Audio codec and built-in self test method for the same

An audio codec and a BIST method adapted for the audio codec are provided. The BIST method includes the following steps. A first channel digital-to-analog converter (DAC) of the audio codec converts a test signal into an analog signal. A first channel analog-to-digital converter (ADC) of the audio codec converts the analog signal into a digital signal. Use a second channel DAC of the audio codec and a second channel ADC of the audio codec to calculate the magnitudes of a plurality of spectral components of the DFT of the digital signal. Determine whether the audio codec passes the test according to the magnitudes of the spectral components.