Regarding MPEG audio coding, what are “Layers 1, 2 and 3”?
MPEG standards describe the compression of audio signals using high performance perceptual coding schemes. MPEG specifies a family of three audio coding schemes called Layer -1, -2, and -3. Each scheme has increasing encoder complexity and performance (sound quality per bitrate) from Layer 1 through 3. Each of the three codecs are compatible in a hierarchical way; a Layer-n decoder is able to decode bitstream data encoded in its layer and in all layers below it. For example, a Layer-2 decoder will understand layers 2 and 1, although a Layer-1 decoder will only accept Layer-1. Layer -2 as used in ClipMail Pro and ClipMail ProView is commonly used for high quality industrial applications (for example satellite DSS and CD audio).
