Dolby Vision IQ Explained

Dolby Vision IQ is an update that is designed to adjust the picture based on the ambient room light levels, while trying to maintain the creative intent of the content creator. Ambient illumination has the effect of reducing the dynamic range of the display making it difficult to discern dark details. LG and Panasonic TVs are the first to implement Dolby Vision IQ.

Solutions to this problem have been developed using the TV’s light sensor to first measure the level of ambient light and then boost the backlight to increase overall display brightness. This works to some degree with the result being an increase in the black level and possible shifts in the mid-tones, thus impacting the perception of the picture compared to viewing in a dark room. Plus, some algorithms can be slow creating surges in the backlight level which can be very distracting.

Dolby Vision IQ and solutions like Samsung’s Adaptive Picture attempt to make smarter adjustments. Dolby Vision IQ uses the TV’s light sensor which only measures light intensity, not its spectral make-up. Using this information, Dolby Vision IQ adjusts both the backlight level as well as the PQ curve when watching HDR content to try to maintain creative intent. Dolby Vision only has three points to make adjustments to the PQ curve, but Dolby says it is enough to get better picture quality. This is probably mostly aimed at providing a boost in the darker tones while minimizing crushing the blacks.

The concept uses dynamic metadata to make the adjustments on a scene by scene basis, but Dolby Vision IQ only adjusts the luminance, not the colors. Adjusting colors would require knowledge of the spectrum of the light in the room plus a good HDR and SDR color appearance model to drive the color remapping. No one has that capability yet.

Samsung’s Adaptive Picture appears to work in a similar manner but leverages the HDR10+ Bezier functions built into their processor. This allows for more adjustment points along the PQ curve for better control and an increased ability to try to maintain creative intent. As one person put it, Dolby Vision IQ is like have a bass and treble adjustment whereas Adaptive Picture is like having a multi-band equalizer.

Dolby Vision IQ also has an automatic genre selection mode to identify the type of content being viewed and switches into the appropriate preset mode (sports, movie, games, etc.). The algorithm can adjust the color temperature based on the content, too. For example, snow would look yellow if D65 were chosen so a much bluer color temp (9300K) is used so that white snow looks more like it does in the real world.

Dolby says it is also thinking of the next steps in this algorithm. For example, they recognize that high contrast HDR scenes can exhibit more judder, especially in filmmaker mode. Therefore, they are trying to develop a solution that allows the colorist to define the noise, sharpness and motion processing in a scene to optimize for consumer TVs. This sounds great in theory, but each TV SoC is likely to implement any metadata differently, making the picture unpredictable. More work needs to be done here.

Dolby Vision IQ and Adaptive Picture are geared toward improving HDR picture quality. But what happens when you are watching SDR content with the lights on? Apparently, a simple backlight boost.

While Filmmaker mode received a lot of promotion at CES, I am not a fan. That’s because Filmmaker mode turns off all the picture processing (motion, noise, sharpness) to theoretically recreate what the content creator intended. But TVs don’t behave like grading monitors. As a result, high-contrast scenes in HDR content can exhibit increased judder especially on larger TV screens, in addition to sometimes objectionable motion blur and noise. When SDR content is viewed in Filmmaker mode, the full screen luminance is capped at 100 nits and the gamma is set to 2.4. This is much closer to what the colorist sees in the grading suite, but it is likely to look too dark to most consumers. Both of these issues – lower brightness with SDR and increased judder with HDR may make many consumers want to turn off Filmmaker mode.

LG and Panasonic recognize these concerns. Panasonic specifically announced what they call “Intelligent Sensing” designed to work with both SDR and non-Dolby Vision HDR content when operating in Filmmaker mode. It uses the light sensor to adjust the picture, but details of how it works were not revealed. (Philips has also highlighted in its 2020 European launch that it is using AI to detect different types of content and optimise appropriately – Editor)

Dolby, Samsung and Panasonic showed nice demos of Dolby Vision IQ, Adaptive Picture and Intelligent Sensing at CES, which are good steps in the right direction, but more can and will be done. Let’s see how consumers react, however.

This article first appeared on Display Daily.

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