I implemented a simple clone of mp3 and it was not that hard. If you do a discrete Fourier transform of the audio (in small overlapping windows), quantize the r

I implemented a simple clone of mp3 and it was not that hard. If you do a discrete Fourier transform of the audio (in small overlapping windows), quantize the resulting coefficients, and compress them losslessly using the Huffman codes, you will end up with something not that far from mp3. The human ear is quite forgiving to the effects of quantization in frequency domain. MP3 does not have remarkable fidelity though. MP3, and my clone of it, suffers from time domain artifacts. Quantization in the frequency domain causes distortion in the time domain as well, negatively affecting high frequency transient sounds like cymbals. That is more noticeable. Newer generation codecs like AAC handle transients much better, but they are considerably more advanced, and often use different transforms like wavelet transform.