An FPGA 2D-convolution unit based on the CAPH language

Abstract

International audienceConvolution is an important operation in image processing applications, such as edge detection, sharpening , adding blurring and so on. Convolving video streams in real-time is a challenging task for PC systems, however, FPGA devices can successfully be used in these tasks. In this article, the design and implementation of a reconfigurable FPGA architecture for 2D-convolution filtering is described. The filtered frames are calculated at a rate of 103 frames per second for images up to 1200×720 pixel resolution. By using a shift-based arithmetic and circular buffers, the developed FPGA architecture allows to reduce the hardware resources consumption up to 98% compared to the conventional convolution implementations , provides high speed processing and enables to manage large number of different convolution kernels. On the other hand, by using the CAPH language it is possible to reduce the design time up to 75% compared to the plain VHDL design. Furthermore, to maintain high flexibility in concordance with the input video, the developed hardware allows to configure the resolution of the input images with values of 3 × Y up to 1200 × Y , and allows scalability for different sizes of convolution kernels of simple and systematic form. Finally , the developed FPGA architecture for the proposed method was implemented and validated in an FPGA Cyclone II EP2C35F672C6 embedded in an Altera development board DE2

Surface Defect Edge Detection Based on Contourlet Transformation

“…Therefore, the wavelet edge detection or edge detection based on the differential operator are unable to be the best approximation to the defect image edge [3][4][5] . In recent years, Contourlet transform has been widely used in the image processing field [6][7][8] . Contourlet transform is a true two-dimensional image sparse representation method, which can represent the image features of multi-resolution, localization, critical sampling, directionality and anisotropy.…”

A Low Cost Structurally Optimized Design for Diverse Filter Types

“…This coefficient approximation may adversely effects the accuracy of filtered outputs. The second approach is based on reducing the total count of multipliers required by the filter design by reducing effective coefficients count without any change in its value therefore accurately calculates filtered outputs [9, 15–19]. …”

“…The optimization approaches presented in [9] and [15] were mainly focussed on the cost reduction of multipliers by using low cost arithmetic alternatives. In [9], the hardware cost of multiplier is reduced by using distributed arithmetic approach.…”

“…The main limitation of this approach is that the coefficients must remain fixed in order to achieve the benefit of cost reduction [20]. Similarly in [15], multipliers cost was optimized by replacing them with a low cost shift-based arithmetic. The drawback of this method is it’s restrict applicability for only those filter types whose coefficients can be expressed in fractional form in such a way that the numerator and denominator of fraction can be expressed in the power of 2.…”

“…The drawback of this method is it’s restrict applicability for only those filter types whose coefficients can be expressed in fractional form in such a way that the numerator and denominator of fraction can be expressed in the power of 2. Therefore many useful filters such as Gabor filter and many directional filters cannot be implemented with this approach [15]. …”