AUTHENTICATING AND MEASURING QUALITY OF SERVICE OF MULTIMEDIA SIGNALS USING DIGITAL WATERMARK ANALYSES

摘要

A method of authenticating a media signal (100) and related software, systems and applications. The method transforms at least a portion of the media signal to a set of frequency coefficients in a frequency domain (104). For example, it applies a Fast Fourier Transform (FFT) or other frequency transform to blocks of a media signal, such as an image, audio or video signal. It adjusts a relationship between selected frequency coefficients to a reference value (128). This adjustment is selected so that an alteration to be detected such as a re-sampling operation or digital to analog-analog to digital conversion, alters the relationship. To detect the alteration, a detector computes the relationship in a potentially corrupted version of the signal (120). It then compares the result with a threshold value to detect whether the alteration has occurred. The degradation of a watermark signal is also used to measure quality of service of broadcast signals, such as audio and video.