Watermarking of recordings

• US 20050226461A1
• Filed: 03/11/2005
• Published: 10/13/2005
• Est. Priority Date: 03/12/2004
• Status: Active Grant

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Briancon, Alain Charles Louis, Carlton, Alan Gerald, Chitrapu, Prabhakar R., Goldberg, Steven Jeffrey, Herschaft, Richard Dan
• Granted Patent: US 7,190,808 B2
• Time in Patent Office: Days
• US Class Current: 382/100
• CPC Class Codes: G06T 1/0021 Image watermarking
• CPC Class Codes: G10L 19/018 Audio watermarking, i.e. embedding inaudible data in the audio signal

Abstract

Signals encoded with watermark information are generated and broadcast into a protected area for capture by illicit recording devices along with their intended targets. An illicit recording in which at least a portion of the broadcast watermark signals are recorded is obtained and correlated with a known position of the broadcast watermark signals to yield the location of illicit recording devices. In an alternate embodiment, a surveillance device, being image and time synchronized with a signal broadcasting device, monitors and records the protected area. Illicit recordings containing the broadcast watermark are obtained and correlated with corresponding recordings taken by the surveillance device to identify the location of illicit recording devices. In an alternate embodiment, the surveillance device further monitors the quality of the broadcast watermark signals and adjusts them accordingly to achieve a desired quality level.

Claims

1. A method for locating a recorder in a protected area, the method comprising:

(a) generating a signal encoded with watermark information;

(b) broadcasting the watermark signal into a protected area;

(c) obtaining a recording in which at least a portion of the broadcast watermark signal is recorded; and

(d) correlating the recorded portion of the watermark signal with a known position of the broadcast watermark signal.

2. The method of claim 1 wherein step (b) further comprises broadcasting a watermark signal that is difficult to distinguish from noise by humans.

3. The method of claim 1 wherein step (b) further comprises broadcasting the watermark signal in front of a protected target using a mobile device attached to the target, said watermark signal being extractable from a recording of said target using an extraction algorithm.

4. The method of claim 1 wherein step (b) further comprises redundantly broadcasting the watermark signal throughout the protected area such that a recording of said protected area includes a plurality of non-obstructed portions of the broadcast watermark signal, said plurality of signal portions being selectively combined to determine said watermark information.

5. The method of claim 1 wherein step (b) further comprises redundantly spreading the broadcast watermark signal across a wide area in the protected area using high redundancy coding such that said watermark information is extractable from a recording of said protected area via an error correction technique.

6. The method of claim 1 wherein step (a) further comprises encoding the watermark signal with current time, date, and location information.

7. The method of claim 1 wherein step (b) further comprises updating by simultaneously broadcasting a watermark signal encoded with updated watermark information and a watermark signal encoded with previously current watermark information.

8. The method of claim 1 wherein step (a) further comprises encoding the watermark signal with bar coded information.

9. The method of claim 1 wherein step (b) further comprises using time reversal audio to broadcast audio watermark signals.

10. The method of claim 1 wherein electromagnetic signals are encoded with watermark information and broadcast into a protected area such that a recording of said protected area includes a combination of watermark signals, said signals being broadcast from a plurality of sources positioned throughout the protected area.

11. The method of claim 10 wherein the signals are generated in a light frequency band.

12. The method of claim 10 wherein the signals are generated in an ultraviolet or infrared frequency band.

13. The method of claim 10 wherein the signals are encoded with watermark information by varying the frequencies of said signals in a predetermined manner.

14. The method of claim 10 wherein the signals are encoded with watermark information by varying the amplitude of said signals in a predetermined manner.

15. The method of claim 10 wherein the signals are encoded with watermark information by varying the phase distance between said signals in a predetermined manner.

16. The method of claim 10 wherein the signals are redundancy encoded with watermark information such that said watermark information is extractable from a recording of said protected area via an error correction technique.

17. The method of claim 10 wherein the signals are broadcast across a wide area in the protected area using high redundancy coding such that said watermark information is extractable from a recording of said protected area via an error correction technique.

18. The method of claim 1 wherein step (a) further comprises:

(a1) generating a fundamental watermark signal encoded with basic watermark information; and

(a2) generating an advanced watermark signal encoded with advanced watermark information, said advanced information being detectable by recording devices with advanced recording functionality;

and

wherein step (b) further comprises broadcasting fundamental and advanced watermark signals into a protected area.

19. A method for broadcasting a watermark into a protected area, the method comprising:

(a) sensing atmospheric conditions in a protected area;

(b) generating a watermark signal having a desired quality level based on the atmospheric conditions;

(c) broadcasting the watermark signal into the protected area;

(d) monitoring the quality level of the broadcast watermark signal; and

(e) adjusting the watermark signal to maintain the desired quality level.

20. The method of claim 19 wherein the watermark signals are electromagnetic signals encoded by varying a combination of the signals'"'"' frequencies, amplitudes, and phase distances.

21. The method of claim 19 wherein the watermark signals are audio signals encoded by varying a combination of the signals'"'"' frequencies, amplitudes, and phase distances.

22. The method of claim 19 wherein the quality level of the watermark signal is defined in terms of fidelity and robustness.

23. The method of claim 19 further comprising:

(d1) extracting the broadcast watermark signal from the protected area;

(e1) iteratively increasing the robustness of the watermark signal if the extracted watermark signal has errors; and

(e2) iteratively decreasing the robustness of the watermark signal if the extracted watermark is without errors.

24. The method of claim 19 wherein step (a) further comprises:

(a1) broadcasting probing signals into the protected area to determine the atmospheric conditions in the protected area.

25. The method of claim 19 wherein the watermark is broadcast by a signal broadcasting device operated by a protected target.

26. The method of claim 19 wherein step (c) further comprises:

(c1) broadcasting the watermark signal onto a vapor screen in front of the protected area.

27. The method of claim 19 wherein the watermark signal is encoded with metadata, said metadata being entered into a processor for encoding via a keypad, a voice recognition device, an input/output connection, or remotely through a wireless network.

28. The method of claim 27 wherein the metadata is encrypted.