Pulse-code modulation: Difference between revisions

Revision as of 20:53, 19 September 2024

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{{Modulation techniques}}

'''Pulse-code modulation''' ('''PCM''') is a method used to [[Digital signal (signal processing)|digitally]] represent [[analog signal]]s. It is the standard form of [[digital audio]] in computers, [[compact disc]]s, [[digital telephony]] and other digital audio applications. In a PCM [[Stream (computing)|stream]], the [[amplitude]] of the analog signal is [[Sampling (signal processing)|sampled]] at uniform intervals, and each sample is [[Quantization (signal processing)|quantized]] to the nearest value within a range of digital steps. [[Alec Reeves]], [[Claude Shannon]], [[Bernard M. Oliver|Barney Oliver]] and [[John R. Pierce]] are credited with its invention.<ref>{{Cite book |last=Noll |first=A. Michael |url=https://books.google.com/books?id=rpkuAgAAQBAJ&pg=PA50&dq=pulse+code+modulation+claude+shannon&hlpg=en&newbks=1&newbks_redir=0&source=gb_mobile_search&sa=X&ved=2ahUKEwi2x5n17s-IAxV4g4kEHfFPDto4ChDoAXoECAUQAw#v=onepage&q&f=falsePA50 |title=Highway of Dreams: A Critical View Along the Information Superhighway |date=1997 |publisher=Erlbaum |isbn=978-0-8058-2557-2 |edition=Revised |series=Telecommunications |___location=Mahwah, NJ |pages=50 |language=en}}</ref><ref>{{Cite web |last=Leibson |first=Steven |date=2021-09-07 |title=A Brief History of the Single-Chip DSP, Part I |url=https://www.eejournal.com/article/a-brief-history-of-the-single-chip-dsp-part-i/ |access-date=2024-09-19 |website=EEJournal |language=en-US}}</ref><ref>{{Cite book |last=Barrett |first=G. Douglas |url=https://books.google.com/books?id=r9-SEAAAQBAJ&pg=PA102&dq=Audio+Engineering+claude+shannon&hlpg=en&newbks=1&newbks_redir=0&source=gb_mobile_search&sa=X&ved=2ahUKEwiFmJ3_5c-IAxVxlokEHS9MNKY4HhDoAXoECAIQAw#v=onepage&q&f=falsePA102 |title=Experimenting the Human: Art, Music, and the Contemporary Posthuman |date= |publisher=[[The University of Chicago Press]] |year=2023 |isbn=978-0-226-82340-9 |___location=Chicago London |pages=102 |language=en}}</ref>

'''Linear pulse-code modulation''' ('''LPCM''') is a specific type of PCM in which the quantization levels are linearly uniform.<ref name="LOC_LPCM" /> This is in contrast to PCM encodings in which quantization levels vary as a function of amplitude (as with the [[A-law algorithm]] or the [[μ-law algorithm]]). Though ''PCM'' is a more general term, it is often used to describe data encoded as LPCM.