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/*
 * NV12ToARGB color space conversion CUDA kernel
 *
 * This sample uses CUDA to perform a simple NV12 (YUV 4:2:0 planar)
 * source and converts to output in ARGB format
 */

#if !defined CUDA_DISABLER

#include "opencv2/gpu/device/common.hpp"

namespace cv { namespace gpu { namespace device {
    namespace video_decoding
    {
        __constant__ uint constAlpha = ((uint)0xff << 24);

        __constant__ float constHueColorSpaceMat[9];

        void loadHueCSC(float hueCSC[9])
        {
            cudaSafeCall( cudaMemcpyToSymbol(constHueColorSpaceMat, hueCSC, 9 * sizeof(float)) );
        }

        __device__ void YUV2RGB(const uint* yuvi, float* red, float* green, float* blue)
        {
            float luma, chromaCb, chromaCr;

            // Prepare for hue adjustment
            luma     = (float)yuvi[0];
            chromaCb = (float)((int)yuvi[1] - 512.0f);
            chromaCr = (float)((int)yuvi[2] - 512.0f);

           // Convert YUV To RGB with hue adjustment
           *red   = (luma     * constHueColorSpaceMat[0]) +
                    (chromaCb * constHueColorSpaceMat[1]) +
                    (chromaCr * constHueColorSpaceMat[2]);

           *green = (luma     * constHueColorSpaceMat[3]) +
                    (chromaCb * constHueColorSpaceMat[4]) +
                    (chromaCr * constHueColorSpaceMat[5]);

           *blue  = (luma     * constHueColorSpaceMat[6]) +
                    (chromaCb * constHueColorSpaceMat[7]) +
                    (chromaCr * constHueColorSpaceMat[8]);
        }

        __device__ uint RGBAPACK_10bit(float red, float green, float blue, uint alpha)
        {
            uint ARGBpixel = 0;

            // Clamp final 10 bit results
            red   = ::fmin(::fmax(red,   0.0f), 1023.f);
            green = ::fmin(::fmax(green, 0.0f), 1023.f);
            blue  = ::fmin(::fmax(blue,  0.0f), 1023.f);

            // Convert to 8 bit unsigned integers per color component
            ARGBpixel = (((uint)blue  >> 2) |
                        (((uint)green >> 2) << 8)  |
                        (((uint)red   >> 2) << 16) |
                        (uint)alpha);

            return ARGBpixel;
        }

        // CUDA kernel for outputing the final ARGB output from NV12

        #define COLOR_COMPONENT_BIT_SIZE 10
        #define COLOR_COMPONENT_MASK     0x3FF

        __global__ void NV12ToARGB(uchar* srcImage, size_t nSourcePitch,
                                   uint* dstImage, size_t nDestPitch,
                                   uint width, uint height)
        {
            // Pad borders with duplicate pixels, and we multiply by 2 because we process 2 pixels per thread
            const int x = blockIdx.x * (blockDim.x << 1) + (threadIdx.x << 1);
            const int y = blockIdx.y *  blockDim.y       +  threadIdx.y;

            if (x >= width || y >= height)
                return;

            // Read 2 Luma components at a time, so we don't waste processing since CbCr are decimated this way.
            // if we move to texture we could read 4 luminance values

            uint yuv101010Pel[2];

            yuv101010Pel[0] = (srcImage[y * nSourcePitch + x    ]) << 2;
            yuv101010Pel[1] = (srcImage[y * nSourcePitch + x + 1]) << 2;

            const size_t chromaOffset = nSourcePitch * height;

            const int y_chroma = y >> 1;

            if (y & 1)  // odd scanline ?
            {
                uint chromaCb = srcImage[chromaOffset + y_chroma * nSourcePitch + x    ];
                uint chromaCr = srcImage[chromaOffset + y_chroma * nSourcePitch + x + 1];

                if (y_chroma < ((height >> 1) - 1)) // interpolate chroma vertically
                {
                    chromaCb = (chromaCb + srcImage[chromaOffset + (y_chroma + 1) * nSourcePitch + x    ] + 1) >> 1;
                    chromaCr = (chromaCr + srcImage[chromaOffset + (y_chroma + 1) * nSourcePitch + x + 1] + 1) >> 1;
                }

                yuv101010Pel[0] |= (chromaCb << ( COLOR_COMPONENT_BIT_SIZE       + 2));
                yuv101010Pel[0] |= (chromaCr << ((COLOR_COMPONENT_BIT_SIZE << 1) + 2));

                yuv101010Pel[1] |= (chromaCb << ( COLOR_COMPONENT_BIT_SIZE       + 2));
                yuv101010Pel[1] |= (chromaCr << ((COLOR_COMPONENT_BIT_SIZE << 1) + 2));
            }
            else
            {
                yuv101010Pel[0] |= ((uint)srcImage[chromaOffset + y_chroma * nSourcePitch + x    ] << ( COLOR_COMPONENT_BIT_SIZE       + 2));
                yuv101010Pel[0] |= ((uint)srcImage[chromaOffset + y_chroma * nSourcePitch + x + 1] << ((COLOR_COMPONENT_BIT_SIZE << 1) + 2));

                yuv101010Pel[1] |= ((uint)srcImage[chromaOffset + y_chroma * nSourcePitch + x    ] << ( COLOR_COMPONENT_BIT_SIZE       + 2));
                yuv101010Pel[1] |= ((uint)srcImage[chromaOffset + y_chroma * nSourcePitch + x + 1] << ((COLOR_COMPONENT_BIT_SIZE << 1) + 2));
            }

            // this steps performs the color conversion
            uint yuvi[6];
            float red[2], green[2], blue[2];

            yuvi[0] =  (yuv101010Pel[0] &   COLOR_COMPONENT_MASK    );
            yuvi[1] = ((yuv101010Pel[0] >>  COLOR_COMPONENT_BIT_SIZE)       & COLOR_COMPONENT_MASK);
            yuvi[2] = ((yuv101010Pel[0] >> (COLOR_COMPONENT_BIT_SIZE << 1)) & COLOR_COMPONENT_MASK);

            yuvi[3] =  (yuv101010Pel[1] &   COLOR_COMPONENT_MASK    );
            yuvi[4] = ((yuv101010Pel[1] >>  COLOR_COMPONENT_BIT_SIZE)       & COLOR_COMPONENT_MASK);
            yuvi[5] = ((yuv101010Pel[1] >> (COLOR_COMPONENT_BIT_SIZE << 1)) & COLOR_COMPONENT_MASK);

            // YUV to RGB Transformation conversion
            YUV2RGB(&yuvi[0], &red[0], &green[0], &blue[0]);
            YUV2RGB(&yuvi[3], &red[1], &green[1], &blue[1]);

            // Clamp the results to RGBA

            const size_t dstImagePitch = nDestPitch >> 2;

            dstImage[y * dstImagePitch + x     ] = RGBAPACK_10bit(red[0], green[0], blue[0], constAlpha);
            dstImage[y * dstImagePitch + x + 1 ] = RGBAPACK_10bit(red[1], green[1], blue[1], constAlpha);
        }

        void NV12ToARGB_gpu(const PtrStepb decodedFrame, PtrStepSz<uint> interopFrame, cudaStream_t stream)
        {
            dim3 block(32, 8);
            dim3 grid(divUp(interopFrame.cols, 2 * block.x), divUp(interopFrame.rows, block.y));

            NV12ToARGB<<<grid, block, 0, stream>>>(decodedFrame.data, decodedFrame.step, interopFrame.data, interopFrame.step,
                interopFrame.cols, interopFrame.rows);

            cudaSafeCall( cudaGetLastError() );

            if (stream == 0)
                cudaSafeCall( cudaDeviceSynchronize() );
        }
    }
}}}

#endif /* CUDA_DISABLER */
