The approximate hardware design can save huge energy at the cost of errors incurred in the design. This article proposes the approximate algorithm for low-power compressors, utilized to build approximate multiplier with low energy and acceptable error profiles. This article presents two design approaches (DA1 and DA2) for higher bit size approximate multipliers. The proposed multiplier of DA1 have no propagation of carry signal from LSB to MSB, resulted in a very high-speed design. The increment in delay, power, and energy are not exponential with increment of multiplier size ( n ) for DA1 multiplier. It can be observed that the maximum combinations lie in the threshold Error Distance of 5% of the maximum value possible for any particular multiplier of size n . The proposed 4-bit DA1 multiplier consumes only 1.3 fJ of energy, which is 87.9%, 78%, 94%, 67.5%, and 58.9% less when compared to M1, M2, LxA, MxA, accurate designs respectively. The DA2 approach is recursive method, i.e., n -bit multiplier built with n/2-bit sub-multipliers. The proposed 8-bit multiplication has 92% energy savings with Mean Relative Error Distance (MRED) of 0.3 for the DA1 approach and at least 11% to 40% of energy savings with MRED of 0.08 for the DA2 approach. The proposed multipliers are employed in the image processing algorithm of DCT, and the quality is evaluated. The standard PSNR metric is 55 dB for less approximation and 35 dB for maximum approximation.

Integer discrete cosine transform (DCT) is one of the popularly used mathematical operation on image/video applications. These applications has a unique property that the error presence in the output will not degrade the output visual quality. Hardware complexity integer DCT for image/video processing is very high, approximation in the hardware results reduction in area, power and delay without compromising the perceptual quality of the output image. This paper proposes an efficient technique to implement the approximate integer DCT for high efficiency video coding (HEVC). The proposed technique approximates the coefficients of the integer DCT using their structural property and hence multiplier hardware is not required for DCT. The proposed design is approximately 77% efficient in terms of power delay product compared with accurate integer DCT. The Quality of Approximate DCT on Images is estimated using Average PSNR and are found to be 32.17 and 30.13 for 512, 256 size images respectively.