D3DDDI_RATIONAL - NtDoc
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// d3dukmdt.h
typedef struct _D3DDDI_RATIONAL {
[in] UINT Numerator;
[in] UINT Denominator;
} D3DDDI_RATIONAL;
View the official Windows Driver Kit DDI referenceNo description available.
The D3DDDI_RATIONAL structure describes a fractional value that represents vertical and horizontal frequencies of a video mode (that is, vertical sync and horizontal sync).
Numerator [in]The numerator of the frequency fraction.
Denominator [in]The denominator of the frequency fraction.
Vertical and horizontal frequencies are stored in Hertz (Hz). The dynamic range of this encoding format, given 10⁻⁷ resolution, is {0 to (2³² - 1) / 10⁷}. This range translates to {0 to 428.4967296} Hz for vertical and horizontal frequencies. This submicrosecond precision range is acceptable even for a provided application. (An error of one microsecond for video signal synchronization would imply a time drift with a cycle of 10⁷/(60 x 60 x 24) = 115.741 days.)
For a rational number with a finite fractional sequence, use a denominator of the form 10(length of fractional sequence). For a rational number without a finite fractional sequence, a sequence that exceeds the precision that the dynamic range of the denominator allows, or an irrational number, use an appropriate ratio of integers that best represents the value.