GlossaryRec. 709

Rec. 709

Rec. 709 (ITU-R BT.709) is the international standard that defines the color space, brightness curve and other picture settings for HD video. Rec. 709 is the default for most standard dynamic range (SDR) content on the web, TV and streaming services. Its color range covers less than Rec. 2020, which is used for HDR. Most displays and players assume Rec. 709 when no other metadata is present.

Why it matters

Rec. 709 is the safe common ground for video delivery. Content in Rec. 709 looks right on almost every phone, laptop and TV. Platforms that receive HDR or wide color uploads usually need a Rec. 709 version as well, or many viewers will see wrong colors.

How it works

  1. Rec. 709 defines which red, green and blue primaries make up the color range.
  2. It sets the brightness curve (gamma) used to store light levels in the file.
  3. It defines how RGB converts to YCbCr and the frame sizes and rates for HD.
  4. Files are tagged as Rec. 709 so players display them with matching settings.

Should I export video in Rec. 709?

Yes, for standard dynamic range video meant for the web, social and streaming, export in Rec. 709. It is what most players assume when no color tags are present, and YouTube recommends it for SDR uploads. Only use Rec. 2020 when you are delivering HDR.

Rec. 709 vs sRGB: are they the same?

They share the same color primaries, so the range of colors is identical. They differ in the brightness curve: sRGB is designed for computer screens in brighter rooms, while Rec. 709 targets video viewing. In practice, Rec. 709 video looks close to correct on sRGB monitors.

Where it's used

Video platforms, OTT services and short video apps deliver most standard video in Rec. 709, because nearly every screen shows it correctly. HDR uploads are converted to it for older devices.

By the numbers

  • The first official version of Rec. 709 was approved by the CCIR in 1990, and the current version, BT.709-6, was released in June 2015. (Wikipedia: Rec. 709)
  • Rec. 709 specifies a 1920 by 1080 image with 8-bit or 10-bit encoding. (Wikipedia: Rec. 709)

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