Digital Cameras
Overview
Digital cameras, also called DSC (digital still cameras), have eclipsed silver halide photography, even in many professional applications. Convenience is king and the ability to shoot in low light situations using electronic sensors instead of chemical emulsion film are two very compelling advantages. Camera phones bolster the overall digital imaging market and impact the strict definition of the DSC market as miniature sensors and lenses continue to improve.
Challenges
Digital cameras perform many computations beyond just compressing the captured image. This includes auto-focus, aperture and speed selection based on various light metering schemes, as well as possible lens distortion corrections. Panorama stitching is possible in some cameras. Other functions include special color effects and white color balancing, as well as color space conversions. The camera may also draw the date/time from the real-time clock (RTC) onto the image. Today, many DSC cameras will also include a video capturing function using MJPEG, MPEG-4 or H.264 compression. This requires audio capture and encapsulation into popular PC media containers. The menu graphics, font rending, USB interface and battery charge monitoring require additional processing horsepower. The list of demands is long and battery lifetime is critical.
MIPS Solution
A large percentage of DSC devices today are MIPS-BasedTM. Samsung introduced the world's first HDMI-enabled digital camera based on MIPS. Zoran, Toshiba, NEC, Sunplus, LSI Logic and others supply the DSC market with MIPS-Based ICs. OEMs include Canon, Samsung, JVC, Pentax, Casio, Minolta and Fujifilm. Several digital camcorders also use MIPS-Based ICs.
MIPS Pro Series® cores include the CorExtendTM capability that allows system designers to extend the functionality of the MIPS architecture, letting them define and add instructions that operate on data in the general-purpose registers in the same manner as standard MIPS instructions. While many digital cameras have used a combination of DSP and RISC cores for image processing, CorExtend can reduce the two cores down to one, saving die size and battery life. For those implementing JPEG baseline decoding fully in software, an application note is available that leverages programming tricks to reduce the cycle count of the publicly-available code from the Independent JPEG Group (www.ijg.org).
