MFFrameRateToAverageTimePerFrame function (mfapi.h)

Article
02/22/2024

Converts a video frame rate into a frame duration.

Syntax

HRESULT MFFrameRateToAverageTimePerFrame(
  [in]  UINT32 unNumerator,
  [in]  UINT32 unDenominator,
  [out] UINT64 *punAverageTimePerFrame
);

Parameters

[in] unNumerator

The numerator of the frame rate.

[in] unDenominator

The denominator of the frame rate.

[out] punAverageTimePerFrame

Receives the average duration of a video frame, in 100-nanosecond units.

Return value

If this function succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.

Remarks

This function is useful for calculating time stamps on a sample, given the frame rate.

Also, average time per frame is used in the older VIDEOINFOHEADER and VIDEOINFOHEADER2 format structures. This function provides a standard conversion so that all components in the pipeline can use consistent values, if they need to translate between the older format structures and the media type attributes used in Media Foundation.

For certain common frame rates, the function gets the frame duration from a look-up table:

Frames per second (floating point)	Frames per second (fractional)	Average time per frame
59.94	60000/1001	166833
29.97	30000/1001	333667
23.976	24000/1001	417188
60	60/1	166667
30	30/1	333333
50	50/1	200000
25	25/1	400000
24	24/1	416667

Most video content uses one of the frame rates listed here. For other frame rates, the function calculates the duration.

Requirements

Requirement	Value
Minimum supported client	Windows Vista [desktop apps only]
Minimum supported server	Windows Server 2008 [desktop apps only]
Target Platform	Windows
Header	mfapi.h
Library	Mfplat.lib
DLL	Mfplat.dll