Autoscaling software JPEG decoder for embedded systems

This paper presents an autoscaling software JPEG decoder with very small memory footprint. An efficient Huffman table processing and fast IDCT calculations make it suitable for embedded systems. Decoding is achieved by processing one MCU at a time and storing it immediately in frame buffer, instead of processing full image strip. There are three modes of downscaling, where 1/8 is extremely fast since it completely bypasses time-consuming decoding operations. Decoder is implemented on microcontroller ARM Cortex M4 using some SIMD instructions for fixed point operations.