Get maximum pics with minimum bits
-- EDN, December 23, 1999
The SM2210 real-time codec from Stream Machine (Figure) supports simultaneous MPEG-2 encoding and decoding, allowing the device to perform time-shifting functions. ReplayTV's and Tivo's digital VCRs and ATI Technologies' Video Wonder PC add-in card popularized these functions (www.replaytv.com, www.tivo.com, www.ati.com). Stream Machine focused on achieving high image quality at bit rates as low as 2 Mbps, although the device supports variable bit rates as high as 10 Mbps and constant bit rates as high as 15 Mbps for IBP (intra, forward-predicted, branch-predicted) frames and 30 Mbps for I-only frames. Low-bit-rate encoding is key to maximizing recording time, which lower-density mass-storage devices, such as small hard drives and CD-Rs, require to hit consumer-electronics-friendly price points. Fortunately, analog television and small video frames on computer monitors also tend to be "forgiving" display devices.
D1-resolution NTSC video encoding requires only 4 Mbytes of external synchronous DRAM, the company claims, and the SM2210 supports glueless interfaces to NTSC- and PAL-video encoders and decoders, Universal Serial Bus-interface chips, PCI bridge chips, and embedded microcontrollers. You'll need to handle audio encoding and decoding elsewhere than in the $49 (4000) SM-2210, however, and figure out how to keep the audio and video time-synchronized. Stream Machine's chip is in production, and the company has also developed two reference designs: the $25,000 Symphony stand-alone personal video recorder and the $10,000 Insta-Replay video-capture and -playback PCI board for PC applications. Both reference designs include software and firmware, schematics, a bill of materials, Gerber files, and complete documentation.
Stream Machine, 1-408-435-9166, www.streammachine.com.
-by Brian Dipert
