Electrical audio signal processing systems and devices – One-way audio signal program distribution – Public address system
Patent
1989-11-27
1992-04-14
Shaw, Dale M.
Electrical audio signal processing systems and devices
One-way audio signal program distribution
Public address system
381 37, G10L 704, G10L 918
Patent
active
051054639
ABSTRACT:
A system for subband coding of a digital audio signal x(k) includes in the coder (1) a filter bank (3) for splitting the audio signal band, with sampling rate reduction, into subbands (p=1, . . . P) of approximately critical bandwidth and in the decoder (2) a filter bank (5) for merging these subbands, with sampling rate increase. For each subband (p) the coder (1) comprises a detector (7(p)) for determining a parameter G(p;m) representative of the signal level in a block (p;m) of M samples of the subband signal x.sub.p (k) as well as a quantizer (8(p)) for adaptively block quantizing this subband signal in response to parameter G(p;m), and the decoder (2) comprises a dequantizer (9(p)) for adaptively block dequantizing the quantized subband signal s.sub.p (k) in response to parameter G(p;m). The quantizing characteristics are related to the noise-masking curve of the human auditory system, owing to which a high-quality of the replica x(k) of audio signal x(k) is attained with an average number of approximately 2.5 bits per sample for representing the output signals of the coder (1). The occasional audibility of quantizing noise in this replica x(k) is reduced effectively in that the coder (1) and decoder (2) contain identical bit allocation means (23, 24) responsive to a set of parameters G(p;m) for the higher group of subbands (p.sub.im .ltoreq.p.ltoreq.P) within an allocation window (FIG. 5) for allocating a number of B(p;m) bits per sample from a fixed predetermined number of B bits for this allocation window to the quantizer (8(p)) and the dequantizer (9(p)) for the block (p;m) of subband signal x.sub.p (k) and s.sub.p (k), respectively.
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Breeuwer Marcel
Van Der Waal Robbert G.
Veldhuis Raymond N. J.
Eason Leroy
Knepper David D.
Shaw Dale M.
U.S. Philips Corporation
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