Audio Coding Using Perceptually Controlled Bitstream Buffering

Perceptual audio coders use a varying number of bits to encode subsequent frames according to the perceptual entropy of the audio signal. For transmission over a constant bitrate channel the bitstream must be buffered. The buffer must be large enough to absorb variations in the bitrate, otherwise the quality of the audio will be compromised. We present a new scheme for buffer control of perceptual audio coders. In contrast to conventional schemes the proposed scheme systematically reduces the variation in a perceptual distortion measure over time. The new scheme applied to a perceptual audio coder (PAC) improves the quality of the encoded signal for a given buffer size. The same technique can be used to increase the performance of other coders such as MPEG-1 Layer III or MPEG-2 AAC while maintaining backward compatibility.