Editing Transcoding (section)

==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.
; 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|last=Branson|first=Ryan |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|archive-date=9 August 2015|archive-url=https://web.archive.org/web/20150809101034/http://converta2z.blogspot.in/2015/07/why-is-bit-rate-important-when.html|url-status=live}}</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]]
: 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 [[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.