Spread spectrum watermark for embedded signalling

• US 5,848,155 A
• Filed: 09/04/1996
• Issued: 12/08/1998
• Est. Priority Date: 09/04/1996
• Status: Expired due to Term

• Current Assignee: NEC Corporation
• Original Assignee: NEC Research Institute, Inc. (NEC Corporation)
• Inventors: Cox, Ingemar J.
• Primary Examiner(s): CANGIALOSI, SALVATORE A
• Application Number:
  US08/708,331
• Time in Patent Office: 825 Days
• Field of Search: 380/4, 380/28, 380/34
• US Class Current: 382/191
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 2201/0052 Embedding of the watermark in the frequency domain
• CPC Class Codes: G06T 2201/0083 whereby only watermarked image required at decoder, e.g. source-based, blind, oblivious
• CPC Class Codes: H04N 1/32154 Transform domain methods H04N1/32309 takes precedence
• CPC Class Codes: H04N 1/3216 using Fourier transforms
• CPC Class Codes: H04N 1/32165 using cosine transforms
• CPC Class Codes: H04N 1/32197 according to the spatial domain characteristics of the transform domain components
• 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 2201/3233 of authentication information, e.g. digital signature, watermark
• CPC Class Codes: H04N 2201/327 which are undetectable to the naked eye, e.g. embedded codes
• CPC Class Codes: H04N 2201/328 Processing of the additional information

Abstract

A watermark is embedded into audio/video/image/multimedia data using spread spectrum methodology. The watermark is extracted from watermarked data without the use of an original or unwatermarked version of the data by using spatial or temporal local averaging of the frequency coefficients of the watermarked data.

Claims

1. A method of extracting a watermark from watermarked data comprising the steps of:

receiving watermarked data;

spectrum normalizing the watermarked data to generate a normalized signal;

correlating the normalized signal with predetermined PN sequences corresponding to predetermined symbols to provide correlated signals for each predetermined PN sequence;

deciding which PN sequence is present in the watermarked data based upon said correlated signals; and

extracting a watermark corresponding to a sequence of PN sequences present.

2. A method of extracting a watermark from watermarked data as set forth in claim 1, where said spectrum normalizing removes any spectral shaping performed when the watermark was inserted into the watermarked data.

3. A method of extracting a watermark from watermarked data as set forth in claim 1, where said spectrum normalizing determines local average of the frequency coefficients of the spectrum of the watermarked data and then divides each frequency coefficient of the spectrum of the watermarked data by the local average of the frequency coefficients.

4. A method of extracting a watermark from watermarked data as set forth in claim 1, where said watermarked data is audio data.

5. A method of extracting a watermark from watermarked data as set forth in claim 1, where said watermarked data is video data.

6. A method of extracting a watermark from watermarked data as set forth in claim 1, where said watermarked data is image data.

7. A method of extracting a watermark from watermarked data as set forth in claim 1, where said watermarked data is multimedia data.

8. A method for inserting a watermark into data comprising the steps of:

providing a watermark;

providing a spectrum of the data;

shaping the spectrum of the watermark commensurate with the average spectrum of the data; and

combining the shaped spectrum watermark with the spectrum of the data to obtain watermarked data spectrum.

9. A method for inserting a watermark into data as set forth in claim 8, where said average is a local average over a two dimensional region of said data.

10. A method for inserting a watermark into data as set forth in claim 9, where said average is a weighted average over a neighborhood of said data.

11. A method for inserting a watermark into data as set forth in claim 8, where said average is a temporal average over several frames of video data.

12. A method for inserting a watermark into data as set forth in claim 8, where said data is audio data.

13. A method for inserting a watermark into data as set forth in claim 8, where said data is video data.

14. A method for inserting a watermark into data as set forth in claim 8, where said data is image data.

15. A method for inserting a watermark into data as set forth in claim 8, where said data is multimedia data.

16. A method of inserting a watermark into data comprising the steps of:

providing a watermark signal,

providing a spectrum of the data;

shaping the spectrum of the watermark signal to be commensurate with the spectrum of the data; and

summing the shaped spectrum watermark signal with the spectrum of the data to obtain watermarked data spectrum.

17. A method of inserting a watermark into data as set forth in claim 16, where said shaping the spectrum of the watermark shapes the spectrum commensurate with temporal averages of frequency coefficients of the spectrum of the data.

18. A method of inserting a watermark into data as set forth in claim 16, where said shaping the spectrum of the watermark signal shapes the spectrum commensurate with local averages of frequency coefficients of the spectrum of the data.

19. A method of inserting a watermark into data as set forth in claim 16, where said data is audio data.

20. A method of inserting a watermark into data as set forth in claim 16, where said data is video data.

21. A method of inserting a watermark into data as set forth in claim 16, where said data is image data.

22. A method of inserting a watermark into data as set forth in claim 16, where said data is multimedia data.