TI window compression/expansion method

A method of compressing and expanding the window tables of any transform based audio decoder comprising the steps of:

• sampling a window of data a predetermined number of times and yielding a first few of window sample values and the rest of window sample values;
• providing a window compression filter, having more than one stage and each stage having an initial state variable of an initial value prior to execution of said filter;
• providing a compressed window table in memory for storing at least said first few of window sample values and said initial state variables of said window compression filter;
• differentially encoding said rest of window sample values in said window compression filter and storing said compressed window samples in said compressed window table;
• providing an available buffer in memory;
• providing a window expansion filter, having more than one stage and each stage having an initial state variable;
• storing said first few window samples in said buffer;
• setting said window expansion filter initial state variables to the initial values of the initial state variable of said window compression filter;
• expanding said compressed window samples in said window expansion filter, yielding expanded window samples and storing said expanded window samples in said buffer along with said first few window samples;
• and
• outputting said buffer contents once a window.

The structure of a window table compressor of a transform based audio encoder comprising:

• a predetermined number of window sample values of a window of data yielding a first few of window sample values and the rest of window sample values;
• a window compression filter, having more than one stage and each stage having an initial state variable, prior to execution of said filter;
• a compressed window table in memory for storing at least said first few of window sample values and said initial state variables of said window compression filter;
• and;
• wherein said window compression filter differentially encodes said rest of window sample values and storing said differentially encoded window samples in said compressed window table.