// ==================================================================================
//	YUV to RGB color transform functions
//
//				SGI Indy R5000		PIII 500MHz
//					-O3			-O3
//	Floating Point: 	12.38	6.27		4.57	3.71
//	Fixed Point:     	 7.44	2.78		1.45	0.55		
// ==================================================================================
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define CONV_NUM	(640 * 480 * 30)	// 640x480 pixels, 30 fps.

//
//	Floating point defines
//
#define FP_C_1  (-1.40200)
#define FP_C_2	(-0.34414)
#define FP_C_3	( 0.71414)
#define FP_C_4	( 1.77200)
#define FP_HALF	( 0.50000)
  
void FP_YUV_to_RGB(int Y, int U, int V, int *pR, int *pG, int *pB)
{
	U -= 127;
	V -= 127;
	*pR = (int) (Y + FP_C_1 * V + FP_HALF);
	*pG = (int) (Y + FP_C_2 * U + FP_C_3 * V + FP_HALF);
	*pB = (int) (Y + FP_C_4 * U + FP_HALF);
}

//
//	Fixed point defines
//
#define YUV_SHIFT 	16
#define YUV_ONE		(1 << YUV_SHIFT)
#define YUV_HALF	(1 << (YUV_SHIFT - 1))

#define C_1   ((int)(-1.40200 * YUV_ONE))  
#define C_2   ((int)(-0.34414 * YUV_ONE))
#define C_3   ((int)( 0.71414 * YUV_ONE))     
#define C_4   ((int)( 1.77200 * YUV_ONE))  

void YUV_to_RGB(int Y, int U, int V, int *pR, int *pG, int *pB)
{
	U -= 127;
	V -= 127;
	*pR = Y + ((C_1 * V + YUV_HALF) >> YUV_SHIFT);
	*pG = Y + ((C_2 * U + C_3 * V + YUV_HALF) >> YUV_SHIFT);
	*pB = Y + ((C_4 * U + YUV_HALF ) >> YUV_SHIFT);
}

//
//	Test program
//
main() {
	int Y = rand() % 256;
	int U = rand() % 256;
	int V = rand() % 256;
	volatile int R, G, B;	// Prevents code elimination with -O3
	int i;
	clock_t start, finish;

	// Floating point math
	start = clock();
	for(i=0; i<CONV_NUM; i++)
		FP_YUV_to_RGB(Y, U, V, &R, &G, &B);
	finish = clock();
	printf("Floating Point:\t%f seconds\n", 
		((double) (finish - start)) / CLOCKS_PER_SEC); 

	// Fixed point math
	start = clock();
	for(i=0; i<CONV_NUM; i++)
		YUV_to_RGB(Y, U, V, &R, &G, &B);
	finish = clock();
	printf("Fixed Point:\t%f seconds\n", 
		((double) (finish - start)) / CLOCKS_PER_SEC); 

}