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.

The invention relates to an improved spread transform dither modulation (STDM) watermarking method and belongs to the technical field of digital watermarks. STDM watermarking has the combined advantages of quantization index modulation watermarking and a spread spectrum communication system, and high large watermark capacity and high robustness and has the disadvantage of high sensitivity to amplitude scaling attack. The invention constructs a signal invariable relative to the scaling for quantification by using a method which comprises: extracting from original content a statistical characteristic sequence which has a characteristic of scaling with original data according to the same scale factor; and obtaining the signal invariable relative to the amplitude scaling by dividing a carrier signal by the introduced characteristic sequence correspondingly. Watermark embedment and detection operation are both carried out on the newly constructed signal. The method improves the robustness of watermarks to amplitude scaling greatly and obtains watermarking performance similar to the original STDM watermarking in other aspects.

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.

The invention provides an iterative self-adapting quantitative index modulation watermarking method basing on a visual model, which includes the following steps: (1) to a specific value to be quantified, the quantization step is determined through a Watson visual model and varies with the varieties of the value to be quantified; (2) the quantization step is adopted, and a quantitative index modulation algorithm is used for embedding a watermark; (3) an iterative embedding process is added in the watermark embedding process, the watermark is detected after every bit is embedded. If the embedding is detected to be failed, the bit is embedded again. And if the embedding is detected to be successful, the embedding of a next bit is started. The iterative self-adapting quantitative index modulation watermarking method basing on a visual model determines the quantization step through the Watson visual model, eliminates the watermark extraction error of the watermark embedding detection caused by the inconsistency of the quantization step, which is provided with better robustness, can enhance the strength of the watermark under the condition of guaranteeing the invisibility of the watermark and guarantees the accurate detection of the watermark through the iterative embedding method. The watermark embedding process is shown as Figure 1.