Adaptive block size image compression method and system

In an adaptive block size compression system wherein a block of pixel data is transformed to AC and DC discrete cosine transform (DCT) coefficient data for a block and at least one constituent level of sub-blocks of pixel data, and wherein the AC and DC DCT coefficient values of a composite block of selected ones of said block and constituent sub-blocks of pixel data are provided for transmission, a method for compressing said DC DCT coefficient values comprising:

• receiving at least one block of data;
• performing a series of discrete cosine transformation (DCT) operations to provide AC and DC DQT coefficient values with a first DCT operation performed on said at least one block of data to provide first sub-blocks of AC and DC DQT coefficient values and at least one additional DCT operations is performed on sub-blocks of selected DC DQT coefficient values resultant from a preceding DCT operation of said series of DCT operations;
• and
• selecting ones of AC and DC DQT coefficient values resultant from said first DCT operation and said at least one additional DCT operation to provide a DQT composite block of AC and DC DQT coefficient values.

An image compression apparatus for compressing data representative of a block of pixel data comprising:

• transform means for receiving an input block of pixel data and performing a discrete cosine transform (DCT) operation on said block of pixel data and on at least one predetermined level of constituent sub-blocks of pixel data thereof to provide corresponding AC and DC DCT coefficient values for said block and constituent sub-blocks and selecting ones of said AC and DC DCT coefficient values to provide a composite block of AC and DC DCT coefficient values representing said input block of pixel data;
• DC DCT compression means for compressing the DC DCT values of said composite block of AC and DC DCT coefficient values by performing a series of DCT operations to provide AC and DC DQT coefficient values, with a first DCT operation performed on sub-blocks of said DC DQT values of said constituent sub-blocks of pixel data and additional DCT operations performed on sub-blocks of DC DQT values from preceding DCT operations of said series of DCT operations and encoding ones of said AC and DC DQT coefficient values to provide compressed DC DCT coefficient values;
• and
• combination means for receiving said composite block of AC and DC DCT and said compressed DC DCT coefficient values and combining said composite block of AC and DC DCT and said compressed DC DCT coefficient values to provide a composite block of AC and compressed DC DCT coefficient values.

A method for compressing image data for a block of pixel data comprising the steps of:

• receiving an input block of pixel data;
• performing a discrete cosine transform (DCT) operation on said block of pixel data and on at least one predetermined level of constituent sub-blocks of pixel data thereof to provide corresponding AC and DC DCT coefficient values for said block and constituent sub-blocks;
• selecting ones of said AC and DC DCT coefficient values to provide a composite block of AC and DC DCT coefficient values representing said input block of pixel data;
• performing a series of DCT operations on said DC DCT coefficient values for said constituent sub-blocks to provide AC and DC DQT coefficient values, with a first DCT operation performed on said DC DCT values of said constituent sub-blocks of pixel data and additional DCT operations performed on sub-blocks of DC DQT values from preceding DCT operations of said series of DCT operations;
• encoding ones of said AC and DC DQT coefficient values to provide compressed DC DCT coefficient values;
• and
• combining said composite block of AC and DC DCT and said compressed DC DCT coefficient values to provide a composite block of AC and compressed DC DCT coefficient values.

In an image decoder wherein an image block of pixel data is processed by performing a discrete cosine transform (DCT) operation on said block of pixel data and on at least one predetermined level of constituent sub-blocks of pixel data thereof to provide corresponding block and sub-blocks of AC and DC DCT coefficient values, and wherein said DC DCT coefficient values are compressed by performing a series of DCT operations performed on said DC DCT coefficient values of said sub-blocks of pixel data to provide AC and DC DQT coefficient values with a first of said series of DCT operations performed on said sub-blocks of DC DCT coefficient values with at least one additional DCT of said series of additional DCT operations performed on selected sub-blocks of said DC DCT coefficient values and said DC DQT of previous DCT operations of said series of DCT operations to provide a composite block of AC and DC DQT coefficient values, and wherein selected values of said composite block of AC and DC DQT coefficient values are encoded to provide compressed DC DCT coefficient values, and wherein a signal is provided indicative of said compressed DC DCT coefficient values and selected ones of said block and sub-blocks of AC and DC DCT coefficient values, an apparatus for decoding said compressed DC DCT coefficient values comprising:

• separator means for receiving said signal indicative of said compressed DC DCT coefficient values and selected AC DCT values of said block and sub-blocks of AC and DC DCT coefficient values and providing a signal indicative of said compressed DC DCT coefficient values in accordance with a predetermined separation format;
• decoder means for receiving said signal indicative of said compressed DC DCT coefficient values and providing said decoded DC DCT coefficient values in accordance with a predetermined decoding format;
• and
• inverse discrete quadtree means for receiving said decoded DC DCT coefficient values, performing a series of inverse discrete cosine transformation (IDCT) operations to provide AC and DC IDCT coefficient values with a first IDCT performed on selected values of said processed DC DCT coefficient values and additional IDCT operations performed on additional selected values of said processed DC DCT coefficient values and resultant AC and DC IDCT values from preceding IDCT operations and wherein ones of said AC and DC IDCT coefficient values are provided as said DC DCT coefficient values.

In an image decoder wherein an image block of pixel data is processed by performing a discrete cosine transform (DCT) operation on said block of pixel data and on at least one predetermined level of constituent sub-blocks of pixel data thereof to provide corresponding block and sub-blocks of AC and DC DCT coefficient values, and wherein said DC DCT coefficient values are compressed by performing a series of DCT operations performed on said DC DCT coefficient values of said sub-blocks of pixel data to provide AC and DC DQT coefficient values with a first of said series of DCT operations performed on said sub-blocks of DC DCT coefficient values with at least one additional DCT of said series of additional DCT operations performed on selected sub-blocks of said DC DCT coefficient values and said DC DQT coefficient values of previous DCT operations of said series of DCT operations to provide a composite block of AC and DC DQT coefficient values, and wherein selected values of said composite block of AC and DC DQT coefficient values are encoded to provide compressed DC DCT coefficient values, and wherein a signal is provided indicative of said compressed DC DCT coefficient values and selected ones of said block and sub-blocks of AC and DC DCT coefficient values, a method for decoding said compressed DC DCT coefficient values comprising the steps of:

• receiving said signal indicative of a composite block of AC and compressed DC coefficient values;
• providing compressed DC coefficient values from said composite block of AC and compressed DC coefficient values in accordance with a predetermined separation format;
• decoding compressed DC coefficient values accordance with a predetermined decoding format to provide decoded DC DCT coefficient values;
• and
• performing a series of inverse discrete cosine transformation (IDCT) operations to provide AC and DC IDCT coefficient values with a first IDCT performed on blocks of selected values of said compressed DC DCT coefficient values and additional IDCT operations performed on additional selected values of said compressed DC DCT coefficient values and resultant AC and DC IDCT values from preceding IDCT operations of said series of IDCT operations.

In an image decoder wherein an image block of pixel data is processed by performing a discrete cosine transform (DCT) operation on said block of pixel data and on at least one predetermined level of constituent sub-blocks of pixel data thereof to provide corresponding block and sub-blocks of AC and DC DCT coefficient values, performing a series of additional DCT operations on said sub-blocks of DC DCT coefficient values with additional DCT operations performed on selected sub-blocks of said DC DCT coefficient values and resultant DC DCT of previous DCT operations of said series of DCT operations to provide a composite block of AC and DC DQT coefficient values, encoding selected values of said composite block of AC and DC DQT coefficient values to provide compressed DC DCT coefficient values and combing selected ones of said block and sub-blocks of AC and DC DCT coefficient values and said compressed DC DCT coefficient values to provide a signal indicative of a compressed block of AC and compressed DC coefficient values, an apparatus for decoding said processed DC DCT coefficient values comprising:

• separator means for receiving said signal indicative of a composite block of AC and compressed DC coefficient values and separating a signal indicative of said processed DC DCT coefficient values from said signal indicative of a compressed block of AC and compressed DC coefficient values in accordance with a predetermined separation format;
• decoder means for receiving said signal indicative of said processed DC DCT coefficient values and providing said processed DC DCT coefficient values in accordance with a predetermined decoding format;
• inverse discrete quadtree means for receiving said processed DC DCT coefficient values, performing a series of inverse discrete cosine transformation (IDCT) operations to provide AC and DC IDCT coefficient values with a first IDCT performed on selected values of said processed DC DCT coefficient values and additional IDCT operations performed on additional selected values of said processed DC DCT coefficient values and resultant AC and DC IDCT values from preceding IDCT operations;
• combination means for receiving said AC DCT coefficient values and said DC IDCT coefficient values to provide a composite block of AC and decoded DC coefficient values and
• inverse transform for performing at least one IDCT operation on said composite block of AC and decoded DC coefficient values to provide a composite pixel block.

A method for decoding a block of pixel data wherein an image block of pixel data is processed by performing a discrete cosine transform (DCT) operation on said block of pixel data and on at least one predetermined level of constituent sub-blocks of pixel data thereof to provide corresponding block and sub-blocks of AC and DC DCT coefficient values, performing a series of additional DCT operations on said sub-blocks of DC DCT coefficient values with additional DCT operations performed on selected sub-blocks of said DC DCT coefficient values and resultant DC DCT of previous DCT operations of said series of DCT operations to provide a composite block of AC and DC DQT coefficient values, encoding selected values of said composite block of AC and DC DQT coefficient values to provide compressed DC DCT coefficient values and combining selected ones of said block and sub-blocks of AC and DC DCT coefficient values and said compressed DC DCT coefficient values to provide a signal indicative of a compressed block of AC and compressed DC coefficient values, a method for decoding said block of pixel data comprising the steps of:

• receiving said signal indicative of a composite block of AC and compressed DC coefficient values;
• providing said compressed DC coefficient values of said composite block of AC and compressed DC coefficient values;
• separately providing said AC coefficient values of said composite block of AC and compressed DC coefficient values;
• decoding said compressed DC DCT coefficient values in accordance with a predetermined decoding format to provide decoded DC DCT values;
• performing a series of inverse discrete cosine transformation (IDCT) operations to provide AC and DC IDCT coefficient values with a first IDCT performed on blocks of selected values of said processed DC DCT coefficient values and additional IDCT operations performed on blocks of selected values of said processed DC DCT coefficient values and resultant AC and DC IDCT values from preceding IDCT operations wherein ones of said AC and DC IDCT values and decoded DCT values are provided as uncompressed DC DCT coefficient values;
• and
• combining said AC DCT coefficient values and said uncompressed DC DCT coefficient values to provide a composite block of AC and uncompressed DC coefficient values;
• and
• performing at least one IDCT operation on said composite block of AC and uncompressed DC coefficient values to provide a composite pixel block.

In an adaptive block size compression system wherein a block of pixel data is transformed to AC and DC discrete cosine transform (DCT) coefficient data for constituent blocks of vary block size, a sub-system for compressing said DC DCT coefficient data comprising:

• discrete quadtree means having a first input for receiving at least one block of data and having an output wherein said discrete quadtree means comprises:
• plurality of DCT means with a first DCT means having an input for receiving said at least one block of data and having an output with each additional DCT means having an input and an output;
• and
• at least one selector means disposed between each of said plurality of DCT means having and input coupled to a corresponding DCT means output and output coupled to a corresponding one of said additional DCT means input;
• and
• selection means having an input coupled to said discrete quadtree means output and having an output.

In an image decoder wherein and image block of pixel data is processed by performing a discrete cosine transform (DCT) operation on said block of pixel data and on at least one predetermined level of constituent sub-blocks of pixel data thereof, and providing corresponding block and sub-blocks of AC and DC DCT coefficient values and wherein said DC DCT coefficient values is further processed by performing a series of at least one additional DCT operation on said sub-blocks of DC DCT coefficient values, a subsystem for decoding said processed DC DCT coefficient values comprising:

• decoder means having an input for receiving a signal indicative of said processed DC DCT coefficient values and having an output;
• and
• inverse discrete quadtree means having an input coupled to said decoder means output, wherein said inverse discrete quadtree means comprises:
• plurality of separator means with a first separator means having an input for receiving said signal indicative of said processed DC DCT coefficient values and additional separator means having an input and an output;
• at least one inverse discrete means disposed between said plurality of separator means having an input coupled to a corresponding separator means output.