Kallasvuo was replaced at Nokia in 2010 by Stephen Elop after the Finnish group struggled to keep pace with smartphone rivals such as Apple Inc and those based on Android software.
"The operating system market for set-top boxes and IPTV (internet protocol television) is extremely fragmented. Each set-box manufacturer has its own software," he told Reuters on Thursday.
"What Zenterio can offer is a hardware-independent solution for pay-TV operators ... We are talking to many, many top-tier operators globally," he added.
Kallasvuo gave no details of the talks or targets for a company which last year had revenue of less than 100 million crowns ($15.4 million) and which has been developing its software for many years.
But he said 200 million set-top boxes were sold annually and that the company took license fees for its operating system, which is based on the Linux standard.
"The growth targets of course are quite high, it is a small company and a big market," he added.
Kallasvuo bowed out of Nokia in 2010 but said he had kept an eye on the company. He declined to express any opinions about the way Nokia is being run by Elop, whose strategy has been to launch mobile phones with software from Microsoft Corp, his former employer.