Copro was founded in 1997 as a so called demo-group. To quote demoscene.info:
Demos are computer generated music clips that show what kind of graphic and sound effects can really be done by using high-end computer hardware to its full potential.
This activity got lost somewhere 2001. Malte Clasen restructured his personal website in 2006 to inform you about his research activities. Jan Clasen almost disappeared from the net, the Plastikball site being one of the few remains. Sven Wittig runs the Razer community website par excellence.
A few files are still available for download, although none of these is actively maintained:
Tensor is a modular software synthesizer. It is based on a normalized model of audio operators: You have several inputs, but only one output (either mono or stereo). This allows a quick construction of an audio processing tree, since you don't have to work with wires. Just stack the modules over each other and they get connected automatically.
Tensor is still in an early stage of development, and there's no planned release date. The project is currently on halt, and it's unlikely that it will be continued. If you're curious, brave and in posession of a recent C++ compiler, you might want to check out the development snapshot below. It features MIDI input, audio output and OpenGL output. Basic audio processing modules (vco, vca, vcf), some MIDI input handler and a sample OpenGL renderer are included, so you can build, load and save simple synthesizers with it.
In_Bass is a module player plugin for WinAMP 2.x/5.x which uses the BASS library for far better sound quality and exact replay of IT and especially XM modules. What you might miss is a smooth time bar and the possibility to read song texts for songs other than the one that's actually played, but if you don't need that, you should use this plugin instead of the default in_mod. The current release of the binaries is 1.8.0, kindly provided by Hans "Kvasi" Molin. Note that the sources (VC++ 6.0) are slightly outdated by now.
This realtime fluid simulator is based on Jos Stam's paper "stable fluids". It allows interactive control of fluids (including gases). A simple editor is included, although the main aspect lies on the implementation of the solver. Since it is released under the BSD license, you are free to use it in your own projects.
The implementation was developed by Malte Clasen, Tobias Rick and Steffen Conrad at the RWTH Aachen. It is written in C++ using Qt and OpenGL. The solver core is independent of third party libraries and should compile on all platforms that support C++. Visit the Source Forge project page for updates (which should be very rare these days).
Arithmetic coding is a quite common lossless compression scheme. It is similar to Huffman coding, but results in better compression while being a little bit slower. This introduction has been written by Malte Clasen, Eric Bodden and Joachim Kneis at the RWTH Aachen.
After a brief introduction, the basic terms on Arithmetic Coding (AC) are described. These are necessary for later chapters, in which we explain the algorithms of encoding and decoding in different numerical systems, pointing out problems which arise with these algorithms, for which solutions will be presented in subsequent sections. Following, we will derive estimations for the efficiency of AC and lead a proof for the unambiguity of the produced codes. In the end, we will briefly describe popular statistical models which are frequently used to gain compression using arithmetic coders. Occasionally, comparisons to Huffman Coding will be drawn, but only presuming a basic knowledge on this topic.
This work is essentially based on works by Sayood and Bell. Pertaining to the latter, we introduce a comprehensive implementation. The appendix gives the full source code for this. Some of the examples given are refering to this implementation. Mathematical definitions and proofs are rather based on Sayood and Fano. In addition, we presuppose the famous Shannon theorem , which proves the entropy to be the natural limit of lossless compression. The example source codes are developed in for C++. They were designed to be easy to read and understand. So they only incorporate basic C++ syntax.
Eric Bodden's website contains some additional material.