Fred Mintzer

An invisible watermarking technique for image verification

We propose a new method for invisibly watermarking high-quality color and gray-scale images. This method is intended for use in image verification applications, where one is interested in knowing whether the content of an image has been altered since some earlier time, perhaps because of the act of a malicious party. It consists of both a watermark stamping process which embeds a watermark in a source image, and a watermark extraction process which extracts a watermark from a stamped image. The extracted watermark can be used to determine whether the image has been altered. The processing used in the stamping and extraction processes is presented. We also discuss some advantages of this technique over other invisible watermarking techniques for the verification application; these include a high degree of invisibility, color preservation, ease of decoding, and a high degree of protection against retention of the watermark after unauthorized alterations.

Filters for distortion-free two-band multirate filter banks

In this paper, conditions are given for a two-band multi-rate filter bank to be alias free and to have a unity frequency response. It is shown that the class of quadrature mirror filters (QMFs) that satisfies these conditions is quite limited. A class of filters which does satisfy these conditions is given, and a simple procedure for designing filters from this class is presented with an example.

On half-band, third-band, and Nth-band FIR filters and their design

Half-band FIR digital filters are known to be important due to their reduced computational requirements. They are especially valuable when used to decimate or interpolate by a factor of 2 [1], where their characteristics well match the filtering requirements. Computational savings can also be achieved by extending the concept of half-band filters to Nth-band filters for use in decimation or interpolation by a factor of N. In this paper, it is shown that for certain filter requirements, common to decimation and interpolation, an Nth-band filter exists with passband and stopband ripples only slightly larger than those of the optimal FIR filter. It is demonstrated that optimal half-band filters can be designed by using the computer program of McClellan, Parks, and Rabiner [2]. It is also shown that useful Nth-band filters can be designed by using this program, which is perhaps the most widely available filter design program.

Effective and ineffective digital watermarks

We have entered an era where inexpensive and readily-available equipment can produce perfect copies of digital multimedia materials, such as CD-quality audio, publication-quality images, or digital video. In this environment, it has become easier for malicious parties to make salable copies of copyrighted content without compensation to the content owner. Many media content owners are concerned about the potential loss of revenue from multimedia piracy, especially when the content will be exposed to the Internet. Digital watermarking is seen by many as a potential solution to this problem. Many different watermarking schemes have been proposed. Often, however there is little discussion of how effective a proposed watermarking technique may be at solving a particular problem. We describe a number of proposed image-watermarking application scenarios and form a small number of watermark-application categories. Then, with these applications in mind, we discuss the desired technical properties of watermarks for each category. Finally we discuss some watermarking techniques developed by the authors, in light of the desired properties.

If one watermark is good, are more better?

Invisible watermarks are not all alike. Different techniques are used to embed different types of watermarks into digital media objects to accomplish different goals. Some watermarks are intended to robustly carry ownership information; some are intended to carry content-verification information; and some are intended to convey side information, or captions. Some opportunities to employ multiple watermarks to convey multiple sets of information, intended to satisfy differing or similar goals, are examined. Problems presented by the insertion of multiple watermarks are discussed. Progress towards developing techniques that embed multiple watermarks into an image are also presented.

Digital access to antiquities

toward worldwide access to digital images of art, ancient artifacts, historic manuscripts, and other materials of worldwide significance. Since 1985, we have worked with collections of artistic and historic materials, including the included here suggest the cultural values motivating this work, portions of which can now be conveyed quickly to scholars and students desktops. We pay special attention to quality representation and intellectual property rights. Collection curators have varying usage policies, from restrictive to permissive, but all want their holdings to be tastefully represented. Internet-delivered replicas of manuscript pages are good enough for much research but usually not for commercial piracy. And digital watermarks now provide an As a direct path to original sources, digitized manuscripts and images should reflect not only the artists values but the readers privacy and the owners confidentiality.

The design of optimal multirate bandpass and bandstop filters

Narrow-band bandpass and bandstop filters are inherently of high order and require a large computation rate. A multirate filter using decimators and interpolators can be designed to have bandpass or bandstop characteristics, often with a much smaller computation rate. This paper develops rules for designing such a filter by placing constraints on the filter approximation error and the aliasing error. The question of admissible decimation factors is investigated in detail. A method to minimize the computation rate is described. Several examples are presented.

Populating the Hermitage Museum's new web site

Experts from around the world tackle one of the most ambitious Web-based museum projects and the result captures the true artistry of teamwork, technology, and yes, art.

Digital implementation of frequency division multiplexing on peak-limited channels

The authors present a coding/modulation scheme with design criteria to deal with the peak power constraint on Fourier transform division multiplexing (FTDM). They clip the transmitted signal at some prescribed limit to preserve linearity and base the design on an estimate of the statistics of the errors due to clipping. They have tested these schemes on simulated data with good results. The authors comment on the performance of these schemes and how it relates to the shape of the channel response.<<ETX>>

A microprocessor for signal processing, the RSP

Signal processing is a data processing domain that contains a diversity of applications, including speech processing, image processing, radar, sonar, medical imaging, data communications, seismic processing, and many others. Despite the diversity of the applications, this processing domain has a very structured set of characteristics. These include real-time operation, dominance of arithmetic operations, and well-structured data flows. The Real-Time Signal Processor (RSP) is a microprocessor architecture that was created to exploit these characteristics in order to provide an expeditious and economical way to implement signal processing applications. In this paper, the organization and architecture of the RSP are described. Features of the RSP, such as the instruction pipeline and the fractional fixed-point arithmetic, which exploit the characteristics of signal processing to provide additional computational power, are emphasized. Other features, such as the powerful indexing, the saturation arithmetic, the guard bits, and the double-word-width accumulator, which add much to the processors versatility and programmability, are also highlighted. The performance of the RSP is illustrated through examples.