if(!context) context=getSwsContextFromCmdLine(srcW, srcH, IMGFMT_YV12, dstW, dstH, dstFormat);
if(!context) context=sws_getContextFromCmdLine(srcW, srcH, IMGFMT_YV12, dstW, dstH, dstFormat);
void SwScale_YV12slice(unsigned char* src[], int srcStride[], int srcSliceY ,			     int srcSliceH, uint8_t* dst[], int dstStride, int dstbpp,			     int srcW, int srcH, int dstW, int dstH){	static SwsContext *context=NULL;	int dstFormat;	int dstStride3[3]= {dstStride, dstStride>>1, dstStride>>1};	switch(dstbpp)	{		case 8 : dstFormat= IMGFMT_Y8;		break;		case 12: dstFormat= IMGFMT_YV12;	break;		case 15: dstFormat= IMGFMT_BGR15;	break;		case 16: dstFormat= IMGFMT_BGR16;	break;		case 24: dstFormat= IMGFMT_BGR24;	break;		case 32: dstFormat= IMGFMT_BGR32;	break;		default: return;	}	if(!context) context=getSwsContextFromCmdLine(srcW, srcH, IMGFMT_YV12, dstW, dstH, dstFormat);	context->swScale(context, src, srcStride, srcSliceY, srcSliceH, dst, dstStride3);}