DXGI Screen capture distorted image - c++

Question

Not only that the fps drops form 60 to 20-21 but the image also looks distorted like this. Second image is what it should look like
What it looks like
What it should look like
if (captureVideo == 1) {
pNewTexture = NULL;
// Use the IDXGISwapChain::GetBuffer API to retrieve a swap chain surface ( use the uuid ID3D11Texture2D for the result type ).
pSwapChain->GetBuffer( 0, __uuidof( ID3D11Texture2D ), reinterpret_cast< void** >( &pSurface ) );
/* The swap chain buffers are not mapable, so I need to copy it to a staging resource. */
pSurface->GetDesc( &description ); //Use ID3D11Texture2D::GetDesc to retrieve the surface description
// Patch it with a D3D11_USAGE_STAGING usage and a cpu access flag of D3D11_CPU_ACCESS_READ
description.BindFlags = 0;
description.CPUAccessFlags = D3D11_CPU_ACCESS_READ;
description.Usage = D3D11_USAGE_STAGING;
// Create a temporary surface ID3D11Device::CreateTexture2D
HRESULT hr = pDevice->CreateTexture2D( &description, NULL, &pNewTexture );
if( pNewTexture )
{
// Copy to the staging surface ID3D11DeviceContext::CopyResource
pContext->CopyResource( pNewTexture, pSurface );
// Now I have a ID3D11Texture2D with the content of your swap chain buffer that allow you to use the ID3D11DeviceContext::Map API to read it on the CPU
D3D11_MAPPED_SUBRESOURCE resource;
pContext->Map( pNewTexture, D3D11CalcSubresource( 0, 0, 0), D3D11_MAP_READ, 0, &resource );
const int pitch = w << 2;
const unsigned char* source = static_cast< const unsigned char* >( resource.pData );
unsigned char* dest = static_cast< unsigned char* >(m_lpBits);
for( int i = 0; i < h; ++i )
{
memcpy( dest, source, w * 4 );
source += pitch;
dest += pitch;
}
AppendNewFrame(w, h, m_lpBits,24);
pContext->Unmap( pNewTexture, 0);
pNewTexture->Release();
}
}

Answer 1

The code snippet even though incomplete shows several potential problems:
Number of 24 in AppendNewFrame line suggests that you are trying to treat the data as 24-bit RGB, and your data is 32-bit RGB. Such mistreatment matches the artifacts exhibited on the attached images;
Pitch/stride is taken as assumed default, while you have the effectively used one in D3D11_MAPPED_SUBRESOURCE structure and you should be using it.