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== Effect ==
Although DSC is not mathematically [[Lossless compression|lossless]], it meets the ISO/IEC 29170 standard for "[[visually lossless]]" compression, a form of compression in which "the user cannot tell the difference between a compressed and uncompressed image".<ref>{{cite journal |last1=Walls |first1=Frederick |last2=MacInnis |first2=Alexander Sandy |title=27.4L: Late-News Paper : VESA Display Stream Compression: An Overview |journal=SID Symposium Digest of Technical Papers |date=June 2014 |volume=45 |issue=1 |pages=360–363 |doi=10.1002/j.2168-0159.2014.tb00097.x}}</ref> ISO 29170 more specifically defines an algorithm as visually lossless "when all the observers fail to correctly identify the reference image more than 75% of the trials".<ref name=ISO29170>{{cite web |title=ISO/IEC 29170-2:2015 — Information technology — Advanced image coding and evaluation — Part 2: Evaluation procedure for nearly lossless coding |url=https://www.iso.org/standard/66094.html |website=iso.org |publisher=[[ISO|International Organization for Standardization (ISO)]] |ref=ISO29170 |___location=Geneva, Switzerland |format=PDF |date=August 2015}}</ref>{{rp|18}} However, the standard allows for images that "exhibit particularly strong artifacts" to be disregarded or excluded from testing, such as engineered test images.<ref name=ISO29170 />{{rp|13,18}} Research of DSC using the ISO/IEC 29170 interleaved protocol, in which an uncompressed reference image is presented side by side with a rapidly alternating sequence of the compressed test image and uncompressed reference image,<ref name=ISO29170 />{{rp|10}} and performed with various types of images (such as people, natural and man-made scenery, text, and known challenging imagery) shows that in most images DSC satisfies the standard's criterion for visually lossless performance, although in some trials participants were able to detect the presence of compression on certain images.<ref name="Sudhama">{{cite journal |last1=Sudhama |first1=Aishwarya |last2=Cutone |first2=Matthew |last3=Hou |first3=Yuqian |last4=Goel |first4=James |last5=Dale |first5=Stolitzka |last6=Jacobson |first6=Natan |last7=Allison |first7=Robert |last8=Wilcox |first8=Laurie |title=Visually Lossless Compression of High Dynamic Range Images: A Large-Scale Evaluation |journal=SID Symposium Digest of Technical Papers |date=May 2018 |volume=49 |issue=1 |pages=1151–1154 |doi=10.1002/sdtp.12106 |url=https://static1.squarespace.com/static/565e05cee4b01c87068e7984/t/6000baf6782fa205430dc4b6/1610660599845/Sudhama_Allison_Wilcox_2018SID.pdf |access-date=4 March 2021}}</ref><ref name="Mohona">{{cite book |last1=Mohona |first1=Sanjida |last2=Au |first2=Domenic |last3=Kio |first3=Onoise |last4=Robinson |first4=Richard |last5=Hou |first5=Yuqian |last6=Wilcox |first6=Laurie |last7=Allison |first7=Robert |title=2020 Twelfth International Conference on Quality of Multimedia Experience (QoMEX) |chapter=Subjective Assessment of Stereoscopic Image Quality: The Impact of Visually Lossless Compression |date=May 2020 |pages=1–6 |doi=10.1109/QoMEX48832.2020.9123129
== Algorithm ==
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DSC version 1.0 was released on 10 March 2014, but was soon deprecated by DSC version 1.1 released on 1 August 2014. The DSC standard supports up to a {{ratio|3:1}} compression ratio (reducing the data stream to 8 bits per pixel) with constant or variable bit rate, RGB or [[YCbCr|{{YCbCr}}]] [[chroma subsampling|4:4:4]], 4:2:2, or 4:2:0 color format, and color depth of 6, 8, 10, or 12 bits per color component.
DSC version 1.2 was released on 27 January 2016 and is included in version 1.4 of the DisplayPort standard; DSC '''version 1.2a''' was released on 18 January 2017.<ref>https://app.box.com/s/vcocw3z73ta09txiskj7cnk6289j356b/file/203635076004</ref> The update includes native encoding of 4:2:2 and 4:2:0 formats in six-pixel containers, 14/16 bits per color, and minor modifications to the encoding algorithm. The specification for DSC '''version 1.2b''' was published on 12 August 2021,<ref>https://app.box.com/s/vcocw3z73ta09txiskj7cnk6289j356b/file/847125003356</ref> with [[VESA]]'s website claiming that DisplayPort 1.4a was the first iteration to take advantage of the new version.<ref>https://vesa.org/vesa-display-compression-codecs/dsc/</ref> However, conflicting information on the DisplayPort website claims 1.2a is still the newest version.<ref>https://www.displayport.org/faq/#tab-display-stream-compression-dsc</ref>
On 4 January 2017, [[HDMI 2.1]] was announced which supports up to [[10K resolution]] and uses DSC 1.2 for video that is higher than 8K resolution with 4:2:0 [[chroma subsampling]].<ref name=HDMI21PressRelease>{{cite news |url=http://www.hdmi.org/press/press_release.aspx?prid=145 |title=HDMI Forum announces version 2.1 of the HDMI specification |publisher=HDMI.org |date=2017-01-04 |access-date=2017-01-10 |archive-date=2017-01-08 |archive-url=https://web.archive.org/web/20170108081018/http://www.hdmi.org/press/press_release.aspx?prid=145 |url-status=dead }}</ref><ref name=HDMI21Introduction>{{cite news |url=http://www.hdmi.org/manufacturer/hdmi_2_1/index.aspx |title=Introducing HDMI 2.1 |publisher=HDMI.org |access-date=2017-01-10 |archive-date=6 January 2017 |archive-url=https://web.archive.org/web/20170106195344/http://www.hdmi.org/manufacturer/hdmi_2_1/index.aspx |url-status=dead }}</ref><ref name=HDMI21January2017Anandtech>{{cite news |url=http://www.anandtech.com/show/11003/hdmi-21-announced-8kp60-48gbps-cable |archive-url=https://web.archive.org/web/20170106100230/http://www.anandtech.com/show/11003/hdmi-21-announced-8kp60-48gbps-cable |url-status=dead |archive-date=January 6, 2017 |title=HDMI 2.1 Announced|author=Anton Shilov |publisher=Anandtech |date=2017-01-05 |access-date=2017-01-10}}</ref>
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