Image coding and decoding methods, image coding and decoding apparatuses, and recording media for image coding and decoding programs
AssigneeMatsushita Electric Industrial Co., Ltd.
InventorChoong Seng Boon
Life of this patent
Estimating the term…
Abstract
In an image coding method of the present invention, after a process such as DCT is performed to digital image data, quantization process is performed, and then, to resultant quantized transform coefficients, variable length coding process is performed with reference to a variable length code table showing how variable length codes are allocated, and in a comparison process between an event derived from the quantized transform coefficients and a reference event included in the variable length code table, transformation process is performed to increase a possibility of performing variable length coding with satisfactory coding efficiency.
Claims4
An image coding method in which variable length coding process is performed to transform coefficients by referring to a variable length code table comprising a plurality of reference events, consisting of Last, Run Level, paired with reference variable length codes, wherein the variable length coding process comprises:
- obtaining an input event consisting of Last Run, Level corresponding to said transform coefficients,
- comparing said input event with a reference event in said table, and if said input event accords with maid reference event, outputting a variable length cede corresponding to said reference event, and if said input event does not accord with any reference events in said table, obtaining a second transformed input event, by transforming the Run value of said input event using a predetermined function,
- comparing said second transformed input event with a reference event in said table, and if said second transformed input event accords with said reference event, outputting a contra code and a third mode code followed by a variable length code corresponding to said reference event,
- and if said second transformed input event doe not accord with any reference events in said table, obtaining a first transformed input event, by transforming the Level value of said input event using a predetermined function,
- comparing said first transformed input event with a reference event in said table, and if said first transforms input event accords with said reference event, outputting a control code and a second mode code followed by a variable length code corresponding to said reference event,
- and if said first transformed input event does not accord with any reference events, outputting a control code an a first mode code followed by a fixed length code corresponding to said input event.
Dependencies are inferred from the claim text.