Transcoding: Difference between revisions

Revision as of 14:36, 12 June 2022

Revision as of 09:16, 22 June 2022

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{{Short description|Direct digital-to-digital conversion of one encoding to another}}

{{Other uses|Transcode (disambiguation)|H.264/MPEG-4 AVC products and implementations#Transcoding}}

{{refimproveRefimprove|date=October 2015}}

'''Transcoding''' is the direct digital-to-digital conversion of one [[data compression|encoding]] to another,<ref>{{cite web|author1=Margaret Rouse|title=transcoding|url=http://searchmicroservices.techtarget.com/definition/transcoding}}</ref> such as for [[movie]] data files, audio files (e.g., [[MP3]], [[WAV]]), or [[character encoding]] (e.g., [[UTF-8]], [[ISO/IEC 8859]]). This is usually done in cases where a target device (or [[workflow]]) does not support the format or has limited storage capacity that mandates a reduced file size,<ref name="SMP">

"Advancements in Compression and Transcoding: 2008 and Beyond",

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==Re-encoding/recoding ==

One may also '''re-encode''' data in the same format, for a number of reasons:

;Editing: If one wishes to edit data in a compressed format (for instance, perform image editing on a [[JPEG]] image), one will generally decode it, edit it, then re-encode it. This re-encoding causes [[digital generation loss]]; thus if one wishes to edit a file repeatedly, one should only decode it ''once,'' and make all edits on that copy, rather than repeatedly re-encoding it. Similarly, if encoding to a lossy format is required, it should be deferred until the data is finalised, e.g. after mastering.

; Editing

;Lower bitrate: '''[[Transrating]]''' is a process similar to transcoding in which files are coded to a lower bitrate without changing video formats;<ref name="Ryan">{{cite web|last1=Branson|first1=Ryan (6 July 2015)|title=Why is Bit Rate Important When Converting Videos to MP3?|url=http://converta2z.blogspot.in/2015/07/why-is-bit-rate-important-when.html|website=Online Video Converter|date=6 July 2015|access-date=10 August 2015}}</ref> this can include [[sample rate conversion]], but may use an identical sampling rate with higher compression. This allows one to fit given media into smaller storage space (for instance, fitting a [[DVD]] onto a [[Video CD]]), or over a lower bandwidth channel.

;Editing: If one wishes to edit data in a compressed format (for instance, perform image editing on a [[JPEG]] image), one will generally decode it, edit it, then re-encode it. This re-encoding causes [[digital generation loss]]; thus if one wishes to edit a file repeatedly, one should only decode it ''once,'', and make all edits on that copy, rather than repeatedly re-encoding it. Similarly, if encoding to a lossy format is required, it should be deferred until the data is finalised, e.g. after mastering.

;[[Image scaling]]: Changing the picture size of video is known as '''transsizing''', and is used if the output resolution differs from the resolution of the media. On a powerful enough device, image scaling can be done on playback, but it can also be done by re-encoding, particularly as part of transrating (such as a [[Downsampling|downsampled]] image requiring a lower bitrate).

; Lower bitrate

;Lower bitrate: '''[[Transrating]]''' is a process similar to transcoding in which files are coded to a lower bitrate without changing video formats;<ref name="Ryan">{{cite web|last1=Branson|first1=Ryan (6 July 2015)|title=Why is Bit Rate Important When Converting Videos to MP3?|url=http://converta2z.blogspot.in/2015/07/why-is-bit-rate-important-when.html|website=Online Video Converter|date=6 July 2015|access-date=10 August 2015}}</ref> this can include [[sample rate conversion]], but may use an identical sampling rate with higher compression. This allows one to fit given media into smaller storage space (for instance, fitting a [[DVD]] onto a [[Video CD]]), or over a lower bandwidth channel.

; [[Image scaling]]

;[[Image scaling]]: Changing the picture size of video is known as '''transsizing''', and is used if the output resolution differs from the resolution of the media. On a powerful enough device, image scaling can be done on playback, but it can also be done by re-encoding, particularly as part of transrating (such as a [[Downsampling|downsampled]] image requiring a lower bitrate).

One can also use formats with [[bitrate peeling]], that allow one to easily lower the bitrate without re-encoding, but quality is often lower than a re-encode. For example, in [[Vorbis]] bitrate peeling as of 2008, the quality is inferior to re-encoding.

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==See also==

; Concepts

* [[Data conversion]]

* [[Data transformation]]

* [[Lossy data conversion]]

* Data transformation

* [[Type conversion]]

* [[Video coding]]

; Comparison

* [[Comparison of video converters]]

* [[Comparison of DVD ripper software]]

* [[Comparison of video converters]]

==Notes Citations ==

{{reflistReflist}}

== General and cited references ==

==References==

* [[Federal Standard 1037C]]

* [[MIL-STD-188]]

* [[List of Portable Multimedia Software]]

* P. A. A. Assuncao and M. Ghanbari, "[https://ieeexplore.ieee.org/document/736724 A frequency-___domain video transcoder for dynamic bit-rate reduction of MPEG-2 bit streams],", in ''IEEE Transactions on Circuits and Systems for Video Technology'', vol. 8, no. 8, pp. 953-967, Dec. 1998.

* Huifang Sun, Xuemin Chen, and Tihao Chiang, ''[https://www.routledge.com/Digital-Video-Transcoding-for-Transmission-and-Storage/Sun-Chiang-Chen/p/book/9780849316944 Digital Video Transcoding for Transmission and Storage]'', New York, CRC Press, 2005.

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{{Authority control}}

[[Category:Video conversion software]]

[[Category:Audio format converters| ]]

[[Category:Film and video technology]]

[[Category:Video conversion software]]