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/**************************************************************************
A/V Stream Camera Sample
Copyright (c) 2001, Microsoft Corporation.
File:
CNV12Synthesizer.h
Abstract:
This file contains the implementation of CNV12Synthesizer.
CNV12Synthesizer is derived from CYUVSynthesizer. It uses the YUV color
space and defines a Commit() function that reformats pixels into the
NV12 format. From MSDN:
A format in which all Y samples are found first in memory as an
array of unsigned char with an even number of lines (possibly with
a larger stride for memory alignment). This is followed immediately
by an array of unsigned char containing interleaved Cb and Cr
samples. If these samples are addressed as a little-endian WORD
type, Cb would be in the least significant bits and Cr would be in
the most significant bits with the same total stride as the Y
samples. NV12 is the preferred 4:2:0 pixel format.
A visual representation of the layout:
YYYY
YYYY
UVUV
History:
created 4/14/2013
**************************************************************************/
#include "Common.h"
/**************************************************************************
LOCKED CODE
**************************************************************************/
#ifdef ALLOC_PRAGMA
#pragma code_seg()
#endif // ALLOC_PRAGMA
_Success_(return > 0)
ULONG
CNV12Synthesizer::
Commit(
_Out_writes_bytes_(Size)
PUCHAR Buffer,
_In_ ULONG Size,
_In_ ULONG Stride
)
/*++
Routine Description:
Copy (and reformat, if necessary) pixels from the internal scratch
buffer. If the output format decimates chrominance, do it here.
Arguments:
Buffer -
The output buffer to fill.
Size -
The size of the output buffer in bytes.
Stride -
The length of a row in bytes.
Return Value:
Number of bytes copied into Buffer.
--*/
{
// In case stride isn't initialized.
if( Stride==0 )
{
Stride = m_OutputStride;
}
// The code actually handles this gracefully. It rounds down.
NT_ASSERT( (m_Width&1) == 0 );
NT_ASSERT( (m_Height&1) == 0 );
// These are impossible conditions.
if( !( Buffer &&
m_Buffer &&
(Size%6)==0 && // Should be evenly divisible by 1 macropixel
Size>=6 // At least 1 macropixel
) )
{
NT_ASSERT(FALSE);
return 0;
}
ULONG MacroPixelsWide = m_Width/2;
// Impossible.
if (MacroPixelsWide == 0 || Stride < (MacroPixelsWide*2)) // 1 macropixel for NV12 is 2 bytes wide
{
NT_ASSERT(FALSE);
return 0;
}
// At most, 2/3rds of the available space is used by the Y plane.
// Notice that we limit the number of macro pixel rows to what will
// fit in the space available, no matter what is in the original.
ULONG Y_limit = (Size /3) * 2;
ULONG MacroPixelsHigh = min(m_Height, Y_limit / Stride) / 2;
// Impossible.
if( MacroPixelsHigh==0 )
{
NT_ASSERT(FALSE);
return 0;
}
// Now we work back to arrive at the Y & UV plane sizes.
ULONG UV_size = Stride * MacroPixelsHigh;
ULONG Y_size = Stride * MacroPixelsHigh * 2;
ULONG YUV_size = Y_size + UV_size;
// Impossible.
if( Size < YUV_size )
{
NT_ASSERT(FALSE);
return 0;
}
PUCHAR pYRow = Buffer;
PUCHAR pUVRow = Buffer + Y_size;
for(ULONG row = 0; row < MacroPixelsHigh; row++)
{
PKS_RGBQUAD pSrc = (PKS_RGBQUAD) GetImageLocation(0, row*2);
PWORD pYUpper = (PWORD)pYRow;
PWORD pYLower = (PWORD)(pYRow + Stride);
PWORD pUV = (PWORD)pUVRow;
for(ULONG col = 0; col < MacroPixelsWide; col++)
{
KS_RGBQUAD TL = pSrc[0];
KS_RGBQUAD TR = pSrc[1];
KS_RGBQUAD BL = pSrc[m_Width+0];
KS_RGBQUAD BR = pSrc[m_Width+1];
pSrc += 2;
// Copy luma first
pYUpper[0] = MAKEWORD(TL.rgbGreen, TR.rgbGreen);
pYLower[0] = MAKEWORD(BL.rgbGreen, BR.rgbGreen);
pYUpper++;
pYLower++;
LONG
tU = TL.rgbBlue; //top left
tU += BL.rgbBlue; //bottom left
tU += TR.rgbBlue; //top right
tU += BR.rgbBlue; //bottom right
LONG
tV = TL.rgbRed; //top left
tV += BL.rgbRed; //bottom left
tV += TR.rgbRed; //top right
tV += BR.rgbRed; //bottom right
// Copy decimated chroma
*pUV++ = MAKEWORD(((tU+2)>>2), ((tV+2)>>2));
}
// A row of macropixels covers two Y rows and one UV row
pYRow += (Stride * 2);
pUVRow += Stride;
}
return (ULONG)(pUVRow - Buffer);
}
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