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In article <7070001@hpindda.HP.COM> rbean@hpindda.HP.COM (Rich Bean) writes:
>> *ADPCM -probably Analog to Digital, Pulse Code Modulation
>> -C. Fogg
>
>I think ADPCM might be:
>  Adaptive Delta Pulse Code Modulation
>
>Delta means it encodes the difference between successive samples, which
>usually takes fewer bits than the samples themselves.  Adaptive might
>have something to do with changing resolution to match the input stream,
>using the fewest bits possible ... but I'm not sure about that.
>
>Rich Bean     rbean@hpindbu

	ADPCM stands for Adaptive Differential Pulse Code Modulation.
	"Pulse Code Modulation" refers to the fact that the input 
	signal has been sampled and quantized into N (generally 8 )
	bits per samples. "Differential" means that what is quantized 
	is the difference between two successive samples rather 
	than the samples themselves. More precisely, "Differential" 
	can involve the difference of the current input sample with the 
	output of a prediction filter. "Adaptive" means that the 
	predictor coefficients ( the prediction filter ) can  be 
	readjusted by measuring statistics of the incoming samples. 
	"Pulse Code Modulation" and "Delta Modulation" are both 
	well known digital signal processing techniques; So are 
	"Differential Pulse Code Modulation" (PCM) and "Adaptive 
	Differential Pulse Code Modulation" (ADPCM). See any textbook 
	on Digital Communication. I have never heard of "Adaptive 
	Delta Pulse Code Modulation".

			Regis J. CRINON
			Digital Signal and Picture Processing Group
			TEKLABS
			TEKTRONIX INC.




-- 
crinon