Mean and Standard Deviation - 2024.1 English

Vitis Libraries

Release Date
2024-05-30
Version
2024.1 English

The meanStdDev function computes the mean and standard deviation of input image. The output Mean value is in fixed point Q8.8 format, and the Standard Deviation value is in Q8.8 format. Mean and standard deviation are calculated as follows:


image137
image138

API Syntax

template<int SRC_T,int ROWS, int COLS,int NPC=1, int XFCVDEPTH_IN = _XFCVDEPTH_DEFAULT>
void meanStdDev(xf::cv::Mat<SRC_T, ROWS, COLS, NPC, XFCVDEPTH_IN> & _src,unsigned short* _mean,unsigned short* _stddev)

Parameter Descriptions

The following table describes the template and the function parameters.

Table 652 Table . meanStdDev Parameter Description
Parameter Description
SRC_T Input and Output pixel type. Only 8-bit, unsigned, 1 and 3 channels are supported (XF_8UC1 and XF_8UC3)
ROWS Number of rows in the image being processed.
COLS Number of columns in the image being processed. Must be a multiple of 8, for 8-pixel operation.
NPC Number of pixels to be processed per cycle; possible options are XF_NPPC1 and XF_NPPC8 for 1 pixel and 8 pixel operations respectively.
XFCVDEPTH_IN Depth of the input image.
XFCVDEPTH_OUT Depth of the output image.
_src Input image
_mean 16-bit data pointer through which the computed mean of the image is returned.
_stddev 16-bit data pointer through which the computed standard deviation of the image is returned.

Resource Utilization

The following table summarizes the resource utilization of the meanStdDev function, generated using Vivado HLS 2019.1 tool for the Xczu9eg-ffvb1156-1-i-es1 FPGA, to process a grayscale HD (1080x1920) image.

Table 653 Table . meanStdDev Function Resource Utilization Summary
Operating Mode Operating Frequency (MHz) Utilization Estimate
BRAM_18K DSP_48Es FF LUT CLB
1 pixel 300 0 6 896 461 121
8 pixel 150 0 13 1180 985 208

The following table summarizes the resource utilization of the meanStdDev function, generated using Vivado HLS 2019.1 tool for the Xczu9eg-ffvb1156-1-i-es1 FPGA, to process a 4K 3Channel image.

Table 654 Table . meanStdDev Function Resource Utilization Summary
Operating Mode Operating Frequency (MHz) Utilization Estimate
BRAM_18K DSP_48Es FF LUT CLB
1 pixel 300 0 7 5075 3324 725

Performance Estimate

The following table summarizes the performance in different configurations, as generated using Vivado HLS 2019.1 tool for the Xczu9eg-ffvb1156-1-i-es1, to process a grayscale HD (1080x1920) image.

Table 655 Table . meanStdDev Function Performance Estimate Summary
Operating Mode Latency Estimate
Max Latency
1 pixel operation (300 MHz) 6.9 ms
8 pixel operation (150 MHz) 1.69 ms