The phenomenon in question is called the Hitlergruß (Hitler Greeting) and the link is the 2001 drama Conspiracy, a film about the Wannsee Conference of 1942.

The dictatorship mandated the use of the Hitlergruß and its salute for all German civil servants in 1933 as a substitute for older greetings like Guten Morgen/Tag (good morning/day) or grüß Gott (there is not a decent translation for it in English, but it was more common in Catholic areas of southern Germany and Austria). The Hitlergruß was not mandatory for non-civil servants but there was a strong pressure for Germans to use it. Conversely, there were laws prohibiting Jews from using the Hitlergruß.

Now how common was the Hitlergruß is difficult to parse out. Certainly, civil servants did employ it. But the traditional greetings did not go away either. It was not uncommon for Germans to use the Hitlergruß in formal settings or among strangers but lapse into traditional greetings among family, friends, and colleagues. Outside observers such as the German Jew Victor Klemperer noted that the use of the Hitlergruß ebbed and flowed with the wider fortunes of the dictatorship. His diary recorded in September 1941 that while the shopkeepers and patrons at one bakery barely used the Hitlergruß, another used it exclusively.

The historian Peter Fritzsche notes the ambiguity of the Hitlergruß in his book Life and Death in the Third Reich and is worth quoting at length:

"Heil Hitler!” illustrates both the coerced and self-assertive aspects of the national revolution in January 1933. It raises questions about the illusory nature of acclamation: since once everyone said “Heil Hitler!” the greeting no longer reliably indicated support for the regime. But much of the power of Nazism rested on the appearance of unanimity, which overwhelmed nonbelievers and prompted them to scrutinize their own reservations. Each raised arm undermined a little bit the ambiguous relations among neighbors and built up a little more the new racial collective of National Socialism. Did that mean that sympathies for Nazism had diminished when more people once again called out “Good afternoon” on a Berlin street? Like Klemperer, historians are still counting the “Heil Hitlers” outside Zscheischler’s bakery in Dresden and are still figuring out what it meant when customers said “Good afternoon” instead.

Circling back to Conspiracy, it is highly likely that the film's various "Heil Hitler!"s are accurate. The attendees of the conference were high-ranking state officials and members of the NSDAP. However, the linked clip does not include the scene where the chairman of the Wannsee Conference, Reinhard Heydrich, proposes temporarily dispensing with the Hitlergruß otherwise the attendees would be saluting all day and not getting down to business.