Methods and apparatus for wavelet-based image compression

An apparatus for implementing a multi-stage wavelet transform of an image signal, the apparatus comprising:

• a first stage processing element for implementing a first stage of the wavelet transform;
• and
• a multi-stage processing element for implementing at least two subsequent stages of the multi-stage wavelet transform in a time-multiplexed manner, using outputs generated by the first stage processing element;
• wherein the first stage processing element comprises a horizontal and vertical filter which operates on pixels of the image signal at a sampling rate fs;
• wherein the first stage processing element further comprises:
• a first adder tree for implementing horizontal filter operations;
• a set of row buffers configured to receive low pass and high pass outputs of the first adder tree;
• a set of multiplexers, with a given one of the multiplexers coupled between the outputs of the adder tree and an input of a corresponding one of the row buffers, and operative to select application of a low pass output or a high pass output of the first adder tree to the corresponding row buffer;
• and
• a second adder tree for implementing vertical filter operations, the second adder tree receiving its inputs from the set of row buffers, and generating vertically-filtered outputs one row at a time.

An apparatus for implementing a multi-stage wavelet transform of an image signal, the apparatus comprising:

• a first stage processing element for implementing a first stage of the wavelet transform;
• and
• a multi-stage processing element for implementing at least two subsequent stages of the multi-stage wavelet transform in a time-multiplexed manner, using outputs generated by the first stage processing element;
• wherein each of the first stage processing element and the multi-stage processing element comprises:
• a set of row history memory elements;
• a first adder tree for performing x-transform operations;
• a set of column history memory elements;
• and
• a second adder tree for performing y-transform operations.

A method of implementing a multi-stage wavelet transform of an image signal, the method comprising the steps of:

• implementing a first stage of the wavelet transform in a first stage processing element;
• and
• implementing at least two subsequent stages of the wavelet transform in a time-multiplexed manner in a multi-stage processing element;
• wherein the first stage processing element and the multi-stage processing element are each configured to provide both horizontal and vertical filtering of pixel data associated with the image signal.