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IMFVideoPositionMapper::MapOutputCoordinateToInputStream method (evr.h)

  • Artículo

[The component described on this page, Enhanced Video Renderer, is a legacy feature. It has been superseded by the Simple Video Renderer (SVR) exposed through the MediaPlayer and IMFMediaEngine components. To play video content you should send data into one of these components and allow them to instantiate the new video renderer. These components have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use MediaPlayer or the lower level IMFMediaEngine APIs to play video media in Windows instead of the EVR, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

Maps output image coordinates to input image coordinates. This method provides the reverse transformation for components that map coordinates on the input image to different coordinates on the output image.

Syntax

HRESULT MapOutputCoordinateToInputStream(
  [in]  float xOut,
  [in]  float yOut,
  [in]  DWORD dwOutputStreamIndex,
  [in]  DWORD dwInputStreamIndex,
  [out] float *pxIn,
  [out] float *pyIn
);

Parameters

[in] xOut

X-coordinate of the output image, normalized to the range [0...1].

[in] yOut

Y-coordinate of the output image, normalized to the range [0...1].

[in] dwOutputStreamIndex

Output stream index for the coordinate mapping.

[in] dwInputStreamIndex

Input stream index for the coordinate mapping.

[out] pxIn

Receives the mapped x-coordinate of the input image, normalized to the range [0...1].

[out] pyIn

Receives the mapped y-coordinate of the input image, normalized to the range [0...1].

Return value

The method returns an HRESULT. Possible values include, but are not limited to, those in the following table.

Return code Description
S_OK
 The method succeeded.
MF_E_SHUTDOWN
 The video renderer has been shut down.

Remarks

In the following diagram, R(dest) is the destination rectangle for the video. You can obtain this rectangle by calling IMFVideoDisplayControl::GetVideoPosition. The rectangle R1 is a substream within the video. The point P has pixel coordinates (x,y) relative to R(dest).

Illustration showing a rectangle labeled R dest surrounding one labeled R1, which contains a point P located at (x,y)

The position of P relative to R(dest) in normalized coordinates is calculated as follows:

float xn = float(x + 0.5) / widthDest;
float xy = float(y + 0.5) / heightDest;

where widthDest and heightDest are the width and height of R(dest) in pixels.

To calculate the position of P relative to R1, call MapOutputCoordinateToInputStream as follows:

float x1 = 0, y1 = 0;
hr = pMap->MapOutputCoordinateToInputStream(xn, yn, 0, dwInputStreamIndex, &x1, &y1);

The values returned in x1 and y1 are normalized to the range [0...1]. To convert back to pixel coordinates, scale these values by the size of R1:

int scaledx = int(floor(x1 * widthR1));
int scaledy = int(floor(xy * heightR1));

Note that x1 and y1 might fall outside the range [0...1] if P lies outside of R1.

Requirements

Requirement Value
Minimum supported client Windows Vista [desktop apps only]
Minimum supported server Windows Server 2008 [desktop apps only]
Target Platform Windows
Header evr.h
Library Strmiids.lib

See also

IMFVideoPositionMapper