News and New Products

Chips smooth out digital-video speed bumps

By Brian Dipert -- EDN, 10/14/2004

Eventually, all of the video-encoding, -decoding, and -display equipment in folks’ homes will interconnect via loss-free, copy-protected digital schemes, such as FireWire and HDMI (High Definition Multimedia Interface). A near-term scan of most living rooms, dens, and closets, however, will reveal lots of analog-interface gear: camcorders, DVD players and recorders, game consoles, set-top boxes, TVs, and the like. Video decoders, which convert from analog to digital, are the bridge from the analog present to the digital future, and Techwell’s $8 (10,000) TW9918 exemplifies today’s state-of-the-art technology in this arena.

The TW9918 accepts composite, S-Video, component, and SCART (Syndicat des Constructeurs d'Appareils Radiorécepteurs et Téléviseurs) video-analog inputs in various combinations, and its six 9-bit A/D converters with analog clamping circuits translate them into a VMI 1.4-compatible 4:2:2 YcbCr digital output over an 8- or 16-bit, ITU-R 601 or ITU-R 656 datapath. It automatically detects NTSC, PAL, or SECAM formats, and it provides a 3-D adaptive comb filter for NTSC (its primary advancement over Techwell’s earlier video decoders, which relied exclusively on a 2-D comb filter) (see “A crash course in color conversion,” EDN, June 7, 2001, pg 46). Other TW9918 features include a 4-H (four-horizontal-delay), 2-D comb filter for PAL; a multitap, polyphase-decimation-filter-based down-scaler; image-enhancement features, such as 2-D peaking control, 3-D noise reduction, and color-transient improvement; and synchronization circuitry for stable pictures with nonstandard video signals, such as with VCR fast-forward, rewind, and pause operations. The 3.3V part, which has 5V-tolerant I/O buffers, comes in a 128-pin LQFP and is now in production.

Once your video is in the digital domain, your compatibility struggles aren’t necessarily over. What happens if your video-output device supports MPEG-1, and its matching video-input counterpart speaks only MPEG-2 or MPEG-4? If your wired or wireless interconnect channel has a limited bit rate, either on an ongoing basis or temporarily due to interference, or if your storage media has limited capacity? What if the video output requires down-scaling before display or further processing?

ViXS’ XCode II streaming-video processors, which support both MPEG audio and video, can help. They upconvert MPEG-1 to MPEG-2 and MPEG-1 and MPEG-2 to either MPEG-4 simple or advanced simple profiles. They can also convert between elementary, program, and transport-stream layers and between variable- and constant-bit-rate formats; handle deinterlacing and telecine—that is, film-mode—and inverse-telecine functions, and, like the Techwell part, they support 3-D motion-adaptive comb filtering.

ViXs a year ago unveiled the initial $35 (10,000) XCode II processor, which can simultaneously output four video streams. The company now follows with the dual-stream, $25 XCode II-L; the low-power, dual-stream, $25 XCode II-N; and the single-stream, $20 XCode II-E. The company also offers a wireless point-to-point client/server reference design, a dual-tuner PCI add-in-card reference design, and a software-development kit.

Techwell, 1-408-435-3888, www.techwellinc.com.

ViXS, 1-416-646-2000, www.vixs.com.