DocumentCode :
1149510
Title :
Mistracking in successive PCM/ADPCM transcoders
Author :
Bonnet, Madeleine ; Macchi, Odile ; Jaidane-Saidane, Meriem
Author_Institution :
CNRS-ESE, Gif-sur-Yvette, France
Volume :
37
Issue :
8
fYear :
1989
fDate :
8/1/1989 12:00:00 AM
Firstpage :
843
Lastpage :
850
Abstract :
An analysis is presented of the causes of the accumulation of quantizing noise found in the transient state for successive CCITT adaptive differential pulse-code-modulation (ADPCM) transcoders connected synchronously. By decoupling the predictor and quantizer effect it is proved that, owing to a self-stabilization phenomenon, narrowband inputs cause local instabilities in the predictor of the jointly adaptive autoregressive moving-average-prediction/quantization used in the ADPCM 32-kb/s algorithm. Despite the assured global stability, these local instabilities are not synchronized at the encoder and its preceding decoder, and a mistracking occurs which creates quantizing noise accumulation. The tracking is then shown to be very sensitive to predictor/quantizer interaction. The discontinuities introduced in the standardized adaptive quantizer extend the mistracking problem to wideband inputs. A smoothed quantizer with reduced inauspicious interaction is proposed to remedy the problem
Keywords :
decoding; encoding; pulse-code modulation; 32 kbit/s; CCITT system; adaptive differential pulse-code-modulation; decoder; encoder; jointly adaptive autoregressive moving-average-prediction/quantization; local instabilities; mistracking; narrowband inputs; predictor; quantizer; quantizing noise accumulation; self-stabilization phenomenon; smoothed quantizer; successive PCM/ADPCM transcoders; wideband inputs; Algorithm design and analysis; Decoding; Narrowband; Phase change materials; Quantization; Repeaters; Signal analysis; Signal to noise ratio; Speech; Transcoding;
fLanguage :
English
Journal_Title :
Communications, IEEE Transactions on
Publisher :
ieee
ISSN :
0090-6778
Type :
jour
DOI :
10.1109/26.31183
Filename :
31183
Link To Document :
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