Methods, systems, apparatuses, and computer programs encoded on computer storage media for performing linear predictive coding (LPC) are described. At least one of a differential spectrum tilt and an energy difference between a current frame and a previous frame of the audio signal is determined. A spectral stability of the audio signal is detected based on at least one of the differential spectrum tilt and an energy difference between the current frame and the previous frame of the audio signal. In response to detecting the spectral stability of the audio signal, quantized LPC parameters for the previous frame are copied into the current frame of the audio signal.