Exploiting interframe redundancies in the lossless compression of 3D medical images
Summary form only given. An evaluation is made of different approaches to removing interframe redundancies. The test images we used are the MRI and CT images available from the Visual Human Project. Firstly, we found that linear predictive techniques are not able to provide any compression improvement. Even an optimal linear predictor (least-squares optimization), which holds pixels from the current and the previous frames, does not outperform the very simple 2D lossless JPEG predictor number 7. However nonlinear techniques, such as context-modeling do yield better results. In a simple experiment, lossless JPEG was estimated to code intraframe prediction errors using an interframe context. The context for coding the current pixel is formed by the magnitude of the prediction error of the corresponding pixel in the previous frame. Note that this prediction error comes from the intraframe prediction step in the previous frame. Using this interframe context-modeling approach, a reduction of the bit rate of up to 1 bit per pixel is obtainable. It is obvious that the context serves as an edge-detector, albeit a very simple and straightforward one. A new technique is proposed based on the 2D lossless image compressor JPEG-LS. The existing context-modeling scheme is extended to also catch the interframe redundancies. The interframe context is very similar to the abovementioned one, however the sign of the prediction error in the previous frame is also used.