MPEG-1 Audio

Abstract

MPEG-1 Layer 3 was standardized for the higher sampling rates of 32, 44.1 and 48 kHz in MPEG-1 in 1992.. Figure 1 shows a high level overview of the MPEG-1 Layers I and II coders. The input signal is transformed into 32 subband signals that are uniformly distributed over frequency by means of a critically sampled QMF filterbank. The critically down sampled subband signals are grouped in a so called allocation frame (384 and 1152 subband samples for Layer I and II respectively). By means of Adaptive PCM, these allocation frames are subsequently quantized and coded into an MPEG-1 bitstream. At the decoder side, the bitstream is decoded into the subband samples which are subsequently fed into the inverse QMF filterbank. Figure 1 – High level overview of MPEG-1 Layers I and II coder Next to coding of mono and independent coding of stereo signals, also joint coding of stereo signals is supported by applying a technology called intensity stereo coding. Intensity coding exploits the property of the human auditory system that at high frequencies the perceived stereo image depends on intensity level differences. A block diagram of the Layer 3 encoder algorithm is show in the following diagram: