Dynamisches Differenz-Keying in Chroma-Keying-Umgebungen
Ulrich Dr.-Ing. Schmedes · 2014
In a virtual television studio and in chroma keying environments in general, people interact in front of a monochrome background in order to allow a replacement of that background by a computer-generated virtual background in the following signal processing. Uniformity of the setting is required in order to distinguish objects in a studio from the background in a segmentation process based on colour information. However, this uniformity is a problem concerning orientation for the person interacting in the studio as visual feedback regarding the virtual things that are happening, as well as the final composition of the image, is missing.Within this thesis a new method that allows the projection of the virtual background on to the studio wall in full colour intensity is introduced. For this purpose the projected image is taken as a basis. All changes the picture is subjected to on its way from the projector to the camera are replicated in a multilevel algorithm via computer. Both camera perspective as well as field of view and changes in brightness and colour and also influences of the real studio environment are included. The algorithm provides a comparison image which corresponds to the image of the camera in an empty studio. A subsequent comparison with the image taken by the camera during the actual filming assigns all matching pixels in both pictures to the background of it, whereas varying pixels are allocated with the foreground obscuring the background at this place. Because of its fundamental similarity to Difference Keying – which, however, is extended by the possibility of resorting to a changeable background image as well as potentially changeable field of view – it is proposed that the method be called Dynamic Difference Keying.A proof of concept demonstrates the practicality of the method and depicts possible future aspects of further developments.