Digital watermark embedding method and apparatus, and digital watermark

• US 20030091213A1
• Filed: 12/24/2002
• Published: 05/15/2003
• Est. Priority Date: 04/24/2001
• Status: Active Grant

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Koto, Shinichiro, Yamakage, Tomoo, Yamada, Hisashi, Kambayashi, Toru, Muratani, Hirofumi
• Granted Patent: US 6,741,723 B2
• Time in Patent Office: Days
• US Class Current: 382/100
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 1/0064 Geometric transfor invariant watermarking, e.g. affine transform invariant
• CPC Class Codes: G06T 2201/0052 Embedding of the watermark in the frequency domain
• CPC Class Codes: G06T 2201/0065 Extraction of an embedded watermark; Reliable detection
• CPC Class Codes: G06T 2201/0083 whereby only watermarked image required at decoder, e.g. source-based, blind, oblivious
• CPC Class Codes: H04N 1/32149 Methods relating to embedding, encoding, decoding, detection or retrieval operations
• CPC Class Codes: H04N 1/32154 Transform domain methods H04N1/32309 takes precedence
• CPC Class Codes: H04N 1/32165 using cosine transforms
• CPC Class Codes: H04N 1/32187 with selective or adaptive application of the additional information, e.g. in selected frequency coefficients
• CPC Class Codes: H04N 1/32203 Spatial or amplitude domain methods H04N1/32309 takes precedence
• CPC Class Codes: H04N 1/32229 with selective or adaptive application of the additional information, e.g. in selected regions of the image H04N1/32213 takes precedence
• CPC Class Codes: H04N 2005/91335 the copy protection signal being a watermark
• 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 5/913 for scrambling ; for copy protection
• CPC Class Codes: H04N 7/025 Systems for the transmission of digital non-picture data, e.g. of text during the active part of a television frame transmission of digital non-picture data during the vertical blanking interval only H04N7/088
• CPC Class Codes: H04N 7/035 Circuits for the digital non-picture data signal, e.g. for slicing of the data signal, for regeneration of the data-clock signal, for error detection or correction of the data signal
• 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

Abstract

A specific frequency extraction unit extracts a specific frequency component signal from an input image signal, a phase controller and amplitude controller control at least one of the phase and amplitude of the specific frequency component signal in accordance with watermark information, and a watermark information superposition unit superposes the specific frequency component signal on the input image signal to generate an image signal embedded with the watermark information.

Claims

1. A digital watermark embedding method of embedding watermark information in an image signal, comprising:

extracting a specific frequency component signal from the input image signal;

controlling at least one of a phase and amplitude of the specific frequency component signal in accordance with the watermark information; and

outputting an image signal embedded with the watermark information by superposing the specific frequency component signal, at least one of the phase and amplitude of which has been controlled, on the input image signal.

2. The digital watermark embedding method according to claim 1, further comprising limiting an amplitude of the specific frequency signal.

3. The digital watermark embedding method according to claim 1, wherein extraction of the specific frequency component signal is randomized.

4. The digital watermark embedding method according to claim 1, wherein outputting the image signal comprises subjecting the specific frequency component signal, at least one of the phase and amplitude of which has been controlled, to a nonlinear process, and superposing the specific frequency component signal processed on the image input signal.

5. A digital watermark detection method comprising:

extracting a specific frequency component signal from an input image signal in which watermark information is embedded;

controlling at least one of a phase and amplitude of the specific frequency component signal extracted, to obtain a controlled specific frequency component signal; and

performing a correlation operation between the controlled specific frequency component signal and the input image signal to extract the watermark information.

6. The digital watermark detection method according to claim 5, further comprising limiting an amplitude of the specific frequency signal.

7. The digital watermark detection method according to claim 5, further comprising randomizing the specific frequency component signal extracted.

8. The digital watermark detection method according to claim 5, wherein performing the correlation comprises subjecting the controlled specific frequency component signal to a nonlinear process, and performing the correlation operation between the image input signal and the controlled specific frequency component signal subjected to the nonlinear process.

9. A digital watermark embedding apparatus which embeds watermark information in an input image signal, comprising:

an extraction unit configured to extract a specific frequency component signal from the input image signal;

a control unit configured to control at least one of a phase and amplitude of the extracted specific frequency component signal in accordance with the watermark information; and

a superposing unit configured to superpose the specific frequency component signal, at least one of the phase and amplitude of which has been controlled by the control unit, on the input image signal to output an image signal embedded with the watermark information.

10. The digital watermark embedding apparatus according to claim 9, further comprising an amplitude limiter which is inserted between the extraction unit and the superposing unit and limits an amplitude of the specific frequency signal.

11. The digital watermark embedding apparatus according to claim 9, wherein a characteristic of at least one of the extraction unit and the control unit is randomized using randomizing information.

12. The digital watermark embedding apparatus according to claim 9, further comprising a nonlinear filter inserted between the control unit and the superposing unit.

18. A digital watermark embedding apparatus according to claim 9, further comprising an amplitude limiter which is inserted between the extraction means and the superposing means and limits an amplitude of the specific frequency signal.

19. A digital watermark embedding apparatus according to claim 9, further comprising a nonlinear filter inserted between the control means and the superposing means.

13. A digital watermark detection apparatus which detects watermark information embedded in an input image signal, comprising:

an extraction unit configured to extract a specific frequency component signal from the input image signal;

a control unit configured to control at least one of a phase and amplitude of the specific frequency component signal extracted; and

a correlation computing unit configured to perform a correlation operation between the specific frequency component signal, at least one of the phase and amplitude of which has been controlled by the control unit, and the input image signal, to extract the watermark information.

14. The digital watermark detection apparatus according to claim 13, further comprising an amplitude limiter which is inserted between the extraction unit and the correlation computing unit and limits an amplitude of the specific frequency signal.

15. The digital watermark detection apparatus according to claim 13, wherein a characteristic of at least one of the extraction unit and the control unit is randomized using randomizing information.

16. The digital watermark detection apparatus according to claim 13, further comprising a nonlinear filter inserted between the control unit and the correlation computing unit.

17. A digital watermark embedding apparatus comprising:

extraction means for extracting a specific frequency component signal from an input image signal;

control means for controlling at least one of a phase and amplitude of the extracted specific frequency component signal in accordance with watermark information; and

superposing means for superposing the specific frequency component signal, at least one of the phase and amplitude of which has been controlled by the control means, on the input image signal so as to output an image signal embedded with the watermark information.

20. A digital watermark detection apparatus comprising:

extraction means for extracting a specific frequency component signal from an input image signal in which watermark information is embedded;

control means for controlling at least one of a phase and amplitude of the extracted specific frequency component signal; and

correlation computing means for performing a correlation operation between the specific frequency component signal, at least one of the phase and amplitude of which has been controlled by the control means, and the input image signal, to extract the watermark information.