Sub-band coding

Such quantization errors may be thought of as a type of noise, because they are effectively the difference between the original source and its binary representation.

In effect, many bits are wasted in encoding masked portions of the signal because PCM makes no assumptions about how the human ear hears.

Using 8-bit mu-law encoding would cut the per-channel bitrate of CD audio down to about 350 kbit/s, half the standard rate.

Because this simple method only minimally exploits masking effects, it produces results that are often audibly inferior compared to the original.

The final step is to format all these quantized samples into groups of data called frames, to facilitate eventual playback by a decoder.

The frames are unpacked, subband samples are decoded, and a frequency-time mapping reconstructs an output audio signal.