private unsafe bool SearchMotionVector(BitmapData inputData, BitmapData previousData, int pixelBytes, int yStart, int xStart, out MotionVector motionVector)
{
byte* inputPtr = (byte*)inputData.Scan0;
byte* previousPtr = (byte*)previousData.Scan0;
motionVector = MotionVector.ZERO;
// Origin - no translation. This is most probable.
if (TestMotionVector(inputData, previousData, pixelBytes, yStart, xStart, inputPtr, previousPtr, MotionVector.ZERO))
{
return true;
}
foreach (MotionVector favouriteVector in favouriteMotionVectors)
{
if (TestMotionVector(inputData, previousData, pixelBytes, yStart, xStart, inputPtr, previousPtr, favouriteVector))
{
motionVector = favouriteVector;
return true;
}
}
// check possible offsets to find an equal shifted
// block in the previous frame
for (int i = 0; i < mcPossibleOffsets.Length; i++)
{
motionVector = mcPossibleOffsets[i];
if (TestMotionVector(inputData, previousData, pixelBytes, yStart, xStart, inputPtr, previousPtr, motionVector))
{
if (!favouriteMotionVectors.Contains(motionVector))
{
favouriteMotionVectors.AddFirst(motionVector);
if (favouriteMotionVectors.Count > MAX_FAVOURITE_MOTION_VECTORS_SIZE)
{
favouriteMotionVectors.RemoveLast();
}
}
return true;
}
}
return false;
}
private unsafe bool TestMotionVector(BitmapData inputData, BitmapData previousData, int pixelBytes, int yStart, int xStart, byte* inputPtr, byte* previousPtr, MotionVector motionVector)
{
for (int y = yStart; y < yStart + MCBlockSize; y++)
{
byte* inputRow = inputPtr + (y * inputData.Stride);
byte* previousRow = previousPtr + (y * previousData.Stride);
for (int x = xStart; x < xStart + MCBlockSize; x++)
{
int xSource = x + motionVector.x;
int ySource = y + motionVector.y;
if ((x < 0) || (x >= frameWidth) ||
(y < 0) || (y >= frameHeight) ||
(xSource < 0) || (xSource >= frameWidth) ||
(ySource < 0) || (ySource >= frameHeight))
{
return false;
}
// assume BGRA pixel format
for (int band = 0; band < 3; band++)
{
int inputIndex = x * pixelBytes + band;
int previousIndex = motionVector.y * previousData.Stride + xSource * pixelBytes + band;
if (inputRow[inputIndex] != previousRow[previousIndex])
{
// means: inputFrame[x, y] != previousFrame[xSource, ySource])
return false;
}
}
}
}
return true;
}
private unsafe void DecodeTranslatedBlock(Stream inStream, BitmapData currentData, BitmapData previousData, int pixelBytes, int yStart, int xStart, MotionVector motionVector)
{
byte* currentPtr = (byte*)currentData.Scan0;
byte* previousPtr = (byte*)previousData.Scan0;
int debugPixelBytes = pixelBytes;
if (VisualizeMCBlockTypes)
{
debugPixelBytes = GetBytesPerPixel(debugFrame.PixelFormat);
}
bool isIdenticalBlock = (motionVector.x == 0) && (motionVector.y == 0);
for (int y = yStart; y < yStart + MCBlockSize; y++)
{
byte* currentRow = currentPtr + (y * currentData.Stride);
byte* previousRow = previousPtr + ((y + motionVector.y) * previousData.Stride);
byte* debugRow = (byte*)0;
if (VisualizeMCBlockTypes)
{
debugRow = (byte*)debugFrameData.Scan0 + (y * debugFrameData.Stride);
}
for (int x = xStart; x < xStart + MCBlockSize; x++)
{
// assume BGRA input pixel format, store as RGB
for (int band = 2; band >= 0; band--)
{
// temporal prediction
int currentIndex = x * pixelBytes + band;
int previousIndex = currentIndex + motionVector.x * pixelBytes;
currentRow[currentIndex] = previousRow[previousIndex];
}
if (pixelBytes == 4)
{
currentRow[x * pixelBytes + 3] = 255; // assume full alpha
}
if (VisualizeMCBlockTypes)
{
// identical - green
// translated - blue
int index = x * debugPixelBytes;
debugRow[index] = (byte)((isIdenticalBlock) ? 0 : 255);
debugRow[index + 1] = (byte)((isIdenticalBlock) ? 255 : 0);
debugRow[index + 2] = 0;
}
}
}
}
