Near-lossless energy-efficient image compression algorithm for wireless capsule endoscopy

New near-lossless algorithm for energy efficient image compression in wireless capsule endoscopy (WCE) is proposed. The designed compressor operates directly on data from CMOS image sensor with the Bayer Color Filter Array (CFA). By optimal combining transform-based coding with predictive coding, the proposed compressor achieves higher average image quality and lower bit rate as compared to significantly more complex JPEG-LS based coding schemes. For typical WCE images, the average compression ratio is 3.9, while the PSNR is 46.5 dB, which means that very high image quality is achieved. The designed image compressor together with 1 KB FIFO (first-in, first-out) stream buffer and a data serializer was implemented in Verilog and synthesised with the UMC 180 nm CMOS process as an intellectual property (IP) core. Integrated FIFO and data serializer facilitate low-cost interface to an RF (radio frequency) transmitter. The silicon area of the core is only 0.96 × 0.54 mm. The IP core, operating at clock frequency as low as 5.25 MHz, is able to process 20 fps (frames per second). It consumes only about 44 μJ per a single 512 × 512 image frame. As such it is very suitable for integration with RF transmitter to form a compact, ultra low-power image processing system for WCE application.