Detecting a watermark embedded in an information signal

• US 5,933,798 A
• Filed: 07/16/1997
• Issued: 08/03/1999
• Est. Priority Date: 07/16/1996
• Status: Expired due to Term

• Current Assignee: Civolution BV (Kudelski SA)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Linnartz, Johan P. M. G.
• Primary Examiner(s): SHAH, KAMINI S
• Application Number:
  US08/895,250
• Time in Patent Office: 748 Days
• Field of Search: 364/572, 364/471.01, 380/4, 380/25, 707/515, 707/715, 702/191
• US Class Current: 702/191
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 2201/0065 Extraction of an embedded watermark; Reliable detection
• CPC Class Codes: H04N 2005/91335 the copy protection signal being a watermark
• CPC Class Codes: H04N 21/23892 involving embedding information at multiplex stream level, e.g. embedding a watermark at packet level
• CPC Class Codes: H04N 21/8358 involving watermark protecting executable software by watermarking G06F21/16; image watermarking in general G06T1/0021; watermarks inserted in still images for transmission purposes H04N1/32144; inserting watermarks during video coding H04N19/467
• CPC Class Codes: H04N 5/913 for scrambling ; for copy protection
• CPC Class Codes: H04N 7/08 Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band , e.g. by time division H04N7/007 takes precedence
• CPC Class Codes: H04N 7/52 Systems for transmission of a pulse code modulated video signal with one or more other pulse code modulated signals, e.g. an audio signal or a synchronizing signal assembling of a multiplex stream by combining a video stream with other content or additional data, remultiplexing of multiplex streams, insertion of stuffing bits into the multiplex stream, assembling of a packetised elementary stream at server side H04N21/236; disassembling of a multiplex stream, remultiplexing of multiplex streams, extraction or processing of Service Information, disassembling of packetised elementary stream at client side H04N21/434

Abstract

To detect a watermark signal embedded within an information signal, predictive filtering is applied to either the information signal, a plurality of applied watermark signals, or both types of signals. After the filtering, a correlation is determined between the information signal and the watermark signals. The amount of the correlation is indicative of whether a particular watermark is embedded within the information signal.

Claims

1. A method of detecting a watermark signal embedded in an information signal, comprising the steps of:

providing an applied watermark signal;

predictive filtering of the information signal or the applied watermark signal or both;

correlating the information signal and the applied watermark signal; and

evaluating the result of said correlation.

2. The method of claim 1, wherein the predictive filtering is adapted to predetermined statistical properties of the information signal.

3. The method of claim 1, wherein both the information signal and applied watermark signal are predictive filtered and the predictive filter steps are the same.

4. A method of detecting a watermark embedded in an information signal, comprising the steps of:

filtering the information signal using filter coefficients determined by an applied watermark signal, and by a model of the statistical properties of the information signal;

and evaluating the result of said filtering.

5. An arrangement for detecting a watermark signal embedded in an information signal, comprising:

correlation means for correlating the information signal and an applied watermark signal and;

evaluation means for evaluating the result of said correlation, communicating with the correlation means; and

a predictive filter for filtering the information signal or for filtering the applied watermark, or both, and connected for applying the filtered signal and the filtered watermark to the correlation means.

6. The arrangement of claim 5, wherein the predictive filter includes means to filter depending on predetermined statistical properties of the information signal.

7. The arrangement of claim 5, wherein the predictive filter includes a first predictive filter for filtering the information signal and a second predictive filter for filtering the applied water mark and both predictive filters are identical.

8. An arrangement for detecting a watermark signal embedded in an information signal, comprising:

a filter for filtering said information signal using filter coefficients;

calculation means for calculating said filter coefficients in dependence on an applied watermark and a model of the statistical properties of the information signal; and

means for evaluating the result of said filtering.