Preface
Video technology continues to advance since the publication, in early 2003, of the first edition of this book. Further “convergence” – Jim Blinn might say collision – between video and computer graphics has occurred. Television is losing; computing and internet transport are winning. Even the acronym “TV” is questionable today: Owing to its usage over the last half century, TV implies broadcast, but much of today’s video – from the Apple iTunes store, Hulu, NetFlix, YouTube – is not broadcast in the conventional sense. In this edition,
I have replaced SDTV with SD and HDTV with HD. Digital video is now ubiquitous; analog scanning, as
depicted by Figure P.1 below, is archaic. In this edition, I promote the pixel array to first-class status. The first edition described scan lines; I have retrained myself to speak of image rows and image columns instead.
I expunge microseconds in favour of sample counts;
I expunge millivolts in favour of pixel values. Phrases in the previous edition such as “immense data capacity” have been replaced by “fairly large” or even “modest data capacity.”
Figure P.1 Scanning a raster, as suggested by this sketch, is obsolete. In modern video and HD, the image exists in a pixel array. Any book that describes image acquisition or display using a drawing such as this doesn’t accurately portray digital video.
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Many chapters here end with
a Further reading section if extensive, authoritative information on the chapter’s topic is available elsewhere.
In my first book Technical Introduction to Digital Video, published in 1996, and in the first edition of the present book, I described encoding and then decoding. That order made sense to me from an engineering perspective. However, I now think it buries a deep philosophical flaw. Once program material is prepared, decoded, and viewed on a reference display in the studio, and mastered – that is, downstream of final approval – only the decoding and display matters. It is convenient for image data to be captured and encoded in a manner that displays a realistic image at review, but decoding and presentation of the image data at mastering is preeminent. If creative staff warp the colours at encoding in order to achieve an æsthetic effect – say they lift the black levels by 0.15, or rotate hue by 123° – the classic encoding equations no longer apply, but those image data modifications are not evidence of faulty encoding, they are consequence of the exercise of creative intent. The traditional explanation is presented in a manner that suggests that the encoding is fixed; however, what really matters is that decoding is fixed. The principle that I’m advocating is much like the principle of MPEG, where the decoder is defined precisely but the encoder is permitted to do anything that produces a legal bitstream. In this edition I emphasize decoding. A new chapter – Chapter 2, on page 19 – outlines this philosophy.
Video technology is a broad area. There are entire books that cover subject matter for which this book provides only a chapter. My expertise centres on image coding aspects, particularly the relationship between vision science, colour science, image science, signal processing, and video technology. Chapters of this book on those topics – mainly, the topics of the Theory part of this book – have (as far as I know) no textbook counterpart.
Legacy technology
SMPTE is the source of many standards, both legacy and modern. During the interval between the first and second editions of this book, SMPTE abolished the M suffix of many historical standards, and prepended ST to standards (paralleling EG for Engineering Guideline and
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www.poynton.com/CNPLVS/
I designed this book with wide margins. I write notes here, and I encourage you to do the same!
Bringhurst, Robert (2008), The Elements of Typographic Style, version/edition 3.1, (Vancouver, B.C.: Hartley & Marks).
Tschichold, Jan (1991), The Form of the Book (London: Lund Humphries). [Originally published in German in 1975.]
Tufte, Edward R. (1990), Envisioning Information (Cheshire, Conn.: Graphic Press).
RP for Recommended Practice). I cite recent SMPTE standards according to the new nomenclature.
As of 2012, we can safely say that analog television technology and composite (NTSC/PAL) television technology are obsolete. When writing the first edition of this book, I concentrated my efforts on the things that I didn’t expect to change rapidly; nonetheless, perhaps 15 or 20 percent of the material in the first edition represents technology – mainly analog and composite and NTSC and PAL – that we would now classify as “legacy.” It is difficult for an author to abandon work that he or she has written that represents hundreds or thousands of hours of work; nonetheless, I have removed this material and placed it in a self-contained book entitled Composite NTSC and PAL: Legacy Video Systems that is freely available on the web.
Layout and typography
Many years ago, when my daughter Quinn was proofreading a draft chapter of the first edition of this book, she circled, in red, two lines at the top of a page that were followed by a new section. She drew an arrow indicating that the two lines should be moved to the bottom of the previous page. She didn’t immediately realize that the lines had wrapped to the top of the page because there was no room for them earlier. She marked them nonetheless, and explained to me that they needed to be moved because that section should start at the top of the page. Quinn intuitively understood the awkward page break – and she was only twelve years old! I have spent a lot of time executing the illustration, layout, and typesetting for this book, based upon my belief that this story is told not only through the words but also through pictures and layout.
In designing and typesetting, I continue to be inspired by the work of Robert Bringhurst, Jan Tschichold, and Edward R. Tufte; their books are cited in the margin.
Formulas
It is said that every formula in a book cuts the potential readership in half. I hope readers of this book can compute that after a mere ten formulas my readership would drop to 2-10! I decided to retain formulas, but
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they are not generally necessary to achieve an understanding of the concepts. If you are intimidated by
a formula, just skip it and come back later if you wish. I hope that you will treat the mathematics the way that Bringhurst recommends that you treat his mathematical description of the principles of page composition. In Chapter 8 of his classic book, Elements of Typographic Style, Bringhurst says,
“The mathematics are not here to impose drudgery upon anyone. On the contrary, they are here entirely for pleasure. They are here for the pleasure of those who like to examine what they are doing, or what they might do or have already done, perhaps in the hope of doing it still better. Those who prefer to act directly at all times, and leave the analysis to others, may be content in this chapter to study the pictures and skim the text.”
Spelling
At the urging of my wife Barbara and my two daughters, I have resumed spelling colour with a u. However, colorimetric and colorimetry are without. Greyscale is now spelled with an e (for English), not with an a (for American). The world is getting smaller, and Google’s reach is worldwide; however, cultural diversity shouldn’t suffer.
I tried carefully to avoid errors while preparing this book. Nonetheless, despite my efforts and the efforts of my reviewers, a few errors may have crept in. As with
www.poynton.com/DVAI2/ my previous book, I will compile errata for this book and make the corrections available at the URL indicated in the margin. Please report any error that you discover, and I will endeavour to repair it and attribute the correction to you!
Charles Poynton
Toronto, Jan. 2012
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