For close to a decade-or longer, depending on how you count-the digital still camera (DSC) and video camcorder have evolved along distinctly different paths. Enter the GR-DV3000 digital video camera from JVC, one of many in an emerging breed of hybrid still/video digital image-capture devices hoping to scoop up sales by satisfying two consumer imaging needs at once.
Capable of capturing mega-pixel stills and electronically stabilized video through the fast 10x optical-zoom lens, the JVC unit sports both an electronic liquid-crystal display viewfinder and a sizable 3.5-inch swing-out LCD, allowing users to enjoy playback of their video masterpieces. The camera also captures four modes of JPEG-compatible still images and two modes of MPEG-4-compatible video to the Secure Digital (SD) memory card, Mini DV cassette or both.
All things imaging start off in the analog world, and a 2/3-inch-format Sony charge-coupled-device image sensor, the ICX286, combined with a Sony CCD CDX3602 timing controller, deliver a brigade of low-level analog signals for sensor readout-specifically, color and intensity values for each pixel. This pixel stream is subsequently fed to a Renesas HD49334 analog image processor, which controls noise through correlated double sampling of each pixel, boosts signal levels in a programmable-gain amplifier and converts the preprocessed signal into a 10-bit data stream with its internal A/D converter.
From here, the camera design splits the digitized imager output into separate streams to feed independent signal-processing engines for video and stills downstream.
Starting with the still-image capture path, a Texas Instruments DSP, the TMX320DSC24-combined with Spansion NOR flash and Hynix SDRAM at 2 Mbytes and 8 Mbytes respectively-handles digital still camera chores, with the TI part performing all the necessary demosaicing, color balance and JPEG compression on acquired images. The TI chip and companion memory parts all reside on a standalone circuit board. The board also supports a Philips ISP1181 USB controller for external interface to a host PC, and a Panasonic MN5772 for managing storage to the SD memory, which is used to store captured stills.
Looking at the video recorder portion of the system, a mix of microprocessors and a semicustom macrocell device handle video image processing. Because motion video does not require the 1.3-Megapixel native image resolution of the Sony image sensor, the processed/digitized output of the Renesas analog front end is presumably downconverted to more-appropriate video resolution for motion capture.
JVC's design combines downsampled video with the associated audio stream and ports them through a Sony-manufactured read/write head front end (CXA3521) on the cassette interface board, to format streams for tape recording. On record or playback, the camera can also take Mini-DV-formatted content and generate MPEG-4 for storage of video clips to the SD card, likely a second task for the TI DSP found in the design.
Digital ASICs in the GR-DV3000 do a formidable signal-processing job to ensure image stabilization. The ASICs must track and subframe the subject of interest to keep it "still," while shake at the long 10x zoom of the design is eliminated electronically.
The many optomechatronic elements of the design-lenses, tape transports, shutter/iris mechanisms and the like-all require analog finesse within a digital control loop. An NEC stepper motor driver, the microPD16879, orchestrates movement of the nine glass elements in four groups to affect zoom and focus of the optical train. Control of capstan, read/write and transport motors in the Mini DV assembly is handled with a Rohm analog controller, the BD6630KV, which is also on the same board as the Sony-manufactured read/write front end.
Along with myriad power-management components, other key analog audio ICs in the system include two AKM codec chips (AK4550), a Rohm BU2501FV D/A converter and a Sanyo audio interface.
Each of the product's two displays requires a set of supporting components, including two CXA3503 LCD driver/timing chips from Sony on a separate display board. Back on the main board, the JCP8405 component from Sanyo and one from Fujitsu, the MB90097, tackle display controller functions and the overlay of on-screen text information and icons.
Numerous components, subasssemblies and mechanical elements of the system are not shown in the diagram here, but make no mistake, total component count and electronics complexity in the GR-DV3000 are quite high-consistent with the somewhat disintegrated nature of the camcorder-DSC combo design. With a total of 12 high-density circuit boards in the JVC design, semiconductors from digital ASICs to small-scale analog and everything in between play a role.
Two-pronged market
Overall, the GR-DV3000 represents one of two prongs in the motion/still combo battle, coming at the market with a distinctively camcorder-centric design that happens to support stills with dedicated circuitry and extra available resolution.
The other angle that is playing out in hybrid design centers on the addition of motion capture to products that begin life as digital still cameras-a feat increasingly possible thanks to the availability of cheap, deep storage.
Given the size constraints most people put on their idea of a still camera, it seems that the addition of video to a DSC, with hard drive or high-capacity memory card storage, is likely to win the battle. On the other hand, consumers may be quite happy with separate lower-priced products that are optimized for respective imaging markets. Convergence may be a buzzword of the industry, but consumer buying patterns still support the popularity of single-function products.
By David Carey, president of Portelligent (www.teardown.com). The Austin, Texas, company produces teardown reports and related industry research on wireless, mobile and personal electronics.
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