Dynamic Approximation of JPEG Hardware

JPEG compression based on the discrete cosine transform (DCT) is a key building block in low-power multimedia applications. Approximate computation techniques are used to exploit the error tolerance of JPEG. An image-dependent framework is proposed in this work to design optimized approximate hardware with variable approximate bit-widths for a userspecified error budget. The proposed method can dynamically adjust the extent of approximation in the system depending on the pixel values of the input image, thus leveraging the inherent sparsity of certain images. This novel technique not only improves the power-delay product by 3.4× over the base case, i.e., where the JPEG hardware is accurate, but also significantly outperforms the image-independent approximation case, which is solely based on the error tolerance of the JPEG algorithm.