Digital watermarking
AssigneeVerizon Laboratories Inc.
InventorsArianne M. Lewis, Evert Basch
Life of this patent
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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.
Claims41
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.
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.
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.
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.
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.
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.
Dependencies are inferred from the claim text.