Editing DV (video format) (section)

== Compression ==
DV uses [[lossy compression]] of [[video]] while audio is stored uncompressed.<ref>{{cite web |title=DV Q&A Our Expert Answers Your Questions |url=http://www.videomaker.com/article/7330 |work=Videomaker magazine |publisher=Videomaker |date=October 1999 }}</ref> An [[intraframe]] [[video compression]] scheme is used to compress video on a frame-by-frame basis with the [[discrete cosine transform]] (DCT).

Closely following the [[ITU-R]] [[Rec. 601]] standard, DV video employs [[interlaced video|interlaced]] scanning with the luminance sampling frequency of 13.5&nbsp;MHz. This results in 480 scanlines per complete frame for the 60&nbsp;Hz system, and 576 scanlines per complete frame for the 50&nbsp;Hz system. In both systems the active area contains 720 pixels per scanline, with 704 pixels used for content and 16 pixels on the sides left for digital blanking. The same frame size is used for 4:3 and 16:9 frame aspect ratios, resulting in different [[pixel aspect ratio]]s for ''fullscreen'' and ''widescreen'' video.<ref name="DVCAM_OVERVIEW">{{cite web |url=http://www.sony.ca/dvcam/pdfs/dvcam%20format%20overview.pdf |title=DVCAM Format Overview |archive-url=https://web.archive.org/web/20110928040838/http://www.sony.ca/dvcam/pdfs/dvcam%20format%20overview.pdf |archive-date=28 September 2011 }}</ref><ref>{{cite web |url=http://www.dvmp.co.uk/digital-video.htm |title=Digital Video and Field Order |website=dvmp.co.uk }}</ref>

Prior to the DCT compression stage, [[chroma subsampling]] is applied to the source video in order to reduce the amount of data to be compressed. Baseline DV uses [[Chroma subsampling#4:1:1|4:1:1 subsampling]] in its 60&nbsp;Hz variant and [[Chroma subsampling#4:2:0|4:2:0 subsampling]] in the 50&nbsp;Hz variant. Low chroma resolution of DV (compared to higher-end digital video formats) is a reason this format is sometimes avoided in [[chroma key]]ing applications, though advances in chroma keying techniques and software have made producing quality keys from DV material possible.<ref>{{Cite web |url=http://www.fxguide.com/article314.html|title=fxguide - vfx knowledge - Art of Keying |date=24 March 2006 |archive-url=https://web.archive.org/web/20060324221038/http://www.fxguide.com/article314.html |archive-date=24 March 2006 }}</ref>

Audio can be stored in either of two forms: 16-bit [[Linear PCM]] [[stereophonic sound|stereo]] at 48&nbsp;kHz [[sampling rate]] (768&nbsp;kbit/s per channel, 1.5&nbsp;Mbit/s stereo), or four nonlinear 12-bit PCM channels at 32&nbsp;kHz sampling rate (384&nbsp;kbit/s per channel, 1.5&nbsp;Mbit/s for four channels). In addition, the DV specification also supports 16-bit audio at 44.1&nbsp;kHz (706&nbsp;kbit/s per channel, 1.4&nbsp;Mbit/s stereo), the same sampling rate used for CD audio.<ref name="dvsuccess">{{cite web |last=Puhovski |first=Nenad |date=April 2000 |url=http://www.stanford.edu/~hbreit/CILECT/DV_Report.htm |title=DV – A Success Story |website=Stanford.edu |access-date=26 August 2013 }}</ref> In practice, the 48&nbsp;kHz stereo mode is used almost exclusively.