Selective lossless retention of critical thermal data within highly compressed thermal video sequences

Abstract

The research described in this thesis involves the development of a video coding scheme which provides lossless Region Of Interest (ROl) coding specifically targeted toward the compression of thermal video sequences. In particular the scheme is designed to provide lossless coding of critical temperature data contained in thermal video sequences used within firefighting applications. High coding efficiency is achieved by the use of Discrete Cosine Transform (DCT) based lossy coding for non-critical areas of the video sequence.
The research is divided into three key sections; an investigation into thermal video, the practical development of a novel scheme for selective lossless compression of thermal video containing critical temperature data, and the presentation and analysis of test results which demonstrate the effectiveness of the scheme.
The scheme's multi-pass encoder stores data which enables the recovery of the losses which occur within critical thermal data as a result of the lossy DCT coding stage. This error recovery data is stored as codewords where each individual codeword is used to represent the error data for up to two pixels within the ROI. Efficient entropy coding of the error recovery data is achieved through a combination of a new adaptive reordering scheme followed by Run Length Coding (RLC) and Variable Length Coding (VLC).
By storing these error recovery codes within the normally unused colour channels of a compressed video sequence, the compressed thermal video sequence can be transmitted as an MPEG-1, MPEG-2 and MPEG4 compliant bitstream. This novel storage mechanism allows the error recovery codes to be spatially mapped to the ROl data, and hence the scheme can benefit from the motion compensation facilities provided within the MPEG compliant bitstream.
Decoding of the lossy video sequence can be carried out using any MPEG compliant decoder. Lossless ROl decoding can be carried out using the special decoder described in, and provided with, the thesis.