Context-based arithmetic encoding apparatus and method and context-based arithmetic decoding apparatus and method

A method of noiseless-decoding a 2-tuple which is a combination of two spectral coefficients, the method comprising:

• determining a first context of an input signal including audio or speech, based on a neighboring 2-tuple of a current 2-tuple;
• decoding a most significant bit (MSB) of the current 2-tuple, by using a first probability table obtained from the first context, wherein the neighboring 2-tuple is previously decoded prior to the current 2-tuple;
• determining, performed by at least one processing device, a second context of the input signal including the audio or the speech based on information indicating whether at least one non-zero bit is included in decoded bits of a spectral coefficient;
• decoding a least significant bit (LSB) of the current 2-tuple, by using a second probability table obtained from the second context;
• and
• generating quantized spectral coefficients of the current 2-tuple based on the decoded MSB and the decoded LSB,
• wherein
• the first context is different from the second context.