MPEG-1 Layer I to III

The three layers were introduced, so that different requirements on the complexity of the compression can be taken into account. The first layer is the most simple and requires the smallest expenditure for encoding and decoding. Layer III provides the most extensive functionality and achieves the highest quality.

While the MP3 format is wide-spread, layer I and II are hardly used. This is primarily caused by obsolete assumptions about the efficiency of the hardware resources. Due to the fact that a higher layer offers a better quality at the same transfer rate, there is no reason to support the subordinated layers.

Originally layer II coding was used with the DCC (Digital Compact Cassette), which were intended as follow-up system for the analogue cassette (by Philips). The DCC achieved a quality level similar to CD, but could not be established at the market.

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