System and method of watermarking signal

• US 7,146,503 B1
• Filed: 03/26/2002
• Issued: 12/05/2006
• Est. Priority Date: 06/04/2001
• Status: Active Grant

• Current Assignee: AT&T Corporation (AT&T, Inc.)
• Original Assignee: AT&T Corporation (AT&T, Inc.)
• Inventors: Johnston, James David, Kuo, Shyh-Shiaw, Turin, William, Quackenbush, Schuyler Reynier
• Primary Examiner(s): Barroń, Jr., Gilberto
• Assistant Examiner(s): Nguyen, Minh Dieu
• Application Number:
  US10/107,083
• Time in Patent Office: 1,715 Days
• Field of Search: 713/176, 380200-201, 380218-221, 380/216, 380237-238, 380250-252, 382/100, 382/232, 704/203, 704/500
• US Class Current: 713/176
• CPC Class Codes: G10L 19/018 Audio watermarking, i.e. embedding inaudible data in the audio signal
• CPC Class Codes: G10L 19/022 Blocking, i.e. grouping of samples in time; Choice of analysis windows; Overlap factoring
• CPC Class Codes: G11B 20/00891 embedded in audio data

Abstract

A system and method of generating a watermarked signal are disclosed. The system segments the signal into overlapping blocks using a window function and processes the overlapping blocks according to whether each block is odd- or even-numbered. The system windows the odd-numbered blocks, modulates the phase of each block in the frequency domain, transforms each modulated block in the time domain, windows each block transformed into the time domain and overlap-adds each odd-numbered block with each even-numbered block to generate the watermarked signal.

Claims

1. A method of generating a watermarked signal, the method comprising:

(1) segmenting the signal into overlapping blocks using a window function;

(2) for odd-numbered blocks, windowing each block using the window function; and

(3) for even-numbered blocks;

(a) transforming each block into a frequency domain;

(b) modulating a phase of each block in the frequency domain by constraining the phase change inside a critical band to prevent an audible envelope change in a time signal;

(c) transforming each modulated block in a time domain;

(d) windowing each block transformed into the time domain; and

(4) overlap-adding each odd-numbered block with each even-numbered block to generate the watermarked signal.

2. The method of generating a watermarked signal of claim 1, the method further comprising, when modulating each block:

adding redundancy using error-correcting codes.

3. The method of generating a watermarked signal of claim 2, the method further comprising:

using convolutional codes when modulating each block.

4. The method of generating a watermarked signal of claim 3, the method further comprising:

using block code when modulating the phase of each block.

5. The method of generating a watermarked signal of claim 4, the method further comprising:

interleaving when modulating each block.

6. The method of generating a watermarked signal of claim 1, wherein modulating the phase of each even-numbered block is accomplished according to the following equation:

{overscore (S)}_k(f)=S_k(f)·

e<sup>jΦ

k(f)</sup>, f=0, . . . , N−

1,

wherein f is in Hz, k is the number of the block, Φ

_k(b)=a<sub>i−

1</sub>ø

(b−

(i−

1))+a_iø

(b−

1), for i−

1≦

b≦

1, and b=13 arctan (0.76f/1000)+3.5 arctan((f/77500)²).

7. A method of adding message bits to a signal, the method comprising:

(1) segmenting the signal into overlapping blocks using a window function;

(2) for odd-numbered blocks;

(a) windowing each block using the window function; and

(3) for even-numbered blocks;

(a) in a frequency domain, embedding a message bit into every integer bark-scale bin for each block, wherein a phase modulation for a k-th block is;

Φ

_k(b)=Σ

a_iø

(b−

i), 0.0≦

b≦

I, for i=1 to I, where I is the maximum bark

scale for embedding watermark;

(b) overlapping and adding adjacent window functions wherein the phase modulation for an i-th bark-scale bin is;

Φ

_k(b)=a<sub>i−

1</sub>ø

(b−

(i−

1))+a_iø

(b−

i), for i−

1≦

b<

i;

(c) modulating a phase of each block on a bark scale, wherein each integer bark scale bin carries a message bit;

(d) transforming each modulated block in a time domain;

(e) windowing each block transformed into the time domain; and

(4) overlap-adding each odd-numbered block with each even-numbered block to generate a watermarked signal.

8. The method of adding message bits to a signal of claim 7, wherein embedding a message bit into each bark scale bin of the block further comprises representing each message bit by a phase window function centered at the end of a corresponding bark band and spanning two adjacent barks.

9. The method of adding message bits to a signal of claim 7, wherein modulating the phase of each block is accomplished according to the following:

{overscore (S)}_k(f)=S_k(f)·

e<sup>jΦ

k(f)</sup>, f=0, . . . , N−

1, where f is the frequency in Hz.

10. A method of generating a watermarked signal from a signal, the method comprising:

(1) segmenting the signal into overlapping blocks s_k(n), n=0, . . . , N−

1 using a window function;

(2) for odd-numbered blocks;

(a) windowing each block using the window function to generate blocks s*_k(n); and

(3) for even-numbered blocks;

(a) in a frequency domain, embedding a message bit into every integer bark-scale bin for each even-numbered block S_k(f), wherein a phase modulation for a k-th block is;

Φ

_k(b)=Σ

a_iø

(b−

i), 0.0≦

b≦

I, where b=13 arctan (0.76f/1000)+3.5

arctan((f/7500)²) and where the resulting signal for each even-numbered block is;

{overscore (S)}_k(f)=S_k(f)·

e<sup>jΦ

k(f)</sup>, f=0, . . . , N−

1;

(b) in a time domain, windowing the phase modulated block to generate {overscore (s)}*_k(n); and

(4) overlapping and adding {overscore (s)}*_k(n) and s*_k(n).

11. The method of generating a watermarked signal of claim 10, wherein the signal is an audio signal.

12. The method of generating a watermarked signal of claim 10, further comprising repeating each message bit for redundancy.

13. A method of generating a watermarked signal from a signal, the method comprising:

(1) windowing the signal into overlapping windowed blocks Sk(n), n=0, . . . , N−

1 using a window function;

(2) windowing each odd block to generate s*_k(n), n=0, . . . , N−

1, k=1, 3 . . . odd numbers;

(3) for each even block s_k(n), n=0, . . . , N−

1, k=0, 2 . . . even numbers;

(a) transforming s_k(n) into a frequency domain as S_k(f);

(b) phase modulating s_k(f) in the frequency domain to generate {overscore (S)}_k(f) and applying a message bit to the integer bark scale associated with each block S_k(f), wherein the phase modulation for a k-th block is;

Φ

_k(b)=Σ

a_iø

(b−

i), 0.0≦

b≦

I, where I is a maximum bark scale for embedding the watermark;

(c) transforming S_k(f) into a time domain to generate {overscore (s)}_k(n);

(d) windowing {overscore (s)}_k(n) in the time domain to generate {overscore (s)}*_k(n); and

(4) overlap-adding the odd and even blocks to form the watermarked signal.

14. The method of claim 13, wherein phase modulating S_k(f) in the frequency domain to generate {overscore (S)}_k(f) further comprises complying with the following rule:

|(dΦ

/d b)|<

30°

, where Φ

is the signal phase, and b is the bark scale.

15. The method of claim 13, wherein N is at least 2¹⁴.

16. The method of claim 15, wherein, for the even blocks, phase modulating S_k(f) comprises generating {overscore (S)}_k(f) according to the following:

{overscore (S)}_k(f)=S_k(f)·

e<sup>jΦ

k(f)</sup>, f=0, . . . , N−

1, where is in Hz.

17. The method of claim 13, wherein the relation of f to the bark scale is b=13 arctan (0.76f/1000)+3.5 arctan((f/7500)²).

18. The method of claim 13, further comprising representing each message bit by a phase window function centered at the end of a corresponding bark band and that spans two adjacent bark bands, the phase window function being defined as:

Φ

(b)=sin²(π

(b+1)/2), −

1.0≦

b≦

1.0.

19. The method of claim 13, further comprising adding and overlapping adjacent window functions to generate a final phase modulation in the i-th bark scale bin according to:

Φ

_k(b)=a<sub>i−

1</sub>ø

(b−

(i−

1))+a_iø

(b−

1), for i−

1≦

b≦

i.

20. The method of claim 13, further comprising modifying the phases of the k-th audio block according to:

Φ

_k(b)=Σ

a_iø

(b−

i), 0.0≦

b≦

I.

21. A method of generating a watermarked signal from a signal, the method comprising:

(1) segmenting the signal into overlapping blocks using a window function;

(2) for odd-numbered blocks;

(a) windowing each block using the window function to generate odd-numbered windowed blocks; and

(3) for even-numbered blocks;

(a) in a frequency domain, embedding a message bit into every integer bark-scale bin for each even-numbered block, wherein the phase modulation for a k-th block is Φ

_k(b)=Σ

a_iø

(b−

i) and |(dø

|d b)|<

30°

, where ø

is the signal phase, and b is the bark scale; and

(b) in a time domain, windowing the phase-modulated block; and

(4) overlapping and adding the odd-numbered windowed blocks and even-numbered phase-modulated blocks.

22. The method of generating a watermarked signal of claim 21, wherein the signal is an audio signal.

23. The method of generating a watermarked signal of claim 21, further comprising repeating each message bit for redundancy.

24. The method of generating a watermarked signal of claim 21, wherein for the phase modulation of the k-th block Φ

_k(b)=Σ

a_iø

(b−

i), and 0.0≦

b≦

I.

25. A method of generating a watermarked signal from a signal that is segmented into overlapping blocks using a window function and where odd-numbered blocks are windowed using the window function, the method comprising, for even-numbered blocks:

(a) determining whether an audibility rule is met; and

(b) if the audibility rule is met, embedding a message bit into every integer bark-scale bin for each even-numbered block, wherein if the audibility rule is met, the phase modulation for the k-th even-numbered block is Φ

_k(b)=Σ

a_iø

(b−

i), where ø

is the signal phase, and b is the bark scale.

26. The method of generating a watermarked signal of claim 25, wherein the audibility rule is |(dø

|d b)|<

30°

.

27. The method of generating a watermarked signal of claim 26, further comprising:

windowing each phase-modulated block; and

overlapping and adding the odd-numbered windowed blocks and even-numbered phase-modulated blocks to generate the watermarked signal.

28. A method of generating a watermarked signal from a signal that is segmented into overlapping blocks using a window function, the method associated with using the segmented blocks to perform phase modulation of even-numbered blocks and overlap-adding the even-numbered blocks and odd-numbered blocks to generate the watermarked signal, the method comprising:

(a) determining whether an audibility rule is met; and

(b) if the audibility rule is met, embedding a message bit into every integer bark-scale bin for each even-numbered block, wherein if the audibility rule is met, the phase modulation for the k-th even-numbered block is Φ

_k(b)=Σ

a_iø

(b−

i), where ø

is the signal phase, and b is the bark scale.

29. The method of generating a watermarked signal of claim 28, wherein the audibility rule is |(dø

|d b)|<

30°

.