Watermarking Employing the Time-Frequency Domain

• US 20080181449A1
• Filed: 02/12/2008
• Published: 07/31/2008
• Est. Priority Date: 09/14/2000
• Status: Active Grant

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Levy, Kenneth L., Hannigan, Brett T.
• Granted Patent: US 7,711,144 B2
• Time in Patent Office: Days
• US Class Current: 382/100
• CPC Class Codes: G06T 1/0028 Adaptive watermarking, e.g. Human Visual System [HVS]-based watermarking
• CPC Class Codes: G06T 2201/0052 Embedding of the watermark in the frequency domain
• CPC Class Codes: H04N 19/467 characterised by the embedded information being invisible, e.g. watermarking
• 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

Abstract

Methods and systems for watermarking of signals employ time frequency analysis. An encoding method divides the signal into segments, transforms each segment into a time-frequency representation, and computes a time-frequency domain watermark signal based on the time frequency representation. It then combines the time-frequency domain watermark signal with the media signal to produce a watermarked media signal. To embed a message using this method, one may use peak modulation, pseudorandom noise modulation, statistical feature modulation, etc. Watermarking that uses a time-frequency representation enables the encoder to adapt and or derive the modifications made to embed data based on the time frequency representation.

Claims

1. A method of watermarking an audio signal, the method comprising:

performing frequency transformations of blocks of audio to produce frequency domain representations of the blocks;

forming a two dimensional representation of the audio from the frequency domain representations;

providing an auxiliary data signal to be embedded in the audio signal; and

modifying the two dimensional representation of the audio according to the auxiliary data signal to embed the auxiliary data signal in the audio signal.

2. The method of claim 1 wherein the modifying includes computing changes to the audio signal to encode the auxiliary data based on the two dimensional representation of the audio that includes both time and frequency dimensions.

3. The method of claim 1 wherein the modifying includes performing a two dimensional transformation of the two dimensional representation of the audio.

4. The method of claim 3 wherein the two dimensional transformation is dependent on the auxiliary data signal to be embedded in the audio signal.

5. The method of claim 1 wherein the modifying includes varying a function used to represent a message symbol of the auxiliary data with frequency, such that the same message symbol is represented differently at different frequencies.

6. The method of claim 5 wherein varying includes varying a direction of a modulation of the two dimensional representation.

7. The method of claim 1 wherein the modifying comprises modifying regions in the two dimensional representation to correspond to elements of the auxiliary data.

8. The method of claim 7 wherein the modifying the regions comprises setting values within the regions to correspond to elements of the auxiliary data, the values being set in a signal dependent manner.

9. The method of claim 1 wherein the modifying includes computing a modification from the two dimensional representation and applying the computed modification to the audio signal in a different domain.

10. The method of claim 9 wherein the different domain comprises a frequency domain of the audio signal.

11. The method of claim 9 wherein the different domain comprises a time domain of the audio signal.

12. A method of watermarking an audio signal, the method comprising:

performing frequency transformations of blocks of audio to produce frequency domain representations of the blocks;

forming a two dimensional representation of the audio from the frequency domain representations;

providing an auxiliary data signal to be embedded in the audio signal; and

from the two dimensional representation of the audio, deriving modifications of the audio signal that correspond to the auxiliary data signal and applying the modifications to the audio signal to embed the auxiliary data signal in the audio signal.

13. A computer readable medium on which is stored instructions, which, when executed by a computer, perform a method of watermarking an audio signal, the method comprising:

performing frequency transformations of blocks of audio to produce frequency domain representations of the blocks;

forming a two dimensional representation of the audio from the frequency domain representations;

providing an auxiliary data signal to be embedded in the audio signal; and

modifying the two dimensional representation of the audio according to the auxiliary data signal to embed the auxiliary data signal in the audio signal.

14. A method of decoding an auxiliary data signal from an audio signal, the method comprising:

performing frequency transformations of blocks of audio to produce frequency domain representations of the blocks;

forming a two dimensional representation of the audio from the frequency domain representations;

analyzing the two dimensional representation of the audio signal to ascertain modifications made to encode the auxiliary data signal; and

reading the auxiliary data signal from the modifications.

15. A computer readable medium on which is stored instructions, which, when executed by a computer, perform a method of decoding an auxiliary data signal from an audio signal, the method comprising:

performing frequency transformations of blocks of audio to produce frequency domain representations of the blocks;

forming a two dimensional representation of the audio from the frequency domain representations;

analyzing the two dimensional representation of the audio signal to ascertain modifications made to encode the auxiliary data signal; and

reading the auxiliary data signal from the modifications.