Stereo Local Block Matching

Stereo Local Block Matching example resides in L2/examples/stereolbm directory.

This benchmark tests the performance of stereolbm function with a pair of stereo images. Stereo block matching is a method to estimate the motion of the blocks between the consecutive frames, called stereo pair. The postulate behind this idea is that, considering a stereo pair, the foreground objects will have disparities higher than the background. Local block matching uses the information in the neighboring patch based on the window size, for identifying the conjugate point in its stereo pair. While, the techniques under global method, used the information from the whole image for computing the matching pixel, providing much better accuracy than local methods. But, the efficiency in the global methods are obtained with the cost of resources, which is where local methods stands out.

The tutorial provides a step-by-step guide that covers commands for building and running kernel.

Executable Usage

  • Work Directory(Step 1)

The steps for library download and environment setup can be found in README of L2 folder. For getting the design,

cd L2/examples/stereolbm

  • Build kernel(Step 2)

Run the following make command to build your XCLBIN and host binary targeting a specific device. Please be noticed that this process will take a long time, maybe couple of hours.

export OPENCV_INCLUDE=< path-to-opencv-include-folder >
export OPENCV_LIB=< path-to-opencv-lib-folder >
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:< path-to-opencv-lib-folder >
export DEVICE=< path-to-platform-directory >/< platform >.xpfm
make host xclbin TARGET=hw

  • Run kernel(Step 3)

To get the benchmark results, please run the following command.

make run TARGET=hw

  • Example output(Step 4)

-----------StereoLBM Design---------------
Platform Name: Xilinx
INFO: Device found - xilinx_u200_xdma_201830_2
XCLBIN File Name: krnl_stereolbm
INFO: Importing vision/L2/examples/stereolbm/Xilinx_Stereolbm_L2_Test_vitis_hw_u200/build_dir.hw.xilinx_u200_xdma_201830_2/krnl_stereolbm.xclbin
Loading: 'vision/L2/examples/stereolbm/Xilinx_Stereolbm_L2_Test_vitis_hw_u200/build_dir.hw.xilinx_u200_xdma_201830_2/krnl_stereolbm.xclbin'
    Minimum error in intensity = 0
    Maximum error in intensity = 0
    Percentage of pixels above error threshold = 0
------------------------------------------------------------

Profiling

The StereoLBM design is validated on Alveo U200 board at 300 MHz frequency. The hardware resource utilizations are listed in the following table.

Table 1 Hardware resources for Stereo Local Block Matching

Dataset

LUT

BRAM

FF

DSP

Resolution

NPPC

other params

4K

1

PARALLEL Units - 32, Disparity - 32

19005

26

21113

7

FHD

1

PARALLEL Units - 32, Disparity - 32

19380

13

20670

7

The performance is shown below

Table 2 Performance numbers in terms of FPS (Frames Per Second) for Stereo Local Block Matching

Dataset

FPS(CPU)

FPS(FPGA)

4k (3840x2160)

13

34

Full HD(1920x1080)

35

135