Speaking to a group of top British TV executives who were not sure whether to regard Yahoo as friend or foe, Semel urged them to index their dormant archives and add them to Yahoo's video search service.
"Video search is a way to monetize some of the stuff that's lounging around in warehouses and hasn't made a dime for years," he said at the Royal Television Society conference in England.
Yahoo and its rivalare each negotiating for the rights to a wide range of , but have been reluctant to give up control or lose out on advertising revenue. The BBC has promised to open up its own massive archive.
Yahoo has worked alongside television networks to promote shows like "America's Top Model" with sneak peeks and dedicated Web pages. Semel said that the company hopes to go further, and urged independent producers to think of Yahoo as an outlet for new programming.
"I don't think that Yahoo or any other Internet company should try to become a television network," Semel added. "We will be nowhere if we have to create our own content."
He warned TV executives that television would lose an increasingly large slice of the advertising pie in coming years due to fragmenting audiences and the prevalence of ad-skipping technologies--especially since consumers were spending more and more time on their computers.
"Where audiences go, advertisers tend to follow," he said.
On the sidelines of the conference Semel told Reuters that e-commerce giant eBay, which already competes with Yahoo in auctions, could become a rival in communications services, after its acquisition of Internet telephony firm Skype this week.
"Clearly they're going into communications. Whether they're going to be a threat, it's too soon to tell," he said.