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We’re in 2016 yet our computers insist on shipping with atrocious default video decoding settings. The first cardinal sin, which is immediately noticeable, is having a 16-235 range instead of 0-255. Blacks become grey, and pure white is slightly dim.

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BT.601 is a standard from 1982 which, among other things, defines how RGB color primaries get turned into the YCbCr channels used by modern codecs. BT.709 is a standard from 1990 which does the same thing, but the transfer coefficients are slightly different. And unlike its older counterpart, it was not thought of with standard definition in mind, but HD television.

Here’s the problem: a lot of consumer-grade software is either not aware of the difference between the two, or encodes and/or decodes with the wrong one. There are also assumptions being made; video tends to be decoded as 709 if it’s above 720 pixels in height, and 601 if below, regardless of the coefficients it was actually originally encoded with.

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Anyway, generally speaking:

  • Red too orange, green too dark? 601 is being decoded as 709.
  • Red too dark, green too yellowish? 709 is being decoded as 601.

What can you do about this?

Figure a way for your video pipeline to properly handle both.

Adobe Media Encoder may not be as bitrate-efficient as your run-of-the-mill x264+GUI combo, but it does all the righti things and writes all the right metadata to make a fully compliant file. And I would argue in this day and age, when you’re encoding to send a file to YouTube, it doesn’t really matter if you’re picking a less bitrate-efficient encoder because if you care about quality to begin with, you’ll be sending a file as high bitrate as possible (probably reaching above 0.4 bits per pixel).

In fact, I just double-checked as I was writing this post: Adobe Media Encoder is the only software I know of which actually encodes video with its proper YCbCR transfer coefficients.

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Lebled, M. (2016, August 02). BT.601 vs BT.709. Retrieved from http://blog.maxofs2d.net/post/148346073513/bt601-vs-bt709

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