CECIL_B is a new Windows utility for automatic conversion of large sets of BMP files to high-quality, compact AVI movies. The program is of particular interest to researchers and engineers working with computer simulations. The design philosophy was to create a program to do one task and to do it well. As a result, it takes only a few minutes to install and to learn the program. Setting up a conversion takes only a few seconds, even with thousand of input graphics files. On startup, the program automatically detects codecs available on the user's computer. The instruction manual contains a no-nonsense discussion of codecs.