Median Blur Filter

The function xFMedianBlur performs a median filter operation on the input image. The median filter acts as a non-linear digital filter which improves noise reduction. A filter size of N would output the median value of the NxN neighborhood pixel values, for each pixel.

API Syntax

template<int FILTER_SIZE, int BORDER_TYPE, int TYPE, int ROWS, int COLS, int NPC> 
void xFMedianBlur (xF::Mat<TYPE, ROWS, COLS, NPC> & _src, xF::Mat<TYPE, ROWS, COLS, NPC> & _dst)

Parameter Descriptions

The following table describes the template and the function parameters.

Table 1. xFMedianBlur Function Parameter Descriptions
Parameter	Description
FILTER_SIZE	Window size of the hardware filter for which the hardware kernel will be built. This can be any odd positive integer greater than 1.
BORDER_TYPE	The way in which borders will be processed in the hardware kernel. Currently, only XF_BORDER_REPLICATE is supported.
TYPE	Type of input pixel. XF_8UC1 is supported.
ROWS	Number of rows in the image being processed.
COLS	Number of columns in the image being processed.
NPC	Number of pixels to be processed in parallel. Options are XF_NPPC1 (for 1 pixel processing per clock), XF_NPPC8 (for 8 pixel processing per clock
_src	Input image.
_dst	Output image.

Resource Utilization

The following table summarizes the resource utilization of the xFMedianBlur function for XF_NPPC1 and XF_NPPC8 configurations, generated using Vivado HLS 2017.1 version tool for the Xilinx Xc7z020clg484-1 FPGA.

Table 2. xFMedianBlur Function Resource Utilization Summary
Operating Mode	FILTER_SIZE	Operating Frequency (MHz)	Utilization Estimate
Operating Mode	FILTER_SIZE	Operating Frequency (MHz)	LUTs	FFs	DSPs	BRAMs
1 pixel	3	300	1197	771	0	3
8 pixel	3	150	6559	1595	0	6
1 pixel	5	300	5860	1886	0	5

Performance Estimate

The following table summarizes performance estimates of xFMedianBlur function on Vivado HLS 2017.1 version tool for the Xilinx xczu9eg-ffvb1156-1-i-es1 FPGA.

Table 3. xFMedianBlur Function Performance Estimate Summary
Operating Mode	FILTER_SIZE	Operating Frequency (MHz)	Input Image Size	Latency Estimate
Operating Mode	FILTER_SIZE	Operating Frequency (MHz)	Input Image Size	Max (ms)
1 pixel	3	300	1920x1080	6.99
8 pixel	3	150	1920x1080	1.75
1 pixel	5	300	1920x1080	7.00