Digital watermarking

• US 6,725,372 B1
• Filed: 12/02/1999
• Issued: 04/20/2004
• Est. Priority Date: 12/02/1999
• Status: Expired due to Term

• Current Assignee: Verizon Laboratories Incorporated (Verizon Communications Inc.)
• Original Assignee: Verizon Laboratories Incorporated (Verizon Communications Inc.)
• Inventors: Basch, Evert, Lewis, Arianne M.
• Primary Examiner(s): Barrón, Gilberto
• Assistant Examiner(s): McArdle, Joseph M
• Application Number:
  US09/453,333
• Time in Patent Office: 1,601 Days
• Field of Search: 713/176, 382/100, 380/210, 380/201, 380/202, 380/203
• US Class Current: 713/176
• CPC Class Codes: G06T 1/0035 Output size adaptive watermarking
• CPC Class Codes: G06T 2201/0051 Embedding of the watermark in the spatial domain
• CPC Class Codes: G06T 2201/0052 Embedding of the watermark in the frequency domain
• CPC Class Codes: G06T 2201/0053 Embedding of the watermark in the coding stream, possibly without decoding; Embedding of the watermark in the compressed domain
• CPC Class Codes: G06T 2201/0061 Embedding of the watermark in each block of the image, e.g. segmented watermarking
• 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 1/32277 Compression
• CPC Class Codes: H04N 19/467 characterised by the embedded information being invisible, e.g. watermarking
• CPC Class Codes: H04N 19/48 using compressed domain processing techniques other than decoding, e.g. modification of transform coefficients, variable length coding [VLC] data or run-length data motion estimation in a transform domain H04N19/547; processing of decoded motion vectors H04N19/513
• CPC Class Codes: H04N 19/61 in combination with predictive coding

Abstract

The invention is a system for digital watermarking that operates on a conventional digital video stream to etch, on hand, and read, on the other hand, digital watermarks in the stream that do not visibly interfere with the video content. A system according to the invention operates on digital data that has been transformed into the spatial-frequency domain, using inter-block differences between spatial-frequency coefficients to encode the bits of a digital watermark. Using the principles of the invention, it is possible to encode multiple watermark bits between two adjacent blocks, thus providing higher watermark data rates relative to underlying video content.

Claims

1. A method for etching a digital watermark comprising:

(a) providing a watermark bit;

(b) providing a digital media stream comprising a first block and a second block, the first block comprising a first plurality of coefficients, and the second block comprising a second plurality of coefficients, each one of the second plurality of coefficients corresponding to one of the first plurality of coefficients; and

(c) setting a first difference to a predetermined value according to the watermark bit, the first difference being a difference between a first coefficient of the first block and a corresponding first coefficient of the second block.

2. The method of claim 1 further comprising repeating (a)-(c) for a plurality of consecutive watermark bits and a plurality of consecutive blocks, wherein the second block is used as a new first block, and a third consecutive block is used as a new second block.

3. The method of claim 1 wherein setting the first difference to a predetermined value according to the watermark bit further comprises setting the first difference to a first level if the watermark bit is a one, and setting the first difference to a second level if the watermark bit is a zero.

4. The method of claim 3 wherein the first level is a binary even level and the second level is a binary odd level.

5. The method of claim 4, wherein setting the first difference to a binary even level further comprises adding a quantization level to the corresponding first coefficient if the first difference is odd, and wherein setting the first difference to a binary odd level further comprises adding a quantization level to the corresponding first coefficient if the first difference is even.

6. The method of claim 1 further comprising:

providing a second watermark bit; and

setting a second difference to a predetermined value according to the second watermark bit, the second difference being a difference between a second coefficient of the first block and a corresponding second coefficient of the second block.

7. The method of claim 2 wherein the plurality of consecutive watermark bits comprises an encrypted watermark.

8. The method of claim 1 wherein the digital media stream comprises a Motion Picture Expert Group video stream, the first coefficient being a DC coefficient.

9. The method of claim 1 wherein the digital media stream comprises a Motion Picture Expert Group video stream, the first coefficient being an AC coefficient.

10. A method for reading a digital watermark comprising:

(a) receiving a digital media stream comprising a first block and a second block, the first block comprising a first plurality of coefficients, and the second block comprising a second plurality of coefficients, each one of the second plurality of coefficients corresponding to one of the first plurality of coefficients;

(b) determining a first difference between a first coefficient of the first block and a corresponding first coefficient of the second block; and

(c) determining a watermark bit, the watermark bit having a predetermined value according to the first difference.

11. The method of claim 10 further comprising repeating (a)-(c) for a plurality of consecutive blocks, wherein the second block is used as a new first block, and a third consecutive block is used as a new second block, thereby determining a plurality of consecutive watermark bits.

12. The method of claim 10, the predetermined value being a one if the first difference has a first level, and the predetermined value being a zero if the first difference has a second level.

13. The method of claim 12 wherein the first level is a binary even level and the second level is a binary odd level.

14. The method of claim 10 further comprising:

determining a second difference between a second coefficient of the first block and a corresponding second coefficient of the second block; and

determining a second watermark bit, the second watermark bit having a second predetermined value according to the second difference.

15. The method of claim 11 wherein the plurality of consecutive watermark bits comprises an encrypted watermark.

16. The method of claim 10 wherein the digital media stream comprises a Motion Picture Expert Group video stream and the first coefficient is a DC coefficient.

17. The method of claim 10 wherein the digital media stream comprises a Motion Picture Expert Group video stream and the first coefficient is an AC coefficient.

18. A system for etching a digital watermark comprising:

means for providing a watermark bit;

means for providing a digital media stream comprising a first block and a second block, the first block comprising a first plurality of coefficients, and the second block comprising a second plurality of coefficients, each one of the second plurality of coefficients corresponding to one of the first plurality of coefficients;

means for either setting a first difference to a first level if the watermark bit is a one, or setting the first difference to a second level if the watermark bit is a zero, the first difference being a difference between a first coefficient of the first block and a corresponding first coefficient of the second block; and

means for providing a plurality of consecutive watermark bits and a plurality of consecutive blocks to the above means, wherein the second block is used as a new first block, and a third consecutive block is used as a new second block.

19. The system of claim 18 wherein the first level is a binary even level and the second level is a binary odd level.

20. The system of claim 18 further comprising:

means for providing a second watermark bit; and

means for either setting a second difference to be even if the watermark bit is a one, or setting the second difference to be odd if the watermark bit is a zero, the second difference being a difference between a second coefficient of the first block and a corresponding second coefficient of the second block.

21. The system of claim 18 further comprising means for encrypting the plurality of consecutive watermark bits into an encrypted watermark.

22. The system of claim 18 further comprising means for variable-length decoding the first plurality of coefficients and the second plurality of coefficients before applying the determining means and the setting means, and means for variable-length coding the first plurality of coefficients and the second plurality of coefficients after applying the determining means and the setting means.

23. A digital video encoder comprising:

a watermark source, the watermark source providing a plurality of watermark bits;

a transform unit, the transform unit receiving a plurality of blocks of video data and performing a two-dimensional transform on each block to provide a transformed block, each transformed block including a plurality of coefficients;

a quantizer, the quantizer receiving each transformed block and scaling each coefficient of each transformed block using a quantization index, thereby providing a plurality of quantized blocks; and

a watermark unit, the watermark unit receiving one of the plurality of watermark bits from the watermark source, a first one of the plurality of quantized blocks, and a second one of the plurality of quantized blocks, the watermark unit encoding the one of the plurality of watermark bits by setting a difference to be even if the one of the plurality of watermark bits has a first value and setting the difference to be odd if the one of the plurality of watermark bits has a second value, the difference being a difference between a first coefficient of the first one of the plurality of quantized blocks and a corresponding first coefficient of the second one of the plurality of quantized blocks.

24. The digital video encoder of claim 23 wherein the first coefficient and the corresponding first coefficient are DC coefficients.

25. The digital video encoder of claim 23 wherein the first coefficient and the corresponding first coefficient are AC coefficients.

26. The digital video encoder of claim 23 wherein setting the difference to be even comprises adding a quantization level to the corresponding first coefficient if the difference is odd, and wherein setting the difference to be odd comprises adding a quantization level to the corresponding first coefficient if the difference is even.

27. The digital video encoder of claim 24 wherein the plurality of quantized blocks comprises a Motion Picture Expert Group video stream.

28. A digital watermark embodied in a digital video stream carrier signal, the digital watermark comprising a plurality of watermark bits, each watermark bit having a value encoded between consecutive blocks of the digital video stream, the value being a first value when a difference between a pair of consecutive corresponding coefficients is even, and the value being a second value when the difference between the pair of consecutive corresponding coefficients is odd.

29. The digital watermark of claim 28, wherein the first value is one and the second value is zero.

30. The digital watermark of claim 28, wherein the first value is zero and the second value is one.

31. The digital watermark of claim 28 wherein the pair of consecutive corresponding coefficients are each DC coefficients.

32. The digital watermark of claim 28 wherein the pair of consecutive corresponding coefficients are each AC coefficients.

33. A computer program product for etching a digital watermark, embodied in machine executable code for performing the following steps:

(a) providing a watermark bit;

(b) providing a digital media stream comprising a first block and a second block, the first block comprising a first plurality of coefficients, and the second block comprising a second plurality of coefficients, each one of the second plurality of coefficients corresponding to one of the first plurality of coefficients; and

(c) setting a first difference to a predetermined value according to the watermark bit, the first difference being a difference between a first coefficient of the first block and a corresponding first coefficient of the second block.

34. The computer program product of claim 33, further comprising machine executable code for repeating (a)-(c) for a plurality of consecutive watermark bits and a plurality of consecutive blocks, wherein the second block is used as a new first block, and a third consecutive block is used as a new second block.

35. The computer program product of claim 33 wherein setting the first difference to a predetermined value according to the watermark bit further comprises setting the first difference to a first level if the watermark bit is a one, and setting the first difference to a second level if the watermark bit is a zero.

36. The computer program product of claim 35 wherein the first level is a binary even level and the second level is a binary odd level.

37. The computer program product of claim 36 wherein setting the first difference to a binary even level further comprises adding a quantization level to the corresponding first coefficient if the first difference is odd, and wherein setting the first difference to a binary odd level further comprises adding a quantization level to the corresponding first coefficient if the first difference is even.

38. The computer program product of claim 33 further comprising machine executable code for performing the following steps:

providing a second watermark bit; and

setting a second difference to a predetermined value according to the second watermark bit, the second difference being a difference between a second coefficient of the first block and a corresponding second coefficient of the second block.

39. The computer program product of claim 34 wherein the plurality of consecutive watermark bits comprises an encrypted watermark.

40. The computer program product of claim 33 wherein the digital media stream comprises a Motion Picture Expert Group video stream, the first coefficient being a DC coefficient.

41. The computer program product of claim 33 wherein the digital media stream comprises a Motion Picture Expert Group video stream, the first coefficient being an AC coefficient.