35 results about "Quantization index modulation" patented technology

The invention addresses the problem of scale degradations that may occur in watermarking schemes based on quantization index modulation (QIM). In accordance with the invention, the quantization step size (D) being employed by the embedder (11) and detector (21) is derived (12, 22) from a measurable characteristic parameter which has the property that, when the applied signal is scaled by a factor (a), it is scaled by substantially the same factor. In a preferred embodiment, said parameter is the square root of the energy of the signal (), and the quantization step is a predetermined fraction (a) thereof.

It is possible to achieve very high data rates with quantization index modulation QIM, and the capacity of watermark transmission is largely independent of the characteristics of the original audio signal, but the audio quality degrades at each watermark embedding and removal step. To avoid degrading the audio quality, the audio signal watermarking of the present invention uses a specific quantizer curve in the time domain, especially in the frequency domain, to embed the watermark message into the audio signal, making the process almost completely reversible. Furthermore, it has embedded power constraints in order to guarantee that the modification to the signal caused by watermark embedding is inaudible.

An anti-collusion multimedia fingerprint method based on quantization index modulation in the field of digital information processing technology comprising the following steps: generating a fingerprint-containing copy by allocating a user IDs at a transmitting end, and performing collusion detection after obtaining a copy to be detected at a receiving end; and judging a conspirator through non-blind detection when the receiving end has original carrier information, otherwise judging the conspirator through blind detection. The anti-collusion multimedia fingerprint method uses two detection means of the non-blind detection and the blind detection, so that the conspirator can be correctly detected with very high probability, and capability of resisting collusion attack is very great.

There is provided a method of detecting a watermark included in a signal by way of quantization index modulation (QIM). The signal with the embedded watermark may have been geometrically transformed (e.g. spatially or temporally scaled) prior to detection. In order to detect the watermark even in such case, the embedder imposes an autocorrelation structure onto the embedded watermark data, for example by tiling. Initially, the detector applies conventional QIM detection. This step yields a first symbol vector, which corresponds to the embedded data when the signal was not tampered with, but does not correspond to the embedded data when the signal was subject to scaling. For example, when one data bit is embedded in each pixel of an image, 50% upsampling of the image causes a QIM detector to retrieve 3 data bits out of 3 received pixels, that is 3 data bits out of 2 original image pixels. Surprisingly, the autocorrelation of the first symbol vector will give a peak for a particular geometric transformation (e.g. the particular scaling factor). In accordance with the invention, the detector calculates said autocorrelation iunction, and uses the result to apply the inverse of the transformation, i.e. undo the scaling. A second pass of the conventional QIM detection will subsequently receive the embedded data.