Source-Based Tone Mapping (SBTM)
HDMI® Source-Based Tone Mapping (SBTM)
For decades, broadcast standards such as Recommendation ITU-R BT.709 defined the color and brightness ranges of broadcast video and television displays based on the physical characteristics of CRT displays. However, today’s TVs and displays are capable of displaying far greater ranges of color and brightness than the CRT displays of the 20th century. HDR technology is now frequently used to map the colors of both standard and high dynamic range content into amazing, immersive color images. HDR enhances video images with a wider range of dark to bright contrast, delivering deeper blacks, brighter whites, and rich detail in both the dark and bright parts in the same image. HDR also supports a greater range of colors.
SBTM optimizes quality of combined content
In today’s environment, not all displays have the same HDR capability; some have different ranges of color and brightness levels than others. This is fine when HDR video such as HDR10 and HLG are sent, because the television will typically map HDR content beyond the display’s capabilities to the brightness and color ranges available. But sometimes, a source device needs to combine different types of content (HDR, SDR, dynamic HDR, graphics) together at the same time. For example, when you view a menu of video thumbnails from a streaming video service, some of the thumbnails might be HDR and others might be SDR, and the menu is rendered using graphics. To optimize the quality of the combined content, processing is needed in the Source device that cannot be performed inside the display.
Source-Based Tone Mapping (SBTM) enables the source to send a video signal that takes full advantage of a specific display’s HDR capability by adjusting its output to take better advantage of each display’s potential. As with other HDR technologies, rather than adopt a fixed set of color and brightness ranges, SBTM allows the Source to adapt to a specific display. SBTM can also be used by PCs and gaming devices to eliminate manual user optimization for HDR.
SBTM doesn’t replace existing HDR technologies such as HDR10, HLG and HDR dynamic metadata systems. Instead, SBTM adds an additional HDR capability to HDMI-enabled products, offering consumers additional high-quality viewing experiences.
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