Charles Poynton
-Video engineering
Charles Poynton
-
Here you will find information concerning technical
aspects of video. You might also be interested in my book, Digital
Video and HDTV Algorithms and Interfaces.
If this page is too technical for you, see my Consumer Video page.
To learn how to adjust those pesky controls
on the front of your computer monitor, consult my document describing the
"Brightness"
and "Contrast" controls.
Video systems convey image data in the form of one component that represents lightness (luma), and two components that represent color, disregarding lightness (chroma). The chroma components can be reduced by subsampling (filtering, or averaging). Subsampling is designated by a string of three (or sometimes four) small integers separated by colons, such as 4:2:2. This document gives an overview of subsampling, and explains subsampling notation.
Acrobat PDF format, 167194 bytes
The notation YUV, and the term luminance, are widespread in digital video. However, digital video almost never uses Y'UV color difference components, and never directly represents the luminance of color science. The common terms are almost always wrong. This note explains why. I urge video engineers and computer graphics specialists to use the correct terms, almost always Y'CBCR and luma
Acrobat PDF format, 54864 bytes
In this "white paper" that I wrote for Discreet Logic, I explain the R'G'B' and Y'CBCR 4:2:2 representations, and explain the technical aspects of conversion between the two. I conclude by suggesting steps that can be taken during production and post-production to avoid difficulty with the conversion.
On February 6, 1998, I presented a paper, Luminance, luma, and the migration to DTV, at the 32nd SMPTE Advanced Motion Imaging Conference in Toronto. For now, just the abstract is available. The technical note Errors due to nonconstant luminance contains information on this topic. I am in the proces of preparing a published version of the paper. Some information concerning the Principle of Constant Luminance is available in this IS&T paper ...
I presented this paper at the SPIE/IS&T Conference in San Jose, Calif., Jan. 26 - 30, 1998. The paper is published in the Proceedings of that conference, B. E. Rogowitz and T. N. Pappas (eds.), Proceedings of SPIE 3299, 232-249 (Bellingham, Wash.: SPIE, 1998).
I presented this paper at the SMPTE conference in Seattle, February 1-3, 1996; it is published in The convergence continues ... Computer technology and television: Proceedings of the 30th SMPTE Advanced motion imaging conference, 192-202 (White Plains, New York: SMPTE, 1996).
International Broadcasting Symposium '95, Broadcasting in the Multimedia Age, Tokyo, Japan, Nov. 1995.
This article describes the theory of color reproduction in video, and some of the engineering compromises necessary to make practical cameras and practical coding systems. I presented this paper at the SMPTE Advanced Television and Electronic Imaging Conference, San Francisco, Feb. 1995. This is an edited version of the paper published in the proceedings of that conference, New Foundations for Video Technology (pages 167-180).
International Technical Workshop on Multimedia Technologies in the HDTV Age, IEEE CES Tokyo Chapter, July 20, 1993.
132nd SMPTE Technical Conference, New York, October
13-17, 1990.
Technical information about gamma and color, including details of video coding.
A few short technical articles are available:
I rummaged around the attic and came up with a handful of short articles that I have written on diverse subjects. All are in ASCII text format; most are less than 10 KB. Most are copies or direct adaptations of Usenet news postings.