Millions of French couch potatoes who want to watch either “Questions pour un Champion” (Questions for a Champion) or “Rendez-vous en Terre Inconnue” (Encounter in an Unfamiliar Land), on France’s two biggest public TV channels this evening, may have to eat their dinners in front of the set.

Millions of others who opt for a film about a snowboarder who is killed in an avalanche, showing on Europe’s biggest commercial channel, TF1, will have 15 extra minutes to finish their meal.

The quarter-hour gap in prime-time kick-off times on France’s dominant television channels may not seem like much. But it belies a revolution-in-the-making on France’s audiovisual landscape. It's what you won't be seeing in those 15 minutes on the public broadcasters that is revolutionary for many French.

And that is advertising.

The prime-time shows on public channels France 2 and France 3 will start at 8:35 pm sharp, while “Avalanche”, over on TFI, starts to rumble at 8:50 pm.

As of tonight, France's public television stations - and there are five of them in all – will put into effect a new ban on all advertising between the hours of 8pm and 6am. By 2011, France plans to phase out all adverts from French public TV, 24 hours a day.

The official justification for the move is an attempt to create a high-quality public television service in France, along the lines of the much-admired BBC.

France's president, Nicolas Sarkozy, caused a lot of ruction when he announced his ambitions last January 8 as part of a much broader overhaul of France's sclerotic audiovisual landscape.

Sarkozy insists there are no ulterior motives here: he simply wants to deliver better televisual fare, with more cultural programming, and less commercially-driven drivel, as he sees it.

But beneath the patina of that shiny gloss lies a rougher surface.

Banning adverts on French television means the immediate loss of hundreds of millions of euros in sacrificed advertising revenue in the key prime-time slot.

That sacrificed revenue is estimated at 200 million to 380 million euros - money that will be redistributed elsewhere in the marketplace.

All of the media industry, and television is hardly an exception, have seen their ad revenues decline in the face of recession. Add to this the sudden flurry of new digital channels blossoming on the televisual landscape, and you have a recipe for very tough times ahead for mainstream broadcasters.

And here's where things get tricky. TFI, the private broadcasting behemoth that commands almost 60% of all of French television’s ad revenues, stands to gain from the sudden attrition in the market. Presumably, some of the advertisers dropped from public TV will migrate to TFI or other private rivals, such as the upstart M6.

Sarkozy, for his part, plays down such concerns. He says he plans to compensate the public broadcasters with 450 million euros in state aid, some of it to be gleaned from a new tax to be imposed on mobile phones and the Internet.

But the unions fear that these revenues will fall short, and that the public broadcasters are getting a raw deal.

And then there are those who see more sinister motives behind the move.

Critics see the whole thing as a ploy by Sarkozy to lavish largesse on his media-boss friends at the private networks. Defenders of Sarkozy’s reforms dismiss such charges. They say TFI itself is battling declining audiences, and the growth of digital broadcasting and suggest that the 450 million euros being provided in compensation to the public broadcasters is manna from heaven – a guaranteed source of revenue – at a time of plunging ad revenues.

But one major objection that won’t go away so easily stems from a clause in the new audiovisual code that would give the executive – that is, the president, the final say in who runs the public broadcasters.

This smacks to some of a return to the antediluvian days – just a few decades ago – when French television was state-controlled, with the editorial writ virtually coming straight from the Elysée Palace.

Some in the French media have darkly suggested that Sarkozy has finally achieved a life-long ambition: to become head of programming at a major TV network.