Shares of Internet audio and video technology company RealNetworks surged nearly 17% on Friday after investment firm Robertson Stephens upgraded the stock to a buy rating.

Move comes as execs of Seattle-based RealNetworks recently completed a European road show to tout to investors its subscription-based RealOne service. As of the end of the first quarter, RealOne had 600,000 subs who pay $10 a month for exclusive content.

RealPlayer clicks

Expected to help boost subscriptions in RealOne is RealNetworks’ latest version of RealPlayer, which improves the quality of video streamed on the Web and makes it comparable to television for high-speed Internet users.

The Robertson Stephens recommendation also follows Sony’s $10 million investment in RealNetworks last month under which RealOne will be included on Sony-branded hardware devices, including its vidgame console PlayStation 2.

Shares of RealNetworks closed up $1.31 to end Friday at $9.10. The stock traded 5.8 million shares, more than four times its average daily volume.