Set-Top Box Format Conversion Circuit for HDR SDR Luminance Matching
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Solution Overview
Problem
Set-top boxes (STBs) face challenges in converting image signals between high dynamic range (HDR) and standard dynamic range (SDR) formats, leading to degraded image display due to mismatched maximum luminance values between the STB and display devices, even with luminance adjustment functions.
Innovation Solution
A format conversion circuit within the STB, comprising an electro-optical transfer function (EOTF) circuit, color space conversion circuit, and opto-electrical transfer function (OETF) circuit, generates output image signals matching the maximum luminance of the display device, ensuring direct display without luminance adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the STB converts image signals from HDR to SDR or from SDR to HDR, then the image signal format is compatible with the television, but the maximum luminance value outputted by the STB differs from the maximum luminance value that can be displayed by the display panel, resulting in degraded image display
Solution Approach 1:
The patent changes the luminance parameter of the image signal by introducing a luminance mapping function that transforms the luminance values based on the display device's maximum luminance capability. The mapping circuit adjusts the luminance parameter dynamically to match the display device's characteristics, resolving the contradiction between format compatibility and luminance accuracy.
Solution Approach 2:
The patent performs preliminary luminance mapping before the image signal is displayed. The mapping circuit pre-adjusts the luminance values according to the display device's maximum luminance, so that when the signal reaches the display device, the luminance values are already optimized and no further degradation occurs.
2Adaptability or versatility
If the television uses a luminance adjustment function to compensate for luminance mismatch, then some display compatibility is achieved, but the display quality is still affected due to inadequate adjustment function
Solution Approach 1:
The patent moves the luminance adjustment action from the display device side to the STB side. By performing the luminance mapping in advance at the STB, the system eliminates the need for inadequate luminance adjustment functions at the television, thereby preserving display quality while maintaining compatibility.
Solution Approach 2:
The patent introduces a luminance mapping function as an intermediary between the image signal source and the display device. This intermediary component (the mapping circuit) transforms the luminance values to be suitable for the display device, avoiding the need for the display device to perform quality-degrading adjustments.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution ensures that the maximum luminance of the output image signal equals the display device's maximum luminance, preventing image degradation by avoiding unnecessary luminance compression or extension, thus maintaining optimal display quality.
Implementation Method 1
The EOTF circuit converts an input image signal having a first format to a first optical signal
Implementation Method 2
The OETF circuit, coupled to the mapping circuit, converts the second optical signal to an output image signal
Data Source
AI summary
A format conversion circuit applied to a set-top box (STB), which is coupled to a display device, is disclosed. The format conversion circuit includes an electro-optical transfer function (EOTF) circuit, a mapping circuit and an opto-electronic transfer (OEFT) circuit. The EOTF circuit converts an input image signal having a first format to a first optical signal. The mapping circuit, coupled to the EOTF circuit, converts the first optical signal to a second optical signal having a second format, wherein at least one of the first optical signal and the second optical signal is generated according to a maximum luminance of the display device. The OETF circuit, coupled to the mapping circuit, converts the second optical signal to an output image signal.