func: static int yuyvToYuv420Wrapper(SwsContext *c, const uint8_t int srcStride[], int srcSliceY, int uint8_t *dstParam[], int dstStride[]) if ( dstParam [ 3 ] )  fillPlane ( dstParam [ 3 ] , dstStride [ 3 ] , c -> srcW , srcSliceH , srcSliceY , 255 ); static void fillPlane(uint8_t *plane, int stride, int width, int height, int uint8_t val) int i ; uint8_t * ptr = plane + stride * y ; for (i = 0; i < height; i++) memset ( ptr , val , width ); ptr += stride; 