Digital watermarking of low bit rate video

• US 20040125952A1
• Filed: 08/06/2003
• Published: 07/01/2004
• Est. Priority Date: 01/22/2002
• Status: Active Grant

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Lin, Eugene T., Alattar, Adnan M., Celik, Mehmet
• Granted Patent: US 7,567,721 B2
• Time in Patent Office: Days
• US Class Current: 380/202
• CPC Class Codes: G06T 1/0064 Geometric transfor invariant watermarking, e.g. affine transform invariant
• CPC Class Codes: G06T 1/0071 using multiple or alternating watermarks
• CPC Class Codes: G06T 1/0085 Time domain based watermarking, e.g. watermarks spread over several images
• 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 2201/0061 Embedding of the watermark in each block of the image, e.g. segmented watermarking
• CPC Class Codes: G06T 2201/0065 Extraction of an embedded watermark; Reliable detection
• CPC Class Codes: G06T 2201/0601 whereby calibration information is embedded in the watermark, e.g. a grid, a scale, a list of transformations

Abstract

Methods for embedding digital watermarks in compressed video include perceptual adapting a digital watermark in predicted and non-predicted data based on block activity derived from the compressed video stream, embedding in predicted objects in a video stream having separately compressed video objects, and bit rate control of watermarked video.

Claims

1. A method for embedding a digital watermark in a compressed video stream comprising:

receiving a compressed video stream;

extracting transform domain coefficients from the compressed video stream;

computing an adaptive watermark signal strength based on an activity estimate of the transform domain coefficients; and

embedding the adapted watermark signal into the transform domain coefficients.

2. The method of claim 1 wherein computing the activity estimate includes computing activity for a block of transform coefficients and weighting the watermark signal strength for the block based on the activity for the block relative to the activity of other blocks in the video stream.

3. The method of claim 2 wherein the video stream includes one or more separately compressed video objects, and the watermark strength for a block in a video object is weighted based on the activity of the block relative to the activity of other blocks in the same video object.

4. The method of claim 1 wherein the activity estimate is derived from energy of transform coefficients extracted from the compressed video stream.

5. The method of claim 1 wherein the adaptive watermark signal is computed for non predicted and predicted video data.

6. The method of claim 5 wherein the watermark signal strength derived from non-predicted video data is used along with motion information that describes motion between the predicted and non-predicted video data to compute watermark signal strength for predicted video data.

7. The method of claim 6 wherein the motion information is extracted from motion vectors in the compressed video stream.

8. A tangible medium on which is stored instructions for performing the method of claim 1.

9. A method for embedding a digital watermark in a compressed video stream comprising:

receiving a compressed video stream;

extracting transform domain coefficients from the compressed video stream;

computing an adaptive watermark signal strength based on quantization indexes of the transform domain coefficients; and

embedding the adapted watermark signal into the transform domain coefficients.

10. A tangible medium on which is stored instructions for performing the method of claim 9.

11. A method for embedding a digital watermark in a compressed video stream, the compressed video stream including two or more separately compressed video objects, the method comprising:

receiving a video stream with separately compressed video objects that are combined to form a video, wherein at least one of the video objects is compressed using a non predicted object and predicted objects based on the non-predicted object and motion data describing motion between the non predicted and predicted object;

embedding a digital watermark into the non predicted object; and

embedding a digital watermark into the predicted objects, including compensating for the digital watermark previously embedded in a video object from which the predicted objects are predicted.

12. The method of claim 11 wherein the non predicted object comprises a sprite and embedding the digital watermark into the predicted objects includes inserting the digital watermark in sprite update mode.

13. A tangible medium on which is stored instructions for performing the method of claim 11.

14. A method for embedding a digital watermark in a compressed video stream having base and enhancement layers enabling temporal or spatial scalability of the video stream, the method comprising:

embedding a digital watermark in a base layer at a first resolution;

embedding the digital watermark in an enhancement layer of the base layer;

wherein the digital watermark is detectable from video comprising only the base layer at the first resolution, and from video comprising a combination of the base and enhancement layer to form a second resolution.

15. The method of claim 14 wherein embedding a digital watermark in one layer is compensated for in embedding a digital watermark in a second layer so that the digital watermarks in the layers do not interfere with each other.

16. The method of claim 14 wherein the base layer is at a first temporal resolution, and the enhancement layer is used to form video at a second temporal resolution.

17. The method of claim 14 wherein the base layer is at a first spatial resolution, and the enhancement layer is used to form video at a second spatial resolution.

18. The method of claim 17 wherein one of the layers is used to predict the other layer in compression of the video, and embedding a digital watermark in one layer is compensated for in embedding a digital watermark in a second layer so that the digital watermarks in the layers do not interfere with each other due to the use of prediction coding.

19. A tangible medium on which is stored instructions for performing the method of claim 14.

20. A method for embedding a digital watermark in a compressed video stream, the method comprising:

providing watermark signals for first and second blocks of transform coefficients in the compressed video stream, wherein coefficients in the second block are predicted from coefficients in the first block; and

for predicted coefficients in the second block, adjusting for the watermark signal from the first block when inserting the watermark signal for the second block such that the watermark signals for the first and second blocks due not interfere due to the prediction.

21. The method of claim 20 wherein adjusting comprises:

subtracting the watermark signal of the first block for the coefficients in the second block that are predicted from the coefficients of the first block to produce a prediction compensated watermark signal; and

adding the prediction compensated watermark signal to the second block.

22. A tangible medium on which is stored instructions for performing the method of claim 20.

23. A method for embedding a digital watermark in a compressed data stream using bit control to control modifications to bit rate of the compressed data stream due to the embedding of the digital watermark, the method comprising:

embedding a digital watermark into the compressed data stream to form a watermarked compressed data stream;

for blocks of quantized transform coefficients of the watermarked compressed data stream, controlling bit rate of the data stream by selectively eliminating non-zero quantized transform coefficients with smallest magnitude in the block according to a bit allocation method that assigns a bit budget per block.

24. The method of claim 23 wherein the bit allocation method allocates bits to blocks of coefficients depending on texture of the image represented by the block, wherein blocks with more texture than other blocks are allocated more bits than other blocks.

25. The method of claim 23 wherein the bit allocation method allocates bits to blocks of coefficients depending on a local watermark strength computed for the blocks, wherein blocks with higher watermark strength are allocated more bits than other blocks.

26. A tangible medium on which is stored instructions for performing the method of claim 23.

27. A method for embedding a digital watermark in a compressed video stream comprising:

receiving a compressed video stream;

extracting prediction information from the compressed video stream, the prediction information including motion vectors;

computing an adaptive watermark signal strength based on the prediction information; and

embedding the adapted watermark signal into the compressed video stream.

28. The method of claim 27 wherein the adapted watermark is embedded in transform domain coefficients extracted from the compressed video stream.

29. The method of claim 28 including:

computing the adaptive watermark signal strength based on quantization indexes of the transform domain coefficients and the prediction information.

30. The method of claim 28 including:

computing an adaptive watermark signal strength based on an activity estimate of the transform domain coefficients and the prediction information.

31. The method of claim 28 including:

computing an adaptive watermark signal strength based on an activity estimate of the transform domain coefficients, based on the quantization indexes and based on the prediction information.

32. The method of claim 27 wherein the prediction information includes spatial prediction information from the compressed video stream.

33. The method of claim 27 wherein the prediction information includes temporal prediction information from the compressed video stream.

34. The method of claim 27 wherein the prediction information includes temporal and spatial prediction information from the compressed video stream.

35. A tangible medium on which is stored instructions for performing the method of claim 27.