Method and apparatus for watermarking video images

• US 6,798,894 B2
• Filed: 02/06/2001
• Issued: 09/28/2004
• Est. Priority Date: 05/16/1996
• Status: Expired due to Term

• Current Assignee: Digimarc Corporation
• Original Assignee: Digimarc Corporation
• Inventors: Rhoads, Geoffrey B.
• Primary Examiner(s): Couso, Jose L.
• Application Number:
  US09/778,307
• Publication Number:
  US 20010017931A1
• Time in Patent Office: 1,330 Days
• Field of Search: 382/100, 358/3.28, 380/201, 380/202, 380/203, 380/210, 380/216, 380/231, 380/287, 348/460, 348/461, 348/473, 348/474, 370/527, 370/528, 370/529, 381/73.1, 704/200.1, 704/270, 704/273
• US Class Current: 382/100
• CPC Class Codes: G06T 1/0035 Output size adaptive watermarking
• CPC Class Codes: G06T 1/0064 Geometric transfor invariant watermarking, e.g. affine transform invariant
• 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: G06V 30/40 Document-oriented image-based pattern recognition
• CPC Class Codes: G10L 19/018 Audio watermarking, i.e. embedding inaudible data in the audio signal
• CPC Class Codes: G11B 20/00884 involving a watermark, i.e. a barely perceptible transformation of the original data which can nevertheless be recognised by an algorithm
• CPC Class Codes: G11B 2020/10537 Audio or video recording
• CPC Class Codes: H04N 1/00005 relating to image data
• CPC Class Codes: H04N 1/00037 Detecting, i.e. determining the occurrence of a predetermined state H04N1/00031 takes precedence
• CPC Class Codes: H04N 1/00079 remotely
• CPC Class Codes: H04N 1/32122 in a separate device, e.g. in a memory or on a display separate from image data
• 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 1/32187 with selective or adaptive application of the additional information, e.g. in selected frequency coefficients
• CPC Class Codes: H04N 1/32277 Compression
• CPC Class Codes: H04N 1/32352 Controlling detectability or arrangements to facilitate detection or retrieval of the embedded information, e.g. using markers for decoding, detection or retrieval operations H04N1/32149 and subgroups take precedence
• 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 19/60 : using transform coding
• CPC Class Codes: H04N 19/61 : in combination with predictive coding
• CPC Class Codes: H04N 2005/91335 : the copy protection signal being a watermark
• CPC Class Codes: H04N 21/23892 : involving embedding information at multiplex stream level, e.g. embedding a watermark at packet level
• 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
• CPC Class Codes: H04N 2201/3205 : of identification information, e.g. name or ID code H04N2201/3209 takes precedence
• CPC Class Codes: H04N 2201/3207 : of an address
• CPC Class Codes: H04N 2201/3233 : of authentication information, e.g. digital signature, watermark
• CPC Class Codes: H04N 2201/327 : which are undetectable to the naked eye, e.g. embedded codes
• CPC Class Codes: H04N 5/913 : for scrambling ; for copy protection

Abstract

Embedding a watermark in an image by changing selected DCT coefficients in the blocks and macro blocks of coefficients which represent the image. The changes in the blocks that comprise each macro block are done in a coordinated manner so that the phase of the watermark signal is preserved across the block boundaries. By preserving the phase across block boundaries, a detectable grid is formed which can be used as an orientation and scaling grid. Furthermore, by preserving the phase across block boundaries the visual artifacts introduced by the watermark are minimized. The bit rate of the image signal is preserved by maintaining a count (referred to as the cumulative change count) that represents the amount that the bit rate has been increased by changes in coefficients less the amount that the bit rate has been decreased by changes in the coefficients. If at any time the cumulative change count exceeds a pre-established limit, coefficient changes that decrease the cumulative change count continue; however, coefficient changes that increase the cumulative change count are suspended. The suspension of coefficient changes that increase the cumulative change count continues until the cumulative change count falls below the pre-established limit.

Claims

1. A method of introducing a watermark into a stream of bits comprising variable length codes that represent transform domain samples while insuring that a bit rate of said stream of bits is maintained within a pre-established limit, said method comprising, providing a watermark signal comprising changes to associated transform domine samples to embed the watermark signal in the samples, maintaining a cumulative change amount which indicates an amount of the positive and negative changes which are made to said codes as a result of embedding the watermark signal, adjusting the watermark signal changes to particular transform samples such that the amount of the adjustment and the change to the particular transform samples is non-zero yet the cumulative change amount is maintained below the pre-established limit, and suspending positive changes if the cumulative change amount exceeds the pre-established limit, whereby the bit rate of said stream of bits is maintained within the pre-established limit.

3. The method of claim 1 wherein negative changes are suspended if the cumulative change amount exceeds a pre-established negative amount.

2. A method of introducing a watermark into a stream of bits comprising variable length codes that represent transform domain samples while insuring that a bit rate of said stream of bits is maintained within a pre-established limit, said system comprising, means for providing a watermark signal comprising changes to associated transform domine samples to embed the watermark signal in the samples, means for maintaining a count of and amount of positive and negative changes which are made to said codes as a result of embedding the watermark signal, mean for adjusting the watermark signal changes to particular transform samples such that the amount of the adjustment and the change to the particular transform samples is non-zero yet the cumulative change amount is maintained below the pre-established limit, and means for suspending positive changes if a pre-established limit is exceeds, whereby the bit rate of said stream of bits is maintained within the pre-established limit.

4. The system of claim 2 including means for suspending any negative changes if said count exceeds a pre-established negative limit.

5. A method of embedding a watermark in a stream of coded symbols that represent a series of images by selectively increasing or decreasing values of said symbols according to associated values of the watermark, said method comprising, establishing a limit on allowable entropy of said stream of bits, adjusting an amount of the selective increasing or decreasing of the values of said symbols as entropy of the watermarked stream approaches the limit such that the watermark and the adjustment to the watermark is non-zero at selected symbols where the watermark is adjusted to maintain the entropy of the watermarked stream below the limit.

6. A method of embedding a watermark in a series of bit which represent an image without increasing entropy of said image beyond a pre established limit, comprising the steps of:

changing selective bits of said image to embed said watermark, maintaining a cumulative change count of the changes made to embed said watermark in said image, adjusting intensity of the watermark for at least a set of the selective bits to maintain the cumulative change count below the limit, where the adjustment and the intensity of the watermark is non-zero at the set of bits.

7. A method of embedding a watermark in a series of bit which represent an image without increasing entropy of said image beyond a pre established limit comprising the steps of:

maintaining a count which represents a change in entropy as said watermark is being embedded in said image, adjusting intensity of the watermark for at least a set bits to maintain the count below the limit, where the adjustment and the intensity of the watermark is non-zero at the set of bits, suspending changes in said image when said count is beyond a specified limit.