Pulse Code Modulation - Revision history

Porcuswiki: Float. Navbox, because users might have navigated here using it.

2024-05-19T13:24:02Z

Float. Navbox, because users might have navigated here using it.

← Older revision		Revision as of 13:24, 19 May 2024
Line 8:		Line 8:


	=== Linear PCM ===		== Linear PCM ==
	In ''Linear'' PCM, the quantization levels are linear in amplitude. To visualize, each 16-bit sample of CD audio represents the amplitude as a number between −32768 and 32767 in ''equidistant'' steps: a difference from 2 to 11 makes for the same as the difference from 13000 to 13009. Linear PCM can be converted with ordinary multi-bit converters: the 12th bit contributes the same to the analog signal no matter what the other bits are. Consumer-audio "digital output" connections like S/PDIF (coaxial or TOSlink optical, the latter more common from computer motherboards) and audio over HDMI (although other encodings might be transferred as well).		In ''Linear'' PCM, the quantization levels are linear in amplitude. To visualize, each 16-bit sample of CD audio represents the amplitude as a number between −32768 and 32767 in ''equidistant'' steps: a difference from 2 to 11 makes for the same as the difference from 13000 to 13009. Linear PCM can be converted with ordinary multi-bit converters: the 12th bit contributes the same to the analog signal no matter what the other bits are. Consumer-audio "digital output" connections like S/PDIF (coaxial or TOSlink optical, the latter more common from computer motherboards) and audio over HDMI (although other encodings might be transferred as well).

	As a counterexample formed by modifying a PCM signal with a nonlinearity: [[High_Definition_Compatible_Digital\|HDCD]]'s low level adjustment can flag the lower bits to signify something else if the signal is close to zero (i.e., depending on the more significant bits), and its peak extension is also a nonlinearity. A non-HDCD-aware DAC will omit these steps, and decode linearly - the DAC will receive as 'PCM', as the flags are hidden in the signal.		As a counterexample formed by modifying a PCM signal with a nonlinearity: [[High_Definition_Compatible_Digital\|HDCD]]'s low level adjustment can flag the lower bits to signify something else if the signal is close to zero (i.e., depending on the more significant bits), and its peak extension is also a nonlinearity. A non-HDCD-aware DAC will omit these steps, and decode linearly – the DAC will receive as 'PCM', as the flags are hidden in the signal.

	=== Differential PCM ===		=== Integer vs floating-point LPCM ===
			The WAVE and AIFF formats offer both 32-bit integer (like the 16-bit example above, except with the much bigger range -2147483648 to 2147483647) and
			32/64-bit floating-point PCM formats. 32-bit floating-point represents numbers in the [https://en.wikipedia.org/wiki/Single-precision_floating-point_format IEEE 754 floating-point format]; in simplified terms, it is 24 bit integer augmented with a giant volume control acting on each sample. IEEE 754 is a general-purpose format, and the "volume control" happens to be a veritable overkill for audio purposes; it makes floating-point format is thus immune to clipping for all purposes except deliberately running hundreds of dB off.

			End-users acquiring a "32-bit" WAVE (or AIFF) file might sometimes encounter compatibility issues from confusing the two. 32-bit integer and 32-bit float do not have much in common except the "32", which is how much space is spent storing a sample. Conversion between the two is not [[lossless]] either way, and in particular, ffmpeg might clip when converting from float.


			== Differential PCM ==
	''Differential'' PCM will, in simplified terms, encode the difference between consecutive samples. The ''adaptive differential PCM'' ([[ADPCM]]) variant is common in e.g. telecommunication, where the signal is typically companded using given nonlinear functions specified as A-law<ref>https://en.wikipedia.org/wiki/A-law_algorithm</ref> and µ-law<ref>https://en.wikipedia.org/wiki/%CE%9C-law_algorithm</ref> (wikipedia links).		''Differential'' PCM will, in simplified terms, encode the difference between consecutive samples. The ''adaptive differential PCM'' ([[ADPCM]]) variant is common in e.g. telecommunication, where the signal is typically companded using given nonlinear functions specified as A-law<ref>https://en.wikipedia.org/wiki/A-law_algorithm</ref> and µ-law<ref>https://en.wikipedia.org/wiki/%CE%9C-law_algorithm</ref> (wikipedia links).


	=~~= References ==~~		= Further reading =
	~~<references/>~~

	~~== See also =~~=

	* [[Pulse-Density Modulation]] (PDM)		* [[Pulse-Density Modulation]] (PDM)
	* [[Pulse-Amplitude Modulation]] (PAM)		* [[Pulse-Amplitude Modulation]] (PAM)
	* [http://web.archive.org/web/20030406235542/http://homepage.ntlworld.com:80/quantium/ahr/pcm.htm A page on PCM history] (Archived as of April 6, 2003)		* [http://web.archive.org/web/20030406235542/http://homepage.ntlworld.com:80/quantium/ahr/pcm.htm A page on PCM history] (Archived as of April 6, 2003)
			<references/>
			{{navbox audio codecs}}
	[[Category:Technical]]		[[Category:Technical]]

Porcuswiki: A "decode" --> "encode"

2022-01-18T17:12:20Z

A "decode" --> "encode"

← Older revision		Revision as of 17:12, 18 January 2022
Line 14:		Line 14:

	=== Differential PCM ===		=== Differential PCM ===
	''Differential'' PCM will, in simplified terms, ~~decode~~ the difference between consecutive samples. The ''adaptive differential PCM'' ([[ADPCM]]) variant is common in e.g. telecommunication, where the signal is typically companded using given nonlinear functions specified as A-law<ref>https://en.wikipedia.org/wiki/A-law_algorithm</ref> and µ-law<ref>https://en.wikipedia.org/wiki/%CE%9C-law_algorithm</ref> (wikipedia links).		''Differential'' PCM will, in simplified terms, encode the difference between consecutive samples. The ''adaptive differential PCM'' ([[ADPCM]]) variant is common in e.g. telecommunication, where the signal is typically companded using given nonlinear functions specified as A-law<ref>https://en.wikipedia.org/wiki/A-law_algorithm</ref> and µ-law<ref>https://en.wikipedia.org/wiki/%CE%9C-law_algorithm</ref> (wikipedia links).

Porcuswiki: Linkification; and removed DAT (who cares anymore?); audio over HDMI ...

2022-01-12T09:10:10Z

Linkification; and removed DAT (who cares anymore?); audio over HDMI ...

← Older revision		Revision as of 09:10, 12 January 2022
Line 3:		Line 3:
	'''Pulse Code Modulation''' ('''PCM''') is a method of recording sound as digital data. For more information on the method, its history and uses, see the Wikipedia entry.<ref>https://en.wikipedia.org/wiki/PCM</ref>		'''Pulse Code Modulation''' ('''PCM''') is a method of recording sound as digital data. For more information on the method, its history and uses, see the Wikipedia entry.<ref>https://en.wikipedia.org/wiki/PCM</ref>

	(Linear) PCM is used ~~in the~~ [[CD]] ~~and [[DAT]] formats~~, can ~~also~~ be found on [[DVD]] and [[Blu-Ray]] discs, is the data form transmitted in AES3 / S/PDIF digital audio interfaces, <ref>https://en.wikipedia.org/wiki/AES3#Protocol</ref> and is the most common content of [[RIFF WAVE\|WAVE]] and [[Audio Interchange File Format\|AIFF]] files. Most [[lossless]] audio [[codecs]] for end-users compress linear PCM. Being by far the most common form for audio end-users, one will often see linear PCM referred to as merely "PCM". The phrases "linear PCM" or the abbreviation "LPCM" occur more common in the context of [[DVD]] or Blu-Ray<ref>See for example https://en.wikipedia.org/wiki/Blu-ray#Audio for this usage</ref>, sometimes leading to the erroneous notion that "linear PCM" necessarily must be of the form supported by the DVD formats.		(Linear) PCM is used for audio [[CD]], can (optionally) be found on [[DVD]] (and [[Blu-Ray]]) discs, is the data form transmitted in AES3 / S/PDIF digital audio interfaces<ref>https://en.wikipedia.org/wiki/AES3#Protocol</ref> and is the most common content of [[RIFF WAVE\|WAVE]] and [[Audio Interchange File Format\|AIFF]] files. Most [[lossless]] audio [[codec\|codecs]] for end-users compress linear PCM. Being by far the most common form for audio end-users, one will often see linear PCM referred to as merely "PCM". The phrases "linear PCM" or the abbreviation "LPCM" occur more common in the context of DVD or Blu-Ray<ref>See for example https://en.wikipedia.org/wiki/Blu-ray#Audio for this usage</ref>, sometimes leading to the erroneous notion that "linear PCM" necessarily must be of the form supported by the DVD formats.

	[[ADPCM]] is common in telecommunication.		[[ADPCM]] is common in telecommunication.
Line 9:		Line 9:

	=== Linear PCM ===		=== Linear PCM ===
	In ''Linear'' PCM, the quantization levels are linear in amplitude. To visualize, each 16-bit sample of CD audio represents the amplitude as a number between −32768 and 32767 in ''equidistant'' steps: a difference from 2 to 11 makes for the same as the difference from 13000 to 13009. Linear PCM can be converted with ordinary multi-bit converters: the 12th bit contributes the same to the analog signal no matter what the other bits are.		In ''Linear'' PCM, the quantization levels are linear in amplitude. To visualize, each 16-bit sample of CD audio represents the amplitude as a number between −32768 and 32767 in ''equidistant'' steps: a difference from 2 to 11 makes for the same as the difference from 13000 to 13009. Linear PCM can be converted with ordinary multi-bit converters: the 12th bit contributes the same to the analog signal no matter what the other bits are. Consumer-audio "digital output" connections like S/PDIF (coaxial or TOSlink optical, the latter more common from computer motherboards) and audio over HDMI (although other encodings might be transferred as well).

	As a counterexample formed by modifying a PCM signal with a nonlinearity: [[High_Definition_Compatible_Digital\|HDCD]]'s low level adjustment can flag the lower bits to signify something else if the signal is close to zero (i.e., depending on the more significant bits), and its peak extension is also a nonlinearity. A non-HDCD-aware DAC will omit these steps, and decode linearly.		As a counterexample formed by modifying a PCM signal with a nonlinearity: [[High_Definition_Compatible_Digital\|HDCD]]'s low level adjustment can flag the lower bits to signify something else if the signal is close to zero (i.e., depending on the more significant bits), and its peak extension is also a nonlinearity. A non-HDCD-aware DAC will omit these steps, and decode linearly - the DAC will receive as 'PCM', as the flags are hidden in the signal.

	=== Differential PCM ===		=== Differential PCM ===
Line 24:		Line 24:
	* [[Pulse-Density Modulation]] (PDM)		* [[Pulse-Density Modulation]] (PDM)
	* [[Pulse-Amplitude Modulation]] (PAM)		* [[Pulse-Amplitude Modulation]] (PAM)

	* [http://web.archive.org/web/20030406235542/http://homepage.ntlworld.com:80/quantium/ahr/pcm.htm A page on PCM history] (Archived as of April 6, 2003)		* [http://web.archive.org/web/20030406235542/http://homepage.ntlworld.com:80/quantium/ahr/pcm.htm A page on PCM history] (Archived as of April 6, 2003)


	[[Category:Technical]]		[[Category:Technical]]

Porcuswiki: General rewrite.

2022-01-07T23:54:22Z

General rewrite.

← Older revision		Revision as of 23:54, 7 January 2022
Line 1:		Line 1:
	{{stub}}		{{stub}}

	'''Pulse Code Modulation''' ('''PCM''') is a method of recording sound as digital data. ~~The amplitude of~~ the ~~audio signal is sampled at a regular [[sampling rate]]~~, and ~~[[Quantization\|quantized]] with a fixed [[bit depth]]~~.		'''Pulse Code Modulation''' ('''PCM''') is a method of recording sound as digital data. For more information on the method, its history and uses, see the Wikipedia entry.<ref>https://en.wikipedia.org/wiki/PCM</ref>

	~~This technology was created~~ by ~~Alec Reeves~~ in ~~1937~~.		(Linear) PCM is used in the [[CD]] and [[DAT]] formats, can also be found on [[DVD]] and [[Blu-Ray]] discs, is the data form transmitted in AES3 / S/PDIF digital audio interfaces, <ref>https://en.wikipedia.org/wiki/AES3#Protocol</ref> and is the most common content of [[RIFF WAVE\|WAVE]] and [[Audio Interchange File Format\|AIFF]] files. Most [[lossless]] audio [[codecs]] for end-users compress linear PCM. Being by far the most common form for audio end-users, one will often see linear PCM referred to as merely "PCM". The phrases "linear PCM" or the abbreviation "LPCM" occur more common in the context of [[DVD]] or Blu-Ray<ref>See for example https://en.wikipedia.org/wiki/Blu-ray#Audio for this usage</ref>, sometimes leading to the erroneous notion that "linear PCM" necessarily must be of the form supported by the DVD formats.

			[[ADPCM]] is common in telecommunication.


			=== Linear PCM ===
			In ''Linear'' PCM, the quantization levels are linear in amplitude. To visualize, each 16-bit sample of CD audio represents the amplitude as a number between −32768 and 32767 in ''equidistant'' steps: a difference from 2 to 11 makes for the same as the difference from 13000 to 13009. Linear PCM can be converted with ordinary multi-bit converters: the 12th bit contributes the same to the analog signal no matter what the other bits are.

			As a counterexample formed by modifying a PCM signal with a nonlinearity: [[High_Definition_Compatible_Digital\|HDCD]]'s low level adjustment can flag the lower bits to signify something else if the signal is close to zero (i.e., depending on the more significant bits), and its peak extension is also a nonlinearity. A non-HDCD-aware DAC will omit these steps, and decode linearly.

			=== Differential PCM ===
			''Differential'' PCM will, in simplified terms, decode the difference between consecutive samples. The ''adaptive differential PCM'' ([[ADPCM]]) variant is common in e.g. telecommunication, where the signal is typically companded using given nonlinear functions specified as A-law<ref>https://en.wikipedia.org/wiki/A-law_algorithm</ref> and µ-law<ref>https://en.wikipedia.org/wiki/%CE%9C-law_algorithm</ref> (wikipedia links).


			== References ==
			<references/>

	== See also ==		== See also ==

	* [[Pulse-Density Modulation]] (PDM)		* [[Pulse-Density Modulation]] (PDM)
	* [[Pulse-Amplitude Modulation]] (PAM)		* [[Pulse-Amplitude Modulation]] (PAM)

68.50.20.20: /* See also */ archiveurl for history link

2020-09-16T04:17:58Z

Speckmade at 14:34, 14 June 2007

2007-06-14T14:34:17Z

← Older revision		Revision as of 14:34, 14 June 2007
Line 5:		Line 5:
	This technology was created by Alec Reeves in 1937.		This technology was created by Alec Reeves in 1937.

	==See also==		== See also ==
	* [[~~PDM~~]]		* [[Pulse-Density Modulation]] (PDM)
	* [[~~PAM~~]]		* [[Pulse-Amplitude Modulation]] (PAM)

	* [http://homepage.ntlworld.com/quantium/ahr/pcm.htm A page on PCM history]		* [http://homepage.ntlworld.com/quantium/ahr/pcm.htm A page on PCM history]




	[[Category:Technical]]		[[Category:Technical]]

Speckmade: PCM moved to Pulse Code Modulation

2007-06-13T16:50:50Z

PCM moved to Pulse Code Modulation

← Older revision	Revision as of 16:50, 13 June 2007
(No difference)

Pepoluan: {{stub}} to top

2006-09-08T18:46:11Z

{{stub}} to top

← Older revision		Revision as of 18:46, 8 September 2006
Line 1:		Line 1:
			{{stub}}

	'''Pulse Code Modulation''' ('''PCM''') is a method of recording sound as digital data. The amplitude of the audio signal is sampled at a regular [[sampling rate]], and [[Quantization\|quantized]] with a fixed [[bit depth]].		'''Pulse Code Modulation''' ('''PCM''') is a method of recording sound as digital data. The amplitude of the audio signal is sampled at a regular [[sampling rate]], and [[Quantization\|quantized]] with a fixed [[bit depth]].

Line 9:		Line 11:


	~~{{stub}}~~


	[[Category:Technical]]		[[Category:Technical]]

Pepoluan at 08:11, 2 September 2006

2006-09-02T08:11:03Z

← Older revision		Revision as of 08:11, 2 September 2006
Line 3:		Line 3:
	This technology was created by Alec Reeves in 1937.		This technology was created by Alec Reeves in 1937.

	See also: [[PDM]] ~~and~~ [[PAM]]		==See also==
			* [[PDM]]
			* [[PAM]]
			* [http://homepage.ntlworld.com/quantium/ahr/pcm.htm A page on PCM history]

	~~[http://homepage.ntlworld.com/quantium/ahr/pcm.htm A page on PCM history]~~

			{{stub}}

	~~{{stub}}~~
			[[Category:Technical]]

Rjamorim at 16:03, 4 July 2005

2005-07-04T16:03:22Z

← Older revision		Revision as of 16:03, 4 July 2005
Line 1:		Line 1:
	'''Pulse Code Modulation''' ('''PCM''') is a method of recording sound as digital data. The amplitude of the audio signal is sampled at a regular [[sampling ~~frequency~~]], and [[Quantization\|quantized]] with a fixed [[bit depth]].		'''Pulse Code Modulation''' ('''PCM''') is a method of recording sound as digital data. The amplitude of the audio signal is sampled at a regular [[sampling rate]], and [[Quantization\|quantized]] with a fixed [[bit depth]].

	This technology was created by Alec Reeves in 1937.		This technology was created by Alec Reeves in 1937.

← Older revision		Revision as of 04:17, 16 September 2020
Line 9:		Line 9:
	* [[Pulse-Amplitude Modulation]] (PAM)		* [[Pulse-Amplitude Modulation]] (PAM)

	* [http://homepage.ntlworld.com/quantium/ahr/pcm.htm A page on PCM history]		* [http://web.archive.org/web/20030406235542/http://homepage.ntlworld.com:80/quantium/ahr/pcm.htm A page on PCM history] (Archived as of April 6, 2003)


	[[Category:Technical]]		[[Category:Technical]]