Methods and apparatus to detect a blank frame in a digital video broadcast signal
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. An apparatus to detect a blank image within a compressed media signal, the apparatus comprising:
a buffer to store a compressed digital image, the compressed digital image being a frame of the compressed media signal;
a blank frame candidate identifier means to:
analyze a total number of bits in the compressed digital image stored in the buffer to determine if the compressed digital image has a data size less than a first threshold;
when the data size is less than the first threshold, determine a number of bits in multiple areas of the compressed digital image and store the number of bits associated with each of the multiple areas in the buffer;
analyze the number of bits in multiple areas of the compressed digital image stored in the buffer to determine if a deviation between the number of bits within the multiple areas is less than a second threshold;
when in response to the deviation between the number of bits within the multiple areas being less than the second threshold, identify the compressed digital image as a blank image candidate; and
when the compressed digital image is not identified as a blank image candidate, discard the compressed digital image from the buffer;
a blank frame tester means to:
when the compressed digital image is identified as a blank image candidate, determine a number of DC values of the blank image candidate that meet a criterion and store the DC values in the buffer;
compare the determined number of DC values stored in the buffer meeting the criterion to a third threshold; and
identify the compressed digital image as a blank image if the determined number of DC values exceeds the third threshold; and
a commercial identifier means to:
in response to identifying the blank image, identify an advertisement of a media stream associated with the compressed digital image; and
transmit the advertisement to a data processing center;
wherein the blank frame tester means determines the number of DC values meeting the criterion by determining a number of relative DC values that are less than a DC value threshold.