Apparatus for hierarchical encoding of digital image signals with improved encoding efficiency

A method of encoding an input digital video signal to produce at least first and second hierarchical data signals which respectively represent a first video signal and a second video signal having a resolution that is lower than a resolution of the first video signal, the method comprising the steps of:

• receiving the input digital video signal;
• generating the second hierarchical data signal by calculating each pixel data signal of the second hierarchical data signal as a weighted average of a number (N) of pixel data signals of the received input digital video signal;
• and
• outputting the generated second hierarchical data signal together with first hierarchical pixel data signals representing only N−1 of the N pixel data signals of the input digital video signal.

An apparatus for forming at least first, second and third encoded hierarchical data signals, said apparatus comprising:

• means for receiving an input digital video signal representing data of a plurality of groups of pixels in which each group has a number (N) of said pixels and for encoding the data of N−1 pixels of each of said groups so as to form the first encoded hierarchical signal;
• means receiving said input digital video signal for weight averaging the data representing the N pixels of each of said groups of pixels so as to form at least one group of weight averaged data in which each weight averaged data group has a number (M) of weighted average data values;
• means for encoding M−1 weighted average data values of each said weight averaged data group so as to form the encoded second hierarchical signal;
• and
• means for weight averaging the data values of each said weight averaged data group and for forming the encoded third hierarchical data signal therefrom.