Editing Companding (section)

==History==
The use of companding in an analog picture transmission system was patented by A. B. Clark of [[American Telephone & Telegraph|AT&T]] in 1928 (filed in 1925):<ref>{{Ref patent
 |country= US
 |number=
 |status= patent
 |title= [https://patents.google.com/patent/US1691147 Electrical picture-transmitting system]
 |gdate= 1928-11-13
 |fdate= 1925-06-06
 |inventor= A. B. Clark
 |invent1= Clark, A. B.
 |assign1= AT&T
}}</ref>

{{blockquote|In the transmission of pictures by electric currents, the method which consists in sending currents varied in a non-linear relation to the light values of the successive elements of the picture to be transmitted, and at the receiving end exposing corresponding elements of a sensitive surface to light varied in inverse non-linear relation to the received current.|A. B. Clark patent}}

In 1942, Clark and his team completed the [[SIGSALY]] secure voice transmission system that included the first use of companding in a PCM (digital) system.<ref>{{cite book | title = Wireless Security: Models, Threats, and Solutions | author = Randall K. Nichols and Panos C. Lekkas | publisher = McGraw-Hill Professional | year = 2002 | isbn = 0-07-138038-8 | url = https://archive.org/details/wirelesssecurity00nich| url-access = registration | page = [https://archive.org/details/wirelesssecurity00nich/page/256 256] | quote = companding a-b-clark pcm. }}</ref>

In 1953, B. Smith showed that a nonlinear DAC could be complemented by the inverse nonlinearity in a [[successive-approximation ADC]] configuration, simplifying the design of digital companding systems.<ref>B. Smith, "Instantaneous Companding of Quantized Signals," ''Bell System Technical Journal'', Vol. 36, May 1957, pp. 653–709.</ref>

In 1970, H. Kaneko developed the uniform description of segment (piecewise linear) companding laws that had by then been adopted in digital telephony.<ref>H. Kaneko, "A Unified Formulation of Segment Companding Laws and Synthesis of Codecs and Digital Compandors," ''Bell System Technical Journal'', Vol. 49, September 1970, pp. 1555–1558.</ref>

In the 1980s and 1990s, many of the music equipment manufacturers ([[Roland Corporation|Roland]], [[Yamaha Corporation|Yamaha]], [[Korg]]) used companding when compressing the library waveform data in their [[digital synthesizer]]s. However, exact algorithms are unknown, neither if any of the manufacturers ever used the Companding scheme which is described in this article. The only known thing is that manufacturers did use data compression<ref>{{Cite web |title=Gearspace - View Single Post - Why is My Hardware Sampler Sounding Better Than My Software Sampler!? Same Samples!.. |url=https://gearspace.com/board/showpost.php?p=5446278&postcount=130 |access-date=2024-10-25 |website=gearspace.com |language=en}}</ref> in the mentioned time period and that some people refer to it as ''companding'' while in reality it might mean something else, for example data compression and expansion.<ref>{{Cite web |title=Gearspace - View Single Post - Roland JV-1080 vst plugin |url=https://gearspace.com/board/showpost.php?p=13068220&postcount=146 |access-date=2024-10-25 |website=gearspace.com |language=en}}</ref> This dates back to the late '80s when memory chips were often one of the most costly components in the instrument. Manufacturers usually quoted the amount of memory in its compressed form: i.e. 24 MB of physical waveform ROM in a [[Korg Trinity]] is actually 48 MB when uncompressed. Similarly, Roland SR-JV expansion boards were usually advertised as 8 MB boards with '16 MB-equivalent content'. Careless copying of this technical information, omitting the ''equivalence'' reference, can often cause confusion.