rgb24_to_yuv420p源代码

来源：互联网发布：赵薇马云关系知乎编辑：程序博客网时间：2024/05/29 12:41

其中：
lum就对应AVFrame中的data[0]，cb对应AVFrame中的data[1]，cr对应AVFrame中的data[2]，
src就是RGB24的缓冲区地址了。

#define SCALEBITS 8
#define ONE_HALF  (1 << (SCALEBITS - 1))
#define FIX(x) ((int) ((x) * (1L<<SCALEBITS) + 0.5))
typedef unsigned char uint8_t;

static void rgb24_to_yuv420p(uint8_t *lum, uint8_t *cb, uint8_t *cr,
                           uint8_t *src, int width, int height)
{
int wrap, wrap3, x, y;
int r, g, b, r1, g1, b1;
uint8_t *p;

wrap = width;
wrap3 = width * 3;
p = src;
for(y=0;y<height;y+=2) {
      for(x=0;x<width;x+=2) {
         r = p[0];
         g = p[1];
         b = p[2];
         r1 = r;
         g1 = g;
         b1 = b;
         lum[0] = (FIX(0.29900) * r + FIX(0.58700) * g +
                  FIX(0.11400) * b + ONE_HALF) >> SCALEBITS;
         r = p[3];
         g = p[4];
         b = p[5];
         r1 += r;
         g1 += g;
         b1 += b;
         lum[1] = (FIX(0.29900) * r + FIX(0.58700) * g +
                  FIX(0.11400) * b + ONE_HALF) >> SCALEBITS;
         p += wrap3;
         lum += wrap;

         r = p[0];
         g = p[1];
         b = p[2];
         r1 += r;
         g1 += g;
         b1 += b;
         lum[0] = (FIX(0.29900) * r + FIX(0.58700) * g +
                  FIX(0.11400) * b + ONE_HALF) >> SCALEBITS;
         r = p[3];
         g = p[4];
         b = p[5];
         r1 += r;
         g1 += g;
         b1 += b;
         lum[1] = (FIX(0.29900) * r + FIX(0.58700) * g +
                  FIX(0.11400) * b + ONE_HALF) >> SCALEBITS;

         cb[0] = ((- FIX(0.16874) * r1 - FIX(0.33126) * g1 +
                  FIX(0.50000) * b1 + 4 * ONE_HALF - 1) >> (SCALEBITS + 2)) + 128;
         cr[0] = ((FIX(0.50000) * r1 - FIX(0.41869) * g1 -
                  FIX(0.08131) * b1 + 4 * ONE_HALF - 1) >> (SCALEBITS + 2)) + 128;

         cb++;
         cr++;
         p += -wrap3 + 2 * 3;
         lum += -wrap + 2;
      }
      p += wrap3;
      lum += wrap;
}
}