While a lot of episodic and movie content is available in HDR, live broadcast content is not. And so far, only Sinclair Broadcasting has led that charge to offer live HDR content using ATSC 3.0 and Advanced HDR by Technicolor. Can this be a key enabler for more live HDR content – especially in sports? Let’s dig in.
Advanced HDR by Technicolor technology (also known as SL-HDR) a collaboration between Philips, InterDigital and Technicolor, had several important announcements and demonstrations at NAB 2023. This technology is used in the broadcast space to enable the capture of content from both HDR and SDR cameras to create an HDR master but also an SDR version with dynamic metadata. What is broadcast is this SDR plus metadata stream that allows compatibility with all SDR playback devices with the HDR version possible on HDR-capable devices as long as it has the SL-HDR decoder to read and recreate the HDR signal.
The technology is well established in the Next Generation TV ATSC 3.0 ecosystem with Sinclair Broadcasting currently using Advanced HDR by Technicolor on 35 channels 24/7 using this single stream to support SDR or HDR playback. Some Hisense TVs now have an ATSC tuner and the SL-HDR decoder to allow up-conversion to HDR. The diagram below shows how how a single stream is currently delivering SDR and HDR images to consumers in the Las Vegas market.
But can anyone see this content? The answer appears to be yes, but the audience remains small. Some newer TVs have this tuner, but not many mobile platforms yet. And they need the ATSC 3.0 tuner and SL-HDR decoder to convert the broadcast SDR signal to HDR.
Prior to NAB, InterDigital hosted a webinar that included key partners in its content production and delivery ecosystem. Speakers included representatives from BBright, Cobalt Digital, Advanced HDR by Technicolor, Sinclair, Cinnafilm and MainConcept.
Cinnafilm, for example, uses the Intelligent Tone Mapping (ITM) feature to automatically create the dynamic metadata for legacy SDR content to enable it to have an HDR look, yet being sensitive to the original SDR creative intent.
The Advanced HDR by Technicolor representative noted that this upconversion process was developed by colorists and was especially tuned for live broadcasts. It is also dynamic metadata creation vs. static which is critical for live sports or other applications that have varying lighting conditions.
One of the thornier issues with broadcasters moving to an HDR master for live production has been the insertion of graphics in the SDR version. Using static conversion results in varying brightness of the graphics which can be very distracting for the viewer.
At NAB 2023, Advanced HDR by Technicolor announced a new static diffuse white feature to help broadcasters and content creators better manage conversions by carefully managing luminance levels. The feature sets a fixed HDR diffuse white level corresponding to the white level at which the graphics are inserted in HDR content and a fixed SDR diffuse white level corresponding to the SDR level to which the HDR diffuse white level is converted. All the HDR content below that HDR diffuse white setting is dynamically down-converted to SDR, up to the SDR diffuse white setting. All the specular HDR content above that HDR diffuse white setting is converted to SDR above the SDR diffuse white setting, allowing the preservation of highlights. This ensures the most appropriate conversion and allows content creators and broadcasters to adjust the content’s brightness, saturation, and contrast.
According to Interdigital’s Valerie Allie, the user can set the diffuse HDR and diffuse SDR white levels. A typical diffuse white HDR level might be 203 nits, for example, as SMPTE has specified and 100 nits for diffuse SDR white. However, even if the operator does not set these, they will be set automatically apparently by looking at the range of luminances in the camera feeds.
Allie also emphasized that the tone mapping that is done is dynamic so there is no set tone curve. To create the tone curve for the frame, a histogram of luminance values is first created to get a strating point for the tone mapping. Then, using machine learning and input from colorists, an optimal tone curve is created for that scene. This sounds similar to the process used by the HDR10+ group.
A demonstration of dynamic metadata management for live sports production was produced by MainConcept and BBright in the UltraHD Forum pavilion. BBright’s contributed recorded live HDR content in the material exchange format (MXF) using the SL-HDR dynamic metadata technology. This was encoded in HEVC with the MainConcept Live Encoder for playback on a Hisense U8 TV.
“Encapsulating the metadata within the compressed bitstream means that we can process it without impacting compression quality,” says Thomas Kramer, VP of Strategy and Business Development at MainConcept.” The MainConcept Live Encoder is able to frame-accurately append its HDR metadata to the core content. This brings broadcasters the right tool to support SDR content with legacy consumer devices while enhancing the same signal to a greater user experience on HDR-enabled TVs,” concluded Kramer.
“This is the first time that the industry will see the ability to store SDR with the SL-HDR metadata so that we can reconstruct either format at any stage in the chain,” says Valérie Allié, Video Solutions Group Director at InterDigital.
Also at NAB, Cobalt Digital showed off their 9904-UDX-4K openGear processing cards, providing ITM and SL-HDR encoding tools implementation which now include the newly developed HDR to SDR dynamic down-mapping with static diffuse white feature for graphics management.
In addition, the Low Complexity Enhancement Video Codec (LCEVC) team showcased Brazil’s SBTVD TV2.5 broadcast encoding solution, with MainConcept’s AVC/H.264 video encoder and Advanced HDR by Technicolor solutions.
So the question remains: what will drive faster adoption of HDR in live programming, especially sports? Maybe ATSC 3.0 and Advanced HDR by Technicolor is the key.