VkVideoEncodeRgbRangeCompressionFlagBitsVALVE

The video encode R′G′B′ range compression to be applied to color component values of the encode input picture before video coding is defined by the rgbRange member of the VkVideoEncodeSessionRgbConversionCreateInfoVALVE structure.

The VkVideoEncodeRgbRangeCompressionFlagBitsVALVE enum describes whether color components are encoded using the full range of numerical values or whether values are reserved for headroom and foot room:

typedef enum VkVideoEncodeRgbRangeCompressionFlagBitsVALVE {
    VK_VIDEO_ENCODE_RGB_RANGE_COMPRESSION_FULL_RANGE_BIT_VALVE = 0x00000001,
    VK_VIDEO_ENCODE_RGB_RANGE_COMPRESSION_NARROW_RANGE_BIT_VALVE = 0x00000002,
} VkVideoEncodeRgbRangeCompressionFlagBitsVALVE;

pub struct VideoEncodeRgbRangeCompressionFlagBitsVALVE(u32);
impl VideoEncodeRgbRangeCompressionFlagBitsVALVE {
    pub const FULL_RANGE: Self = 0x00000001;
    pub const NARROW_RANGE: Self = 0x00000002;
}

• VK_VIDEO_ENCODE_RGB_RANGE_COMPRESSION_FULL_RANGE_BIT_VALVE specifies the following transformations are applied:$$\begin{aligned} Y' &= C'*{rgba}\[G] \\\ C\_B &= C'*{rgba}\[B] - {{2^{(n-1)}}\over{(2^n) - 1}} \\\ C\_R &= C'\_{rgba}\[R] - {{2^{(n-1)}}\over{(2^n) - 1}} \end{aligned}$$
  These formulae correspond to the full range encoding in the Quantization schemes chapter of the Khronos Data Format Specification.Should any future amendments be made to the ITU specifications from which these equations are derived, the formulae used by Vulkan may also be updated to maintain parity.
• VK_VIDEO_ENCODE_RGB_RANGE_COMPRESSION_NARROW_RANGE_BIT_VALVE specifies the following transformations are applied:$$\begin{aligned} Y' &= {{C'*{rgba}\[G] \times (2^n-1) - 16\times 2^{n-8}}\over{219\times 2^{n-8}}} \\\ C\_B &= {{C'*{rgba}\[B] \times \left(2^n-1\right) - 128\times 2^{n-8}}\over{224\times 2^{n-8}}} \\\ C\_R &= {{C'\_{rgba}\[R] \times \left(2^n-1\right) - 128\times 2^{n-8}}\over{224\times 2^{n-8}}} \end{aligned}$$
  These formulae correspond to the narrow range encoding in the Quantization schemes chapter of the Khronos Data Format Specification.Unlike sampler Y′C_BC_R range expansion, no precision guarantees are made for video encode R′G′B′ range compression.
• n is the bit-depth of the components in the bound video session’s pictureFormat.