Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!psuvax1!psuvm!auvm!ITD!ADAMSON From: adamson@ITD.NRL.NAVY.MIL (Brian Adamson) Newsgroups: bit.listserv.emusic-l Subject: Re: pcm data Message-ID: <9002121420.AA23123@css.itd.nrl.navy.mil> Date: 12 Feb 90 14:20:17 GMT Sender: Electronic Music Discussion List Reply-To: Electronic Music Discussion List Lines: 27 Approved: NETNEWS@AUVM Gateway X-To: EHARNDEN%AUVM.BITNET@PSUVM.PSU.EDU X-cc: EMUSIC-L%AUVM.BITNET@PSUVM.PSU.EDU Pulse code modulation is just a description of how the analog was sampled into a digital signal. People use thsi term in a general (perhaps incorrect) sense when talking about analog-to-digital conversion. Other techniques to do A/D conversion besides PCM could include continuous delta conversion techniques. As far as linear is concerned, that just refers to the fact that there is relationship (mathematically) between the digital data and the analog signal is linear. For example non-linear would indicate that some sort of companding or compression rule had been used when A/D converting the analog signal. An example of this is mu-law or A-law mapping which is used for speech. By optimizing the fit of the digital data to the particualar analog signal (speech) using empirical data, 8 bit analog-to-digital conversion can sound like 12 bit (but only for speech using mu-law or A-law) This is due to the fact that the human ear doesn't necessarily respond in a linear fashion to sound. Of course these mappling rules don't preserve the dynamic range of the input signal (O.K. for speech) so probably want to maintain a linear representation of the analog signal when sampling for hi-fi music purposes. Hope this helps, Brian Adamson