ADVANCED PAL DECODING: Exploration of some adaptive techniques

The need for improved decoding of conventional PAL in the broadcast chain is first established, in the context of future developments. The work done on this subject in the last twenty years is then reviewed, concluding that currently available decoders, while generally demonstrating a high level of performance, are nevertheless still capable of further improvement. Software simulations of two methods of PAL decoding are then described, using adaptive multi-field filters. The first, simple method adapts between filters based on picture, line and element delays; whereas the second, more complex method adapts between all possible combinations of three picture points within a vertical-temporal neighbourhood limited by four fields and four lines. The conclusion is reached that the simpler method is superior although the more complex method was not investigated so thoroughly. The simpler method also gives a result that is slightly superior to that currently available. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior permission.