Methods and apparatus to detect a blank frame in a digital video broadcast signal

Abstract

Methods and apparatus to detect blank images in a digital video broadcast signal are disclosed. An example method of detecting a blank image includes receiving a compressed digital image including a plurality of DC values, analyzing a total number of bits in the digital image to determine if the digital image has a data size small enough to be a blank frame candidate, if the data size is small enough for the digital image to be a blank frame candidate, analyzing multiple areas of the digital image to determine if the multiple areas exhibit substantially a same complexity, if the multiple areas exhibit substantially the same complexity, determining a number of DC values in the plurality of DC values that meet a criterion, comparing the determined number of DC values meeting the criterion to a threshold, and identifying the received digital image as a blank image if the determined number of DC values exceeds the threshold.

1 . A method of detecting a blank image comprising:
 receiving a compressed digital image including a plurality of DC values;   analyzing a total number of bits in the digital image to determine if the digital image has a data size small enough to be a blank frame candidate;   if the data size is small enough for the digital image to be a blank frame candidate, analyzing multiple areas of the digital image to determine if the multiple areas exhibit substantially a same complexity;   if the multiple areas exhibit substantially the same complexity, determining a number of DC values in the plurality of DC values that meet a criterion;   comparing the determined number of DC values meeting the criterion to a threshold; and   identifying the received digital image as a blank image if the determined number of DC values exceeds the threshold.   
     
     
         2 . A method as defined in  claim 1  wherein determining the number of DC values meeting the criterion comprises, for each DC value except for the first DC value in the plurality, determining if a difference between the DC value and a previous DC value is substantially zero. 
     
     
         3 . A method as defined in  claim 1  wherein the plurality of DC values are contained within a same slice of a frame. 
     
     
         4 . A method as defined in  claim 1  wherein determining the number of DC values meeting the criterion is performed without decompressing the compressed digital image. 
     
     
         5 . A method as defined in  claim 1  wherein determining the number of DC values meeting the criterion comprises determining a number of relative DC values in the plurality of DC values that are substantially equal to zero. 
     
     
         6 . A method as defined in  claim 1  wherein determining the number of DC values meeting the criterion comprises determining a number of relative DC values in the plurality of DC values that are less than a threshold. 
     
     
         7 . A method of detecting a blank image comprising:
 analyzing a total number of bits in a compressed digital image to determine if the digital image has a data size small enough to be a blank frame candidate;   if the data size is small enough for the digital image to be a blank frame candidate, analyzing multiple areas of the digital image to determine if the multiple areas exhibit substantially a same complexity;   if the multiple areas exhibit substantially the same complexity, parsing at least a portion of the compressed digital image into a plurality of blocks;   counting a number of blocks in the plurality of blocks that have substantially identical brightness values; and   comparing the number of blocks counted to a threshold to determine if the digital image is a blank image.   
     
     
         8 . A method as defined in  claim 7  wherein parsing the at least the portion of the compressed digital image comprises parsing a slice of the compressed digital image. 
     
     
         9 . A method of detecting a blank image comprising:
 analyzing a total number of bits in a frame to determine if the digital image has a data size small enough to be a blank frame candidate;   if the data size is small enough for the frame to be a blank frame candidate, analyzing multiple areas of the frame to determine if the multiple areas exhibit substantially a same complexity;   if the multiple areas exhibit substantially the same complexity, analyzing DC values of luminance blocks associated with the frame to determine a number of the luminance blocks having substantially the same DC value; and   identifying the frame as a blank image if the number exceeds a threshold.   
     
     
         10 . A method as defined in  claim 9  wherein analyzing the DC values of the luminance blocks comprises counting a number of relative DC values that are substantially zero. 
     
     
         11 . A method as defined in  claim 9  wherein analyzing the DC values of the luminance blocks comprises generating a histogram representative of the DC values. 
     
     
         12 . A method as defined in  claim 9  wherein analyzing the DC values of the luminance blocks comprises comparing DC values of sequential pairs of DC values to determine if a DC value difference exceeds a difference threshold. 
     
     
         13 . A method as defined in  claim 9  wherein analyzing the DC values of the luminance blocks associated with the frame comprises analyzing the DC values of the luminance blocks associated with a slice of the frame. 
     
     
         14 . An apparatus for detecting a blank image comprising:
 a blank frame candidate identifier to identify a compressed digital image as a blank frame candidate if the digital image has a data size less than a first threshold and if multiple areas of the digital image exhibit substantially a same complexity;   a parser to parse at least a portion of the compressed digital image into a plurality of blocks;   a counter to count a number of blocks in the plurality of blocks that have a substantially identical brightness; and   a comparator to compare the number of blocks counted by the counter to a threshold to determine if the digital image is a blank image.   
     
     
         15 . An apparatus as defined in  claim 14  wherein the comparator identifies the digital image as a blank image if the determined number of blocks exceeds the threshold. 
     
     
         16 . An apparatus as defined in  claim 14  wherein the compressed digital image is an MPEG encoded image and the average brightness value is an MPEG DC value. 
     
     
         17 . An apparatus as defined in  claim 14  wherein the counter counts the number of blocks in the plurality of blocks that have the substantially identical brightness without decompressing the compressed digital image. 
     
     
         18 . An apparatus as defined in  claim 14  wherein the blocks comprise luminance blocks each of which includes a DC value indicative of a brightness value of the luminance block, and further comprising a DC value comparator to compare the DC values of sequential pairs luminance blocks to determine if the sequential pairs have substantially the same brightness. 
     
     
         19 . An apparatus as defined in  claim 18  wherein the counter cooperates with the DC value comparator to count the number of blocks in the plurality of blocks. 
     
     
         20 . An apparatus for detecting a blank image comprising:
 a blank frame candidate identifier to identify a compressed digital image as a blank frame candidate if the digital image has a data size less than a first threshold and if multiple areas of the digital image exhibit substantially a same complexity;   a parser to parse at least a portion of the compressed digital image into a plurality of blocks;   a histogram generator to create a histogram representative of brightness values associated with the plurality of blocks; and   a comparator to compare at least a portion of the histogram to a threshold to determine if the digital image is a blank image.   
     
     
         21 . An apparatus as defined in  claim 20  wherein the comparator identifies the digital image as a blank image if the histogram indicates that more than the threshold of blocks have substantially the same brightness. 
     
     
         22 . An apparatus as defined in  claim 20  wherein the compressed digital image is an MPEG encoded image and the brightness values are MPEG DC values. 
     
     
         23 . An apparatus as defined in  claim 20  wherein the histogram generator creates the histogram without decompressing the compressed digital image. 
     
     
         24 . An apparatus as defined in  claim 20  wherein the blocks comprise luminance blocks each of which includes a DC value indicative of a brightness value of the luminance block. 
     
     
         25 . A method of detecting a blank image comprising:
 determining a number of bits contained in each area of a frame without extracting DC values from the frame;   determining a number of areas of the frame having substantially the same number of bits without extracting the DC values from the frame; and   identifying the frame as a blank image without extracting the DC values from the frame if the determined number of areas exceeds a threshold.   
     
     
         26 . A method as defined in  claim 25  wherein determining the number of bits, determining the number of areas and identifying the frame as a blank image are performed without decompressing the frame. 
     
     
         27 . A method as defined in  claim 25  wherein identifying the frame as a blank image if the determined number of areas exceeds a threshold further comprises:
 analyzing DC values of luminance blocks associated with a slice of the frame to determine a number of the luminance blocks having substantially the same DC value; and 
 identifying the frame as a blank image only if the number exceeds a threshold. 
 
     
     
         28 . An apparatus to detect a blank image comprising:
 an area byte calculator to determine a number of bytes contained in an area of a frame without extracting DC values from the frame;   an area count comparator to compare a characteristic of the areas of the frame determined by the area byte calculator to a threshold to determine if the frame is a blank image without extracting the DC values from the frame.   
     
     
         29 . An apparatus as defined in  claim 28  wherein the area byte calculator counts the number of bytes in a slice without decompressing the frame. 
     
     
         30 - 45 . (canceled) 
     
     
         46 . A method to detect blank frames in a compressed digital signal comprising:
 identifying a blank candidate by analyzing at least one bit allocation associated with a frame without extracting DC values from the frame; and   determining if the blank frame candidate is a blank frame by analyzing the DC values in at least one area of the blank candidate.   
     
     
         47 - 60 . (canceled)