This work investigates the interface between a video sensor and a low bandwidth radio transmitter. In the context of a low-cost low-power radio video link, it outlines a hardware minimal solution. To solve the bandwidth conflict between the low power radio links and even a modest image sequence quality, a broad range of digital coding techniques are evaluated. Aspects of the coding methods other than the compression ratios they offer and the ability to implement them using minimal hardware are considered (in particular how vulnerable they leave the coded data to corruption through transmission errors). Through software simulation, implementations of the two most promising compression techniques: color quantisation with error-diffusion and localised differential predictive coding (DPCM) are further investigated. Particular emphasis is placed on implementation of the software algorithms using architectures close to those of the simplest hardware implementations. Implementation of the localised DPCM scheme is dropped on the grounds that its lossless implementation cannot offer sufficient compression, and that a lossy implementation would be too expensive in terms of the required memory. Colour quantisation with error diffusion is further pursued in the hardware implementation of two algorithms in the form of a field-programmable gate-array (FPGA). Results from the FPGA offer subjective analysis of the algorithms output at higher frame rate and the successful implementation of the architecture demonstrates the suitability to hardware implementation. A framework that was developed to allow comprehensive subjectivity testing of image processing algorithms is described and results, although statistically insignificant, are given. In evaluating the importance of the colour quantisation with error diffusion amongst other compression and coding techniques, this work concludes that where hardware is at a premium and strict viewing requirements can be met, there are applications where it can be applied profitably, offering results comparable with much more complicated solutions.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:659799 |
| Date | January 1997 |
| Creators | Murray, Andrew A. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/15466 |
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