AbstractMajor activity and interest has focused upon High and Enhanced Definition Television systems, for at least the past few decades. From the initial analogue approaches, which concentrated on purely television enhancements, the focus continues to fade more towards fully digital multi-program distribution and ultimately to multimedia solutions. The actual activities throughout Europe and America in launching the Digital Video Broadcasting, DVB and the Advanced Television System Committee, ATSC system, clearly identify that television enhancements are still alive. In parallel, discussions upon data broadcasting, predominantly within the current analogue television systems also have taken place.
The underlying premise of the work presented, is based upon the objective to transmit a compatible enhanced definition television signal within the PALplus standard. A conceptual system is proposed as the framework for this research, containing both a pre-processing and data modulation block, which are coupled via suitable data compression methods. The preprocessing and the additional digital modulation technique has been identified as providing the potential of innovation from which the modulation provides generic digital sub-channels either for multimedia or enhanced resolution extensions.
The originality of the pre-processing techniques is based upon the design of a dual channel sub-band system, which employs two dimensional diagonal filtering together with a Quadrature Mirror Filter bank. From a high definition input, this processing block produces only two sub-bands, rather than the usual four, from which the low pass element represents the compatible component. The high pass element conveys the residual in such a way that full horizontal and vertical resolution can be reconstructed during decoding. The proposed embedded data modulation strategy is based upon a double occupation of the colour subcarrier. This exploitation is possible due to the inherent phase alternation of the PAL systems so that an additional quadrature modulation of the two colour sub-carriers is feasible.
Both, the pre-processing and modulation blocks introduce crosstalk distortions which compromise the overall efficiency and further encroach on the sensitive issue of compatibility. The thesis provides a complete analysis both theoretical and practical of the implications of these distortions and subsequently proposes solutions which either eliminate or suppress them to a level below a perceptual threshold.
|Date of Award||Mar 1999|
- High Definition Television
- Enhanced Definition Television
- television signal