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Re: [Q]Are the ADPCM and the PCM lossy or lossless???

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On Saturday, April 10, 1999 at 12:30:00 PM UTC+5:30, Joseph S. Wisniewski wrote:
> "Baik, Seong-bok" wrote:
> > 
> > Usually, the PCM seems to be thought as lossless, but most people
> > say the ADPCM is lossy. Could anyone please tell me why?
> > 
> > Thanks in advance...
> 
> PCM (Pulse Code Modulation) is loseless becuase it's not a data
> compression method. It's just simply the storage or transmission of the
> raw values (the Code for the Pulse) that come from an A/D converter.
> 
> ADPCM (Adaptive Differential PCM) takes the differential of a PCM signal
> (the difference between successive samples). At this point, you haven't
> actually lost any information yet, since the difference between two 16
> bit samples is (technically) a 17 bit number. The "lossy" part comed
> from the "adaptive" slgorithm. An adaptive scaling factor is applied to
> these differences, to get them down to 4 bit numbers (well, some ADPCM
> schemes use from 2 to 6 bit numbers, but 4 is most common). When the
> scaling factor is small, you capture low level changes in the signal
> well (and most any low frequency data) but high level, high speed
> transients (large values of high frequency components) will distort
> because you don't have enough dynamic range to track them, so you run
> into a slew rate limit (clipping of the differential). When the adaptive
> scaling factor is large, you capture large dynamice well, but small
> variations are distorted, since the quantitization step size is too
> large, and you get quantitization noise. So the signal you get back
> almost always looses some information.
> 
> Hope this helps.
> 
> Joe

if any system using quantizer then it will be definitely lossy  

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Re: [Q]Are the ADPCM and the PCM lossy or lossless??? amitvec1014@gmail.com - 2015-07-24 22:17 -0700

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