Mediaset, controlled by the family of former Italian Prime Minister Silvio Berlusconi, has been embroiled in a multi-billion-euro legal dispute with Vivendi since a collapsed pay-TV deal in 2016.
Vivendi holds 29% of the Italian broadcaster, a stake it built after walking away from the purchase of pay-TV unit Mediaset Premium and which Mediaset considers hostile.
The telephone call between Mediaset CEO Pier Silvio Berlusconi and Vivendi CEO Arnaud de Puyfontaine was cordial, the source said, and could be a first step towards exploring a deal.
"We can find a solution with Vivendi ... in the best interest of the shareholders of Mediaset", Chief Financial Officer Marco Giordani told analysts earlier on Wednesday in a call on Mediaset's first-half results.
The potential breakthrough comes after the European Union's top court last week ruled against an Italian law that forced Vivendi to freeze two thirds of its Mediaset stake due to its parallel holding in Telecom Italia.
That victory for Vivendi, together with its success in blocking plans by Mediaset to create a Dutch holding company to pursue tie-ups with peers in Europe, could boost the chances of a compromise deal, analysts say.
Mediaset shares have gained up to 20% since the European court ruling boosted the prospect of a deal with Vivendi. The stock ended up 2% at 1.88 euros on Wednesday, erasing early losses after Giordani's remarks.
Efforts to end the row have failed so far, with Mediaset reluctant to drop its damage claims as requested by Vivendi, which soon might regain its voting rights on its full stake in the Italian broadcaster.
"If there are projects, ideas that create value, we are and will be available to discuss them," Giordani said.
He said Mediaset's European growth strategy remained valid and the group would seek ways to rethink the project once markets stabilised.
The COVID-19 pandemic has increased pressure on Mediaset and other traditional broadcasters in Europe, which were already suffering due to stiff competition from streaming services like Netflix and web giants like Google.
Mediaset posted a net loss of 19 million euros (17.25 million pounds) in the first half as the pandemic prompted companies to slash spending on advertising despite soaring viewership.
Revenues fell by a fifth, driving operating profit down 83%.
Ad spending recovered in July-August and results should improve in the second half barring another lockdown, Mediaset said.
However, it warned that visibility was too low to provide any medium-term guidance and said the market situation remained "extremely fragile".
By Elvira Pollina