Decoding method using dynamic scaler factor

A decoding apparatus applied to a convolutionally coded signal, comprising:

• a first soft-in-soft-out (SISO) decoder, decoding the convolutionally coded signal according to systematic information and first a-priori information to generate first extrinsic information;
• a second data converter, converting the first extrinsic information to second a-priori information according to a second scaling factor;
• a second SISO, decoding the convolutionally coded signal according to the systematic information and the second a-priori information to generate second extrinsic information;
• a first data converter, converting the second extrinsic information to the first a-priori information according a first scaling factor;
• a first scaling factor generator, generating one of the first scaling factor and the second scaling factor according to the first a-priori information and the first extrinsic information;
• and
• a second scaling factor generator, generating the other of the first scaling factor and the second scaling factor according to the second a-priori information and the second extrinsic information;
• wherein, one of the first and second SISOs further generates a-posteriori information as a decoding result.