Distortion Accumulation in Image Transform Coding/Decoding Cascades

TitleDistortion Accumulation in Image Transform Coding/Decoding Cascades
Publication TypeTechnical Report
Year of Publication1991
AuthorsGilge, M.
Other Numbers694

With an increasing number of applications that employ transform coding algorithms for data reduction, the effect of distortion accumulation caused by multiple coding needs to be investigated. Multiple coding occurs when more than one coding system is connected in a cascade. From the second stage on, the coding algorithm operates on data that has been previously coded/decoded. First a generic image communication system is being modeled and situations that can lead to distortion accumulation are analyzed. These results show two main reasons for distortion accumulation, which are separately and jointly investigated using a JPEG-type compression algorithm. The first situation involves geometric operations between the decoding and next coding step. Measurements show however that these spatial manipulations are the main contributors to distortion accumulation. The second reason for distortion accumulation is a misalignment of the block segmentation reference point in subsequent transform operations. A block raster detection algorithm is derived that can find the position of the block raster that was introduced in a previous coding step. If this information is used in the block segmentation of the following coding step, distortion accumulation can be avoided. Simulation results are given for an extended algorithm that registers regions of homogeneous block raster in images consisting of several subimages.

Bibliographic Notes

ICSI Technical Report TR-91-064

Abbreviated Authors

M. Gilge

ICSI Publication Type

Technical Report