Fast time-frequency transform algorithms and their applications to real-time software implementation of AC-3 audio codec

AC-3 audio coding technology is a kind of perceptual audio coder (PAC) developed by the Dolby Company. Up to 5 full-bandwidth channels and one subwoofer channel (cutoff at 120 Hz) are available in AC-3 to provide multi-channel, low bit rate, and high perceptual quality of audio. This explains why AC-3 has become the audio standard of many international standards. In this paper, we focus on the real-time software implementation issues of AC-3. Two fast algorithms of the time-frequency transform, one for memory economization and the other is for time domain subsampling, are presented. Meanwhile, we state the current performance status of our AC-3 decoder.