Audio watermarking with dual watermarks

• US 6,952,774 B1
• Filed: 05/22/1999
• Issued: 10/04/2005
• Est. Priority Date: 05/22/1999
• Status: Expired due to Fees

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Kirovski, Darko, Malvar, Henrique, Jakubowski, Mariusz H.
• Primary Examiner(s): Barron, Gilberto
• Assistant Examiner(s): MEISLAHN, DOUGLAS J
• Application Number:
  US09/316,899
• Time in Patent Office: 2,327 Days
• Field of Search: 713/176, 382/100
• US Class Current: 713/176
• CPC Class Codes: G11B 20/00086 Circuits for prevention of unauthorised reproduction or copying, e.g. piracy indicating unauthorised use of record carriers in general G11B23/28; scrambling for television signal recording H04N5/913; network architectures or network protocols for network security H04L63/00; cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
• CPC Class Codes: G11B 20/00891 embedded in audio data
• CPC Class Codes: G11B 2020/1062 Data buffering arrangements, e.g. recording or playback buffers
• CPC Class Codes: H04H 20/31 using in-band signals, e.g. subsonic or cue signal
• CPC Class Codes: H04N 2005/91335 the copy protection signal being a watermark

Abstract

A watermark encoding system encodes an audio signal with both a strong and a weak watermark. The strong watermark identifies the content producer and is designed to survive all typical kinds of processing and malicious attacks. The weak watermark identifies the content as an original and is designed to be significantly removed as a result of most normal signal processing (other than A/D and D/A). The watermark encoding system has a converter to convert an audio signal into frequency and phase components and a mask processor to determine a hearing threshold for corresponding frequency components. The watermark encoding system also has a pattern generator to generate both the strong and weak watermarks and a watermark insertion unit to selectively insert either the strong or weak watermark into the audio signal. The watermark insertion unit adds the strong watermark to the audio signal when the signal exceeds the hearing threshold by a buffer value (e.g., 1-8 dB) and adds the weak watermark insertion unit when the signal falls below the hearing threshold by the buffer value. When the signal falls within the buffer area about the hearing threshold, the insertion unit takes no action. A watermark detecting system is equipped with a watermark detector that determines which block interval of the watermarked audio signal contains a watermark pattern and if the strong or weak watermark is present in that block interval of the signal.

Claims

1. An audio watermarking system comprising:

a pattern generator to generate both a strong watermark and a weak watermark; and

a watermark insertion unit to insert the strong watermark and the weak watermark into the audio signal,

wherein the watermark insertion unit selectively inserts either the strong watermark or the weak watermark into segments of the signal according to an audible measure of the segments.

2. An audio watermarking system comprising:

a pattern generator to generate both a strong watermark and a weak watermark;

a watermark insertion unit to insert the strong watermark and the weak watermark into the audio signal;

a processor to determine a hearing threshold for the audio signal; and

the watermark insertion unit inserts the strong watermark when the signal exceeds the hearing threshold and inserts the weak watermark when the signal falls below the hearing threshold.

3. An audio watermarking system comprising:

a pattern generator configured to generate both a strong watermark and a weak watermark; and

a watermark insertion unit configured to insert the strong watermark into one or more first segments of the audio signal and to insert the weak watermark into one or more second segments of the audio signal, wherein the first and second segments are separate, wherein the watermark insertion unit selectively chooses segments for insertion of the weak watermark according to an audible measure of the segments.

4. An audio watermarking system comprising:

a pattern generator to generate both a strong watermark and a weak watermark; and

a watermark insertion unit to insert the strong watermark and the weak watermark into the audio signal,

wherein the watermark insertion unit selectively inserts either the strong watermark or the weak watermark into segments of the signal according to an audible measure of the segments.

5. An audio watermark encoding system comprising:

a converter to convert an audio signal into magnitude and phase components;

a mask processor to determine a hearing threshold for corresponding magnitude components;

a pattern generator to generate both a strong watermark and a weak watermark; and

a watermark insertion unit to selectively insert one of either the strong watermark or the weak watermark into the audio .signal based on whether the magnitude components exceed or fall below the hearing threshold.

6. An audio watermark encoding system as recited in claim 5, wherein the watermark insertion unit inserts the strong watermark when the magnitude component exceeds the hearing threshold and inserts the weak watermark when the magnitude component falls below the hearing threshold.

7. An audio watermark encoding system as recited in claim 5, wherein the watermark insertion unit inserts the strong watermark when the magnitude component exceeds the hearing threshold by a predetermined amount and inserts the weak watermark when the magnitude component falls below the hearing threshold by the predetermined amount.

8. An audio watermark encoding system as recited in claim 5, wherein the watermark insertion unit foregoes inserting the strong watermark or the weak watermark when the magnitude component lies within the predetermined amount above and below the hearing threshold.

9. An audio encoding system comprising:

an audio watermark encoding system as recited in claim 5; and

a compression unit, wherein the compression unit and the audio watermark encoding system both utilize the magnitude components.

10. An operating system comprising an audio watermark encoding system as recited in claim 5.

11. A watermark insertion unit, comprising:

an input to receive frequency magnitude components of an audio signal, hearing thresholds derived from the magnitude components, strong watermark values, and weak watermark values; and

multiple insertion operators for selectively combining the magnitude components and one of either the strong watermark values or the weak watermark values depending upon whether the magnitude components exceed or fall below the hearing thresholds.

12. An audio decoding system comprising:

an audio watermark detection system comprising;

a pattern generator configured to generate both a strong watermark and a weak watermark; and

a watermark detector configured to detect whether a watermark is present in a portion of the watermarked audio signal and, if a watermark is detected, further configured to determine whether that watermark is either a strong or a weak watermark;

a converter configured to convert a watermarked audio signal into magnitude and phase components;

a mask processor configured to determine a hearing threshold for corresponding magnitude components; and

a decompression unit, wherein the decompression unit and the audio watermark detection system both utilize the magnitude components.

13. An audio watermarking architecture comprising:

a watermark encoding system configured to selectively insert either a strong watermark or a weak watermark into segments of an audio signal; and

a watermark detecting system configured to detect a presence of either the strong watermark or the weak watermark in the segments of the audio signal

wherein the watermark encoding system comprises;

a converter configured to convert the audio signal into magnitude and phase components;

a mask processor configured to determine a hearing threshold for corresponding magnitude components;

a pattern generator configured to generate both the strong watermark and the weak watermark; and

a watermark configured insertion unit to selectively insert one of either the strong watermark or the weak watermark into the audio signal based on whether the magnitude components exceed or fall below the hearing threshold.

14. A method for watermarking an audio signal, comprising:

comparing samples of the audio signal to a hearing threshold;

watermarking samples exceeding the hearing threshold with a strong watermark; and

watermarking samples falling below the hearing threshold with a weak watermark.

15. A method as recited in claim 14, wherein the watermarking samples comprises:

watermarking samples exceeding the hearing threshold plus a buffer value with a strong watermark;

watermarking samples falling below the hearing threshold by less than the buffer value a with a weak watermark; and

leaving samples lying within the buffer value above and below the hearing threshold without a watermark.

16. A method as recited in claim 14, further comprising detecting the strong watermark and the weak watermark in the audio signal.

17. A method as recited in claim 14, wherein the detecting comprises computing a correlation value from the audio signal and the strong watermark, the correlation value tending toward a first value when the strong watermark is present and a second value when the strong watermark is not present.

18. A method as recited in claim 14, wherein the detecting comprises computing a correlation value from the audio signal and the weak watermark, the correlation value tending toward a first value when the weak watermark is present and a second value when the weak watermark is not present.

19. A method as recited in claim 14, further comprising:

computing a correlation value from the audio signal and one of the strong watermark or the weak watermark; and

determining that said one strong watermark or weak watermark is present when the correlation value exceeds a predetermined threshold plus a random amount.

20. A method as recited in claim 14, further comprising:

computing a correlation value from the audio signal and one of either the strong watermark or the weak watermark; and

determining that either said one strong watermark or said one weak watermark is present when the correlation value exceeds a predetermined threshold plus a random amount.

21. A computer readable medium having computer executable instructions for:

comparing samples of an audio signal to a hearing threshold;

watermarking samples exceeding the hearing threshold with a strong watermark; and

watermarking samples falling below the hearing threshold with a weak watermark.

22. An audio watermarking system comprising:

a pattern generator configured to generate both a strong watermark and a weak watermark; and

a watermark insertion unit configured to insert the strong watermark into one or more first segments of the audio signal and to insert the weak watermark into one or more second segments of the audio signal, wherein the first and second segments are separate;

a processor configured to determine a hearing threshold for segments of the audio signal; and

the watermark insertion unit being further configured to insert the strong watermark into a segment when the signal of that segment exceeds the hearing threshold and inserts the weak watermark into a segment when the signal of that segment falls below the hearing threshold.

23. An audio watermark detection system, comprising:

an input module configured to receive a watermarked audio signal;

a synchronization module configured to determine which portion of the watermarked audio signal might contain a watermark; and

a correlation module configured to detect whether a watermark is present in the portion of the watermarked audio signal that the synchronization module determines might contain a watermark and, if a watermark is detected, further configured to determine whether that watermark is either a strong watermark or a weak watermark.

24. An audio watermark detection system as recited in claim 23, wherein the correlation module is further configured to compute a correlation value from the watermarked audio signal and the strong watermark that tends toward a first value when the strong watermark is present and a second value when the strong watermark is not present.

25. An audio watermark detection system as recited in claim 23, wherein the correlation module is further configured to compute a correlation value from the watermarked audio signal and the weak watermark that tends toward a first value when the weak watermark is present and a second value when the weak watermark is not present.

26. An audio watermark detection system as recited in claim 23, wherein the correlation module is further configured to compute a correlation value from the watermarked audio signal and one of either the strong watermark or the weak watermark, the correlation module determining that said one strong watermark or weak watermark is present when the correlation value exceeds a predetermined threshold plus a random amount.

27. An operating system comprising an audio watermark detection system as recited in claim 23.

28. An audio watermark detection system comprising:

a pattern generator configured to generate both a strong watermark and a weak watermark; and

a watermark detector configured to detect whether a watermark is present in a portion of the watermarked audio signal and, if a watermark is detected, further configured to determine whether that watermark is either a strong or a weak watermark;

a random operator for generating a random value; and

the watermark detector being further configured to compute correlation values from the watermarked audio signal and each of the strong watermark and the weak watermark and to determine whether that watermark is either the strong watermark or the weak watermark based on whether the correlation values exceed a predetermined threshold plus the random value.

29. An audio watermark detection system comprising:

a pattern generator configured to generate both a strong watermark and a weak watermark; and

a watermark detector configured to detect whether a watermark is present in a portion of the watermarked audio signal and, if a watermark is detected, further configured to determine whether that watermark is either a strong or a weak watermark,

wherein the watermark detector is further configured to compute correlation values from the watermarked audio signal and each of the strong watermark and the weak watermark and to determine whether that watermark is either the strong watermark or the weak watermark based on whether the correlation values exceed a predetermined threshold.

30. An audio watermarking architecture comprising:

a watermark encoding system configured to selectively insert either a strong watermark or a weak watermark into segments of an audio signal; and

a watermark detecting system configured to detect a presence of either the strong watermark or the weak watermark in the segments of the audio signal

wherein the watermark detecting system comprises;

a converter configured to convert a watermarked audio signal into magnitude and phase components;

a mask processor configured to determine a hearing threshold for corresponding magnitude components;

a pattern generator configured to generate both a strong watermark and a weak watermark; and

a watermark detector configured to detect whether a watermark is present in a portion of the watermarked audio signal and, if a watermark is detected, further configured to determine whether that watermark is either the strong or the weak watermark.