Talk:YCoCg

Reference template issue

Was the article translated from German without adequate proofreading? The references appear to use {{internetquelle}} which causes the references to be labeled as "in German." However, I just checked reference 3, and it is definitely in English (still need to look at the others). --SoledadKabocha (talk) 00:00, 26 April 2015 (UTC)

Bit efficiency

The YCoCg color model uses the representation of two values as sum and difference. The additional bit needed for Co and Cg (in the lifted version) is also not strictly necessary for encoding, if the most significant bit of the sum and the MSB of the difference is discarded and the MSB of only one of the original values is stored. With this the compression rate can be improved. Sorry, no source. Sebastian --188.195.215.187 (talk) 20:14, 7 December 2019 (UTC)

YCoCg vs YCgCo

This page uniformly uses the "YCoCg" spelling and component ordering while, in practice, the "YCgCo" spelling and ordering are used as well. The page should probably be updated to reflect this.

Examples of codecs using the YCgCo ordering (and spelling) include three of the four codecs mentioned in the introductory paragraph. For reference:

• Advanced Video Coding and High Efficiency Video Coding use YCgCo
  • See the ITU H.264 or ITU H.265 specifications (respectively) equations E34 and E-36
  • For a real implementation, see the FFMPEG source
• JPEG XR uses YCgCo
  • See the ITU T.832 (06/2019) specification, "note 2" towards the bottom of page 172

Examples using the YCoCg ordering (and spelling):

• Dirac (now abandoned, albeit with parts living on in VC-2) uses YCoCg
  • See the Dirac Specification, section F.1.5.2
  • See the Schroedinger Dirac codec source code
• Free Lossless Image Format
  • See source

Another notable use of the YCoCg order is the article "YCoCg-R: A color space with RGB reversibility and low dynamic range", a follow on article by the original authors of the color model in the JVT (I have been unable to find a copy of the original paper online). Of course, the JVT later adopted the YCgCo spelling (and implementation order) in H.264 and H.265) so I don't think it can be claimed that either spelling is authoritative.

Clearly, both YCgCo and YCoCg orders are used by real codecs and therefore both ought to be explicitly mentioned in this article. This is especially important as the two names are frequently used interchangeably in informal use to the point that real software, such as FFMPEG, use one as an alias for the other (for example see FFMPEG). Given this frequent confusion it is important that Wikipedia, given its prominent search rankings, highlight that both orderings are used in practice so care must be taken.

For the record I don't want to start a discussion about which of YCgCo and YCoCg is "most correct" or should be in the page title since this will immediately descend into a tabs-vs-spaces style war.

- - Mossblaser (talk) 12:26, 18 February 2020 (UTC)

AFAIK, both YCgCo and YCoCg are the same, while for example with Dolby vision's IPT and ITP are two color models, where P and T are reversed. 2A00:1FA0:611:5939:75BF:22B5:8686:B116 (talk) 14:04, 5 February 2021 (UTC)

I think the reason for YCoCg is that this is the digital version of YIQ where Co corresponds to I and Cg corresponds to Q. T3h 1337 b0y 08:37, 15 April 2022 (UTC)