Monitoring detectability of a watermark message

摘要

A system for monitoring detectability of a watermark message produced by a watermarking encoder includes an input that receives a watermarked signal having spectral channels in which the watermark message is embedded. The system also includes channel separators each associated with a respective spectral channel of the watermarked signal and configured to separate the watermarked signal into spectral channels. The system also includes bin separators configured to separate the spectral channels into frequency bins. The system also includes a detector configured to detect a frequency bin corresponding to a symbol that appears in a plurality of the spectral channels. The system also includes a detectability estimator configured to establish a measure of the detectability of the watermark message embedded in the watermarked signal based at least in part on the frequency bin corresponding to the symbol that appears in the plurality of the spectral channels.

主权项

1. A method of monitoring detectability of a watermark message produced by a watermarking encoder, the method comprising:
receiving a watermarked signal in which the watermark message is embedded; separating the watermarked signal into spectral channels by:
spectrally shifting the watermarked signal such that a center frequency of the spectral channel shifts to 0 Hz, andlow pass filtering the spectrally shifted watermarked signal to obtain the spectral channel; separating the spectral channels into frequency bins; for each of the spectral channels, identifying a frequency bin corresponding to the synchronization symbol of the watermark message; establishing a timing of the synchronization symbol based on an aggregate of the frequency bins corresponding to the synchronization symbol identified for the spectral channels to obtain a message clock; adding delays to the message clock to establish timing for symbols in the watermark message other than the synchronization symbol; for each of the symbols in the watermark message other than the synchronization symbol, at a timing corresponding to the timing for each symbol, for each of the spectral channels:
identifying a frequency bin with highest amplitude,comparing an amplitude of the frequency bin with the highest amplitude to a threshold,providing a bin number of the frequency bin with the highest amplitude based on the comparison of the amplitude of the frequency bin with the highest amplitude and the threshold, andstoring the bin number of the frequency bin with the highest amplitude to a respective hold register of a plurality of hold registers; combining the bin numbers stored in the hold registers to obtain a decoded message for each spectral channel; for each of the spectral channels, comparing the decoded message to a reference message to obtain a symbol number of the watermark message for each correct symbol in the decoded message; attempting to assemble a complete watermark message in a predetermined period of time by combining symbol numbers of the watermark message from the spectral channels; and establishing the detectability measure of the watermark message embedded in the watermarked signal based on whether the complete watermark message is assembled in the predetermined period of time.