The pursuit of High Dynamic Range (HDR) is the dream of getting closer to the Human Visual System (HVS) in all that we experience as viewers.
To achieve a balance of getting closer to human perception within the bandwidth limitations of existing infrastructure and technologies, including chroma and luminance sampling, bit depth, and the strengths and weaknesses of Gamma vs Logarithmic curves, a better curve was needed.
Why was a better curve needed and what is the advantage of PQ*?
* PQ is represented in practice by two approaches, HDR10 an open approach and Dolby® Vision, a proprietary system owned by Dolby Laboratories. Both are designed to make the most efficient use of bits throughout the range of luminance and contrast steps possible.
PQ is standardized in SMPTE ST 2084 and BT.2100 and PQ defines a curve that ensures banding is below the Just Noticeable Difference (JND). The PQ curve ensures the most efficient use of code words which minimizes the bit depth required.
For a vivid image, which HDR promises upon delivery to the display, the challenge has been to provide enough useful steps within the color and luminance range to provide smooth gradations and satisfy the viewer. Dolby Vision is a new way of defining how a picture looks on a TV. It is a "display referred" system where each code value defines a specific brightness (i.e. there is no user brightness control). Dolby Vision has a method to send 12-bit data down a HDMI cable utilizing 4096 shades for smooth gradations. For contemporary production pipelines, the challenge is that most pipelines are 10-bit with 1024 shades or steps available. HDR 10, Dolby Vision and HLG have been designed to solve this dilemma by efficiently choosing to utilize curves across the luminance and color ranges that minimize perceptual banding and achieve results that are closer to the human vision system, enabling incredible results.
HDR10 is a Media Profile defined by the Consumer Technologies Association (CTA).
HDR10 uses SMPTE ST-2086 "Mastering Display Color Volume" static metadata to send color calibration data of the mastering display, as well as MaxFALL (Maximum Frame Average Light Level) and MaxCLL (Maximum Content Light Level) static values. HDR10 is an open standard supported by a wide variety of companies.
HDR10+ builds from HDR10*, adding dynamic metadata and more, allowing for scene by scene or even shot by shot variation. The standard allows for recognizing a display's color space and more. Samsung is the primary driver for this evolution of the original standard.
HDR10+ has recently been adopted by a range of companies and resulted in the creation of the HDR10+ Alliance with members comprising Amazon, Samsung, Panasonic, 20th Century Fox, and Warner Bros and more.
HLG (Hybrid Log Gamma) is an HDR approach that was jointly developed by the BBC and NHK. HLG uses relative luminance values and builds on the BT.2020 standard for a wider color gamut and adds PQ and HLG dynamic range for a standard known as BT.2100. The HLG standard is royalty free and is compatible with SDR displays as well as HDR displays. HLG is supported by HDMI 2.0b*, HEVC, and VP9. The key appeal of HLG is that HDR content can be reasonably viewed on SDR displays.
*Since HLG has no metadata, HLG works with any HDMI spec and HDMI 2.0b is a clarification of HDMI 2.0a
You need to be able to view and display your HDR materials to compatible monitors during post production. AJA Desktop solutions make this simple with support provided in AJA Control Panel for setup of HDR metadata and HLG.
* Check with your software manufacturer for compatibility.
**HLG support is application dependent. Check with your software manufacturer for compatibility.
Hi5-4K-Plus Mini-Converter for HDR and high frame rate support
Standards for HDR over SDI are still evolving and HDMI 2.0 HDR capable displays are affordable and available.
Look to AJA's popular 3G-SDI to HDMI Hi5-4K-Plus Mini-Converter for HDR10 and HLG workflows to feed your display.
Use AJA's free Mini-Config application along with Hi5-4K-Plus to author HDMI HDR Infoframe Metadata as defined in CTA-861-G and HDMI 2.0a.
Plug in, set your static metadata when necessary, and go.Hi5-4K-Plus
You've been handed an HDR signal over HDMI and need to know more about the HDR metadata being utilized. Connect your HDMI 2.0 cable from the source to AJA's HA5-4K HDMI to SDI Mini-Converter and open AJA's free Mini-Config software to its HDR tab for a read out of any HDR static metadata present.HA5-4K