TWENTY-FIVE years ago this month a few thousand late-night cable-TV watchers in northern New Jersey witnessed the start of a revolution in music and television.

Over a crunching guitar riff, doctored footage of the Apollo 11 moon landing showed an astronaut planting a flag that read MTV. “Ladies and gentlemen, rock’n’roll!” proclaimed the announcer.

MTV was radio for the video age, with “video jockeys” instead of DJs and non-stop music. The channel’s first two songs were The Buggles’ Video Killed the Radio Star and Pat Benatar’s You Better Run. It sounded like a statement of intent. The MTV generation was born.

A quarter of a century later, the music channel has come a long way. At the end of this month at the Radio City Music Hall in New York, MTV’s Video Music Awards will be broadcast live to a potential audience of 1.3 billion in the 481m households around the world that take the channel and its offshoots.

There is unlikely to be much mention of the birthday. Like nominees Christina Aguilera and Shakira, most of the channel’s audience are too young to remember the world before MTV. The channel’s average viewer is 20 years old. But that doesn’t mean the network isn’t feeling its age.

Along with the launch of CNN, MTV ended the domination of major TV networks in America and was the fuse that lit the explosion of multi- channel television across the globe, according to Robert Thompson, director at the Center for the Study of Popular Television at Syracuse University, New York State.

Over the years it has changed constantly to keep up with its young, fickle audience while alienating the previous generation of viewers. MTV was once famous for premiering videos such as Michael Jackson’s Thriller or Madonna’s Like a Virgin, but now music videos have all but disappeared from MTV’s main channel.

Its most watched programmes are reality shows such as The Osbournes, Laguna Beach and The Real World. MTV has also fractured into a network of channels catering to an ever more demanding and distracted audience.

Owned by the media conglomerate Viacom and now part of MTV Networks, the channel’s stablemates include the VH1 music video channel and Nickelodeon, the children’s channel. Viacom also owns the Paramount Pictures studio but MTV Networks accounts for 85% of its operating profits.

MTV attracts huge audiences and makes big money. Ten days ago Viacom announced that it had made a profit of $416m (£219m) in the past three months, backed by strong advertising sales at MTV Networks.

But its audience is being drawn away by the internet, and advertisers are following the drift. In May the company announced a 10% decline in profit, due in part to the loss of a big — so far unnamed — advertiser in Germany.

MTV spawned a legion of imitators but today its biggest battle is online. Video threatened to kill the radio star, now the internet threatens MTV.

MySpace, You Tube, Google Video, Apple’s iTunes — MTV’s online rivals — are now eating up hours that teens and twentysomethings once spent watching television. As broadband penetration increases, that trend is likely to grow. There are now 9m homes in Britain with high-speed internet access and more and more households are getting wired every month.

Times Recommends

• C&G axed - 1,660 jobs to be lost
• UK house prices rise 1.1% as buyers return
• Mixed reaction to US banks repaying bailouts