 Watermarking of a digitized image |
| OF THE INVENTION FIG. 1 illustrates the flow chart of the method for watermarking of digitized ... |
|
| Watermarking method and apparatus for compressed digital video |
| The present invention provides a method and apparatus for watermarking a compressed digital video ... |
|
| Method for embedding and reading watermark-information in digital form, and apparatus thereof |
| It is the object of the present invention to make it possible to read embedded information even if ... |
|
| Methods and systems for performing short integer chen IDCT algorithm with fused multiply/add |
| Methods for performing a two-dimensional inverse discrete cosine transform consistent with this ... |
|
| Method and apparatus for selecting image data to skip when encoding digital video |
| A block and frame skipping technique decides which image regions, blocks or frames in a video frame ... |
|
| Loudspeaker having a two-part diaphragm for use as a car loudspeaker |
| In order to obtain a frequency response characteristic with a broadened dip, the loudspeaker in ... |
|
| Horizontal synchronizing system |
| In accordance with an embodiment of the present invention, a phase control circuit for the ... |
|
| Multiple scanning type television receiver |
| The above problem is overcome by the present invention which is intended for use in combination ... |
|
| Selective efficiency videofrequency non-linearity correction device |
| The invention provides a selective efficiency video frequency nonlinearity correction device, for ... |
|
|
Methods for optimizing watermark detection
| Details |
Inventors: Rhoads, Geoffrey B.;
Assignee: Digimarc Corporation (Tualatin, OR)
Primary Examiner: Johns; Andrew W.
Assistant Examiner:
Attorney, Agent or Firm: Conwell; William Y.
Watermark detection in an image or the like is optimized by exploiting the innate biases in the image to emphasize the watermark signal. The watermark signal can be trial-located with different origins in the image to find one that yields improved results. Similarly, the image can be processed (e.g., by changing resolution, rotation, or compression) so as to change the innate biases to better reinforce the watermark signal. Compression of an image can be done in accordance with a desired watermark signal, with the compressor deciding which image components to retain and which to discard based, in part, on a watermark signal that is to be encoded (or maintained) in the image. |
|
DETAILED DESCRIPTION To mitigate the problem of detecting a watermark signal in the presence of a much-stronger image signal, certain choices are made early in the process--at the embedding operation.
The "noise" introduced by the image signal doesn't always hurt the detection process.
Sometimes innate biases in pixel values, or other image characteristics (e.
g.
, DCT, wavelet, or other transform coefficients), can actually serve to accentuate the watermark signal and thereby simplify detection.
Starting with a perhaps overly simple case, consider an image prior to watermark encoding.
If the un-encoded image is analyzed for the presence of a watermark, none should be found.
However, there are cases in which the innate image characteristics sufficiently mimic a watermark signal that a phantom watermark payload may nonetheless be decoded.
If the application permits, the user may then encode the image with this watermark payload.
This encoding just accentuates the phantom data signal coincidentally present in the image.
Even if all of the added watermark energy is somehow thereafter lost, the watermark may still be detectable.
Most watermark decoding algorithms are designed to guard against detection of phantom watermarks in un-encoded images.
For example, the algorithms may look for checksum bits in the watermark payload; if the payload bits don't correspond as expected to the checksum, the decoder may simply report that no watermark is detected.
Other algorithms may employ some confidence metric for each of the decoded bits (e.
g.
, signal-to-noise ratio).
Unless the confidence metric for all the decoded bits exceeds a threshold value, the decoder may again report that no watermark is detected.
In applying the principles detailed in this specification, it is generally desirable to disable or circumvent mechanisms that guard against detection of phantom data so as to essentially force the decoder to make its best guess of what the watermark payload is--assuming there is a watermark present.
In the case just discussed, this would involve circumventing checksum checks, and lowering the detection confidence thresholds until watermark data is discerned from the un-encoded image
|
|
Image Analysis 
