The closest thing to it that the cable-viewing masses have right now is so-called pay-per-view programming.
"The thing that stinks about pay-per-view is, you have to make an appointment" to see a scheduled movie, groused Ed Pardini, Philadelphia regional vice president for Comcast Corp.'s cable division.
Cable operators such as Comcast telecast recent movies and special events several times a day, and charge extra for them. But these schedules aren't always convenient to a viewer.
"Life gets in the way," said Paul Whitehead, vice president of strategic assessment for the cable industry standards body CableLabs.
Thus, on-demand TV could give consumers more flexibility in their telly-watching.
It isn't free, of course.
Comcast expects to charge $3.95 for relatively recent movie releases and $1.95 for so-called library titles, older movies and television programs. A few hundred titles will be available initially, the company said.
Comcast is testing its VOD offerings with 200 to 300 trial customers in Willow Grove and Lower Merion, and it expects to market the service commercially by the end of the year.
Using a remote control to flip through on-screen menus, Pardini showed how the system works by ordering Antitrust, the 2001 techno-thriller about a ruthless corporation's attempt to monopolize a breakthrough communications technology.
The movie began playing immediately.
"I own this movie for a full 24 hours," Pardini said.
As with a videocassette or DVD, customers can view an ordered movie as often as they want to during the 24-hour rental period. Unlike a rented video, there is nothing to return - and no late fees.
The version Comcast is testing features the same functions as a VCR: pause, fast-forward, rewind, and the ability to stop for several hours and pick up where you left off.
Each customer gets a private feed of a VOD movie from Comcast's remote video servers to the customer's home. A video server is a computer that handles, or "serves," requests to view movies by transmitting the video directly to a customer's cable box.
The server sends the movie as digitally encoded light pulses that travel over a fiber-optic network; unlike some other VOD systems, Comcast's does not transmit video over the Internet.
At the node - the point in the cable network where the fiber turns into coaxial cable - a device called a modulator translates the digital pulses into a video signal that can be understood by the cable box atop the customer's television.
As you relax on your sofa about to get comfy with, say, Hannibal, a computer program is busy checking your credit and processing the transaction.
"At the end of the day, the [cable operators] are looking for a return on their money," and it is the software's job to make sure space on the network is allocated efficiently, said Naresh Makhijani, vice president of engineering for DIVA Systems Corp., of Redwood City, Calif.
DIVA makes equipment and software for VOD systems used by AT&T Broadband and Charter Communications Inc., of St. Louis, among other companies.
The software acts as a bandwidth traffic cop, handing off network space as customers start and stop their VOD sessions, Makhijani said.
"It's also tying back to the billing system," sending instructions to put an additional charge on your next monthly cable statement, he added.
So what happens when everyone wants the same movie at once?
Technology advances have made it much more feasible for "server farms" - buildings crammed with electronics - to dole out movies on a scale that cable systems require, CableLabs' Whitehead said.
System operators also use probability theory to estimate how many customers to prepare for at any given time.
There are other offerings going by the VOD label, though the products have some key differences.
There's "near-VOD," a euphemism for the continual playing of movies starting every 15 to 30 minutes on pay-per-view channels.
And there's subscription video on demand, or SVOD, in which customers pay a fee, perhaps $4 extra per month, to access a library of special content whenever they want. For instance, the subscription service might appeal to an HBO customer who likes The Sopranos, but can't view it at its normally scheduled time.
Also, a recently announced venture by several big Hollywood studios will reportedly be transmitted via high-speed Internet connections, and viewed initially through subscribers' PCs.
Forrester Research Inc. has predicted that on-demand content will constitute 40 percent of cable viewers' television time by 2006, and generate $7.8 billion in additional revenue for cable system operators.
AOL Time Warner Inc. recently illustrated just how big a deal the new technology is by creating an entire interactive video division to push it forward.
AOL Time Warner chief executive officer Gerald M. Levin said creation of such services "was one of the top reasons" that America Online and Time Warner merged.
Levin predicted that, with the company's considerable clout and capabilities, it would bring interactive video services such as VOD to the mass market faster than any other firm.
It should be some race: Everybody in the video entertainment business is looking at VOD.
"Video on demand is something we know customers are very interested in," said Tracey Baumgartner, a spokeswoman for AT&T Broadband, the cable-TV division of AT&T Corp.
The service is fully operational for AT&T customers in Atlanta, and is being tested elsewhere.
"Initially, the feedback is that customers really like the added choice and added convenience," Baumgartner said.
Other cable operators, including Charter and Cox Communications Inc., the No. 4 and No. 5 cable firms, are also offering or testing VOD.
Not to be outdone - and seeking to outflank burgeoning online bootlegging of Hollywood hits - film studios including MGM, Paramount Pictures, Sony Pictures, Warner Brothers and Universal Pictures said this month that they, too, would soon have a movies-on-demand mechanism for consumers.
Blockbuster Inc., the top video rental chain, doesn't plan on getting left behind, either.
Earlier this year, Dallas-based Blockbuster wrapped up VOD trials in Salt Lake City, Seattle and Manhattan.
"Blockbuster continues to study and explore VOD, and we expect to be a force in the VOD arena," Randy Hargrove, a Blockbuster spokesman, said.
Hargrove suggested that the technology did not yet seem to pay for itself, but he added that Blockbuster would get more aggressive with providing VOD if and when an effective business model emerged.
That was a challenge, Comcast's Pardini conceded, but he said it was doable.
Akweli Parker's e-mail address is aparker@phillynews.com.
