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//////////////////////////////////////////////////////////////////////////
//
// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF
// ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO
// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A
// PARTICULAR PURPOSE.
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
//////////////////////////////////////////////////////////////////////////
#pragma once
//-------------------------------------------------------------------
// VideoBufferLock class
//
// Locks a video buffer that might or might not support IMF2DBuffer.
//
//-------------------------------------------------------------------
class VideoBufferLock
{
public:
VideoBufferLock(IMFMediaBuffer *pBuffer) : m_p2DBuffer(NULL), m_bLocked(FALSE)
{
m_pBuffer = pBuffer;
m_pBuffer->AddRef();
// Query for the 2-D buffer interface. OK if this fails.
(void)m_pBuffer->QueryInterface(IID_PPV_ARGS(&m_p2DBuffer));
}
~VideoBufferLock()
{
UnlockBuffer();
SafeRelease(&m_pBuffer);
SafeRelease(&m_p2DBuffer);
}
//-------------------------------------------------------------------
// LockBuffer
//
// Locks the buffer. Returns a pointer to scan line 0 and returns the stride.
//
// The caller must provide the default stride as an input parameter, in case
// the buffer does not expose IMF2DBuffer. You can calculate the default stride
// from the media type.
//-------------------------------------------------------------------
HRESULT LockBuffer(
LONG lDefaultStride, // Minimum stride (with no padding).
DWORD dwHeightInPixels, // Height of the image, in pixels.
BYTE **ppbScanLine0, // Receives a pointer to the start of scan line 0.
LONG *plStride // Receives the actual stride.
)
{
HRESULT hr = S_OK;
DWORD cbMaxLength;
DWORD cbCurrentLength;
// Use the 2-D version if available.
if (m_p2DBuffer)
{
hr = m_p2DBuffer->Lock2D(ppbScanLine0, plStride);
}
else
{
// Use non-2D version.
BYTE *pData = NULL;
hr = m_pBuffer->Lock(&pData, &cbMaxLength, &cbCurrentLength);
if (SUCCEEDED(hr))
{
*plStride = lDefaultStride;
if (lDefaultStride < 0)
{
// Bottom-up orientation. Return a pointer to the start of the
// last row *in memory* which is the top row of the image.
*ppbScanLine0 = pData + abs(lDefaultStride) * (dwHeightInPixels - 1);
}
else
{
// Top-down orientation. Return a pointer to the start of the
// buffer.
*ppbScanLine0 = pData;
}
}
}
m_bLocked = (SUCCEEDED(hr));
return hr;
}
//-------------------------------------------------------------------
// UnlockBuffer
//
// Unlocks the buffer. Called automatically by the destructor.
//-------------------------------------------------------------------
void UnlockBuffer()
{
if (m_bLocked)
{
if (m_p2DBuffer)
{
(void)m_p2DBuffer->Unlock2D();
}
else
{
(void)m_pBuffer->Unlock();
}
m_bLocked = FALSE;
}
}
private:
IMFMediaBuffer *m_pBuffer;
IMF2DBuffer *m_p2DBuffer;
BOOL m_bLocked;
};
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