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D3DDDI_RATIONAL structure (d3dukmdt.h)

  • Article

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).

Syntax

typedef struct _D3DDDI_RATIONAL {
  [in] UINT Numerator;
  [in] UINT Denominator;
} D3DDDI_RATIONAL;

Members

[in] Numerator

The numerator of the frequency fraction.

[in] Denominator

The denominator of the frequency fraction.

Remarks

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.

Requirements

Requirement Value
Minimum supported client Available in Windows Vista and later versions of the Windows operating systems.
Header d3dukmdt.h (include D3dukmdt.h)