Netflix has completed a worldwide technology upgrade that improves video quality for Premium subscribers viewing 4K HDR titles. The move is being hailed as welcome news in the wake of a price hike to $22.99 from $19.99 for U.S. Premium customers. Netflix used the “dynamic optimization” video encoding method to implement an HDR variant of the company’s VMAF (Video Multimethod Assessment Fusion) quality metric. The new HDR-VMAF is the result of a collaboration between Netflix and Dolby Laboratories that employs “subjective tests with 4K HDR content using high-end OLED panels,” according to Netflix.

The subjective tests were conducted using “calibrated conditions created in participants’ homes,” explains a Netflix blog post. According to Tom’s Guide, such tests normally “would be done in lab conditions with test subjects, but the pandemic” created a challenge that led to an at-home method as a workaround, representing years of work.

Announced in 2020, VMAF “uses Netflix’s machine learning-based technology, dubbed ‘Dynamically Optimized (DO) encoding’ to measure HDR quality by focusing on signal characteristics (as a result of lossy encoding) instead of display characteristics,” TV Technology explains. Previously, Netflix used a type of adaptive bitrate streaming.

“HDR-VMAF is format-agnostic, measuring quality equally and independently for Dolby Vision and HDR10 programs, and it calculates scores based on an ‘ideal display’ — one that’s ‘capable of representing the entire luminance range and the entire color gamut spanned by the video signal,’” TechRadar reports.

A major benefit of HDR-VMAF “is that it allowed Netflix to make the transition from fixed bitrate video encoding to using dynamically optimized (HDR-DO) encodes for 4K HDR video streaming,” per TechRadar.

Netflix in June completed the yearlong upgrade of its library to full 4K HDR using HDR-DO. As a result, Premium subscribers can now expect any Dolby Vision or HDR10 content streamed to be optimized using the new 4K HDR quality metric, an improvement meant not only to improve the Netflix viewing experience on large screens, but also on tablets and phones, many of which now support HDR “and even Dolby Vision HDR,” according to TechRadar.