An AudioCodec Based on the Perceptual Equality between the Original and Restored Audio Signals

A method for lossy audio data compression (AudioCodec) is presented. It allows for improving objective quality of the restored audio signal by 25% at a bitrate of 390 kbps and 55% at a bitrate of 64 kbps compared to the AAC MPEG-4 format. The proposed method of audio data compression is based on an advanced theory of lossy audio data compression (TLAC), which is also introduced in the article. The improvement in the objective quality of the reconstructed audio signal (according to the standardized PEAQ measure) is achieved because the TLAC overcomes issues in modern lossy audio data compression methods related to the use of psychoacoustic principles of human sound perception, including after overcoming the "psychoacoustic compression limit" of the audio signal (i.e. the moment in perceptual coding when the available bit budget is insufficient to encode all spectral components with the accuracy required from a psychoacoustic perspective). This allows for achieving perceptual equality between the original and reconstructed audio signals. As an analysis of the state of the art, solutions for both lossless and lossy audio data compression, as well as those using artificial intelligence, are considered. In all modern lossy audio data compression methods, the procedure for selecting the spectral components to be preserved, as well as the permissible quantization error, is carried out through a series of highly complex procedures collectively referred to as the "psychoacoustic model of the lossy audio compression method". In a strict sense, perceptual equality between the spectra of the original and restored signals has not been proven by any research group and, therefore, cannot be guaranteed by them. Independent experts regularly publish tests demonstrating that modern audio codecs have issues with certain audio signals. The article proposes an AudioCodec based on the perceptual equality between the original and restored audio signals, which is based on the new ideas of the theory of lossy audio compression (TLAC). These ideas guarantee the achievement of perceptual equality between the original and restored audio signals at different bitrates, therefore, the AudioCodec built on its basis is free from the above-mentioned issues and, as a result, significantly outperforms modern AudioCodecs in terms of the objective quality of the restored audio signal, as measured by PEAQ.