:
 the foreground object includes at least one block of pixels from a plurality of blocks of pixels of the video frame, the at least one block of pixels associated with the foreground object defining a contour associated with the foreground object.   
     
     
         7 . A method, comprising:
 assigning a class from among a plurality of classes to a foreground object from a video frame having a plurality of pixels;   adjusting a quantization parameter value associated with the foreground object based on at least one of a target bit rate and a weight associated with the class assigned to the foreground object, the weight being based on a coding priority associated with the class assigned to the foreground object;   producing a plurality of DCT coefficients for pixels from the plurality of pixels of the video frame associated with the foreground object;   quantizing the DCT coefficients associated with the foreground object based on the adjusted quantization parameter value; and   coding the quantized DCT coefficients associated with the foreground object.   
     
     
         8 . The method of  claim 7 , further comprising:
 coding the video frame via a first-pass of a low-complexity coding operation;   adjusting a human visual system factor associated with the video frame based on the coded video frame; and   adjusting the quantization parameter value associated with the foreground object based on at least one of the target bit rate, the weight associated with the class assigned to the foreground object, and the adjusted human visual system factor.   
     
     
         9 . The method of  claim 7 , wherein the foreground object is a first foreground object, the class assigned to the foreground object being a first class, the weight associated with the first class being a first weight, the quantization parameter value associated with the first foreground object being a first quantization parameter value, the method further comprising:
 assigning a second class from among the plurality of classes to a second foreground object from the video frame, the second class being different from the first class;   adjusting a second quantization parameter value associated with the second foreground object based on at least one of a target bit rate and a second weight associated with the second class assigned to the second foreground object, the second quantization parameter value being different from the first quantization parameter value, the second weight being different from the first weight;   producing a plurality of DCT coefficients for pixels from the plurality of pixels of the video frame associated with the second foreground object;   quantizing the DCT coefficients associated with the second foreground object based on the adjusted second quantization parameter value; and   coding the quantized DCT coefficients associated with the second foreground object.