Patent ID: 7317811

Claim:
A method of detecting a watermark among a plurality of reproduced compressed frames of data including a temporal watermark sequence, the reproduced frames of data having been derived from respective original frames of data, the method comprising: creating an output transform frame of zero values, decoding the non-zero quantized transform coefficients for each compressed frame, scaling the quantized transform coefficients by the corresponding value in the temporal watermark sequence, adding each quantized transform coefficient found to its corresponding location in the transform frame to form an accumulated transform frame, computing the inverse transform on the accumulated transform frame to obtain an aggregate frame of data points; selecting peak data points of the aggregate frame of data points; computing correction information from deviations between the positions of the peak data points within the aggregate frame and expected positions of those peak data points; modifying positions of at least some of the data of at least some of the reproduced frames of data using the correction information such that those reproduced frames of data more closely coincide with respective ones of the original frames of data; and detecting the watermark from among the modified reproduced frames of data.