LOS ANGELES -- A breakthrough in television advertising debuted without fanfare last spring as a brand-name box of crackers appeared on the CBS sitcom ''Yes, Dear" for about 20 seconds, seen but hardly noticed by millions of viewers.
Unbeknownst to them, the image of Kellogg's Club Crackers had been digitally painted onto the top of a coffee table after the scene was filmed, launching the latest advance in a marketing practice known in the industry as product placement but derided by critics as ''stealth advertising."
The ''Yes, Dear" episode in April 2005 marked the first commercial use of a patent-pending innovation dubbed Digital Brand Integration, or DBI, developed by New York-based Marathon Ventures, and grew out of an unprecedented marketing deal with CBS.
Since then, CBS has used the technology to plug brands such as StarKist Tuna and Chevrolet on several other shows, including the hit police drama ''CSI: Crime Scene Investigation" and new sitcom ''How I Met Your Mother."
David Brenner, founder and president of Marathon, said his company expects to unveil a new pact soon with the Fox network, a unit of News Corp. Ltd.
Blending brand names and products into television shows, as opposed to traditional ads that run during commercial breaks, has gained greater currency in recent years as the industry faces the rising popularity of TiVo and other devices that let viewers skip commercials.
But some industry experts suggest that product placement -- digital or otherwise -- has limited value in delivering a message.
The technology, pioneered by a New Jersey-based outfit called Princeton Video Image, has been a part of network sports broadcasts for nearly a decade.
Virtual product placement in scripted prime-time series dates back to a non-paid experiment conducted on the UPN network in March 1999, when images of several brands, including Coca-Cola and Blockbuster video, were digitally spliced into an episode of the now-defunct drama ''Seven Days."
Back then, network executives voiced skepticism about widespread use of the technology in scripted prime-time programs. Part of what was missing was a system that allowed the networks to easily market placement spots to advertisers.
The key component in the DBI system is a process for cataloging each frame of video in a TV episode to build a list of precise scenes and positions offering advertisers the best natural fit for their products. The idea is for digitally inserted images to be visible but not overly conspicuous.
''Although we want the product to be noticed, we don't ever want it to intrude on the creative process or the creative dynamic of the show," Brenner said.
Experts say striking that balance poses one of the greatest challenges to product placement.
''Simply placing a can of something, or a box of Wheaties on a table in the background . . . I'm not sure if that builds brand preference or brand loyalty, or if consumers, quite honestly, realize it's there," said David Cohen, interactive media director at advertising agency Universal McCann.
Conversely, Cohen said, ''The moment it starts reeking of overt product placement . . . is when it starts losing its effectiveness and its appeal."
Nielsen Media Research said network product placements in prime time last year numbered 108,261, up more than 30 percent from 2004. The trend has been most pronounced on reality series such as NBC's ''The Apprentice."