Use an actual cuda kernel to convert RGB to NV12

sunshine/platform/linux/cuda.h

@@ -1,6 +1,8 @@
 #ifndef SUNSHINE_PLATFORM_CUDA_H
 #define SUNSHINE_PLATFORM_CUDA_H
 
+#ifndef __NVCC__
+
 #include "sunshine/platform/common.h"
 #include "x11grab.h"
 
@@ -9,4 +11,48 @@ std::shared_ptr<platf::hwdevice_t> make_hwdevice(int width, int height, platf::x
 int init();
 } // namespace cuda
 
+#else
+namespace platf {
+class img_t;
+}
+#endif
+
+typedef struct cudaArray *cudaArray_t;
+
+#if !defined(__CUDACC__)
+typedef unsigned long long cudaTextureObject_t;
+#else  /* defined(__CUDACC__) */
+typedef __location__(device_builtin) unsigned long long cudaTextureObject_t;
+#endif /* !defined(__CUDACC__) */
+
+namespace cuda {
+class sws_t {
+public:
+  ~sws_t();
+  sws_t(int in_width, int in_height, int out_width, int out_height, int threadsPerBlock);
+
+  /**
+   * in_width, out_width -- The width and height of the captured image in bytes
+   * out_width, out_height -- the width and height of the NV12 image in pixels
+   * 
+   * cuda_device -- pointer to the cuda device
+   */
+  static std::unique_ptr<sws_t> make(int in_width, int in_height, int out_width, int out_height);
+
+  // Converts loaded image into a CUDevicePtr
+  int convert(std::uint8_t *Y, std::uint8_t *UV, std::uint32_t pitchY, std::uint32_t pitchUV);
+
+  void set_colorspace(std::uint32_t colorspace, std::uint32_t color_range);
+
+  int load_ram(platf::img_t &img);
+
+  cudaArray_t array;
+  cudaTextureObject_t texture;
+
+  int width, height;
+
+  int threadsPerBlock;
+};
+} // namespace cuda
+
 #endif