Streaming platform-player company Roku says its advertising sales performance had continuing strong results in the first three months of this year.

“Ad spending by major agency holding companies with Roku more than doubled. ... a really strong quarter for the advertising business,” said Scott Rosenberg, senior vice president/general manager, platform business at Roku, during the company’s Q1 earnings call with analysts on Thursday.

Roku does not break out ad revenue in its earnings reports. But it says in the first quarter, monetized video ad impressions more than doubled year-over-year. 

In addition, when looking at total TV streaming ad impressions -- sold by Roku or its publishers -- that number more than tripled.

Another indicator of advertising growth -- average revenue per user (ARPU) -- grew 32% versus a year ago to $32.14 in the period.

Nearly 60% of Roku's "platform" revenue -- where its software and technology reside on smart TV systems -- comes from advertising, according to analysts. In the first quarter, platform revenue was up 101% to $466.5 million.

In the fourth quarter of 2020, advertising revenue on Roku’s platform was estimated to be $265 million, according to MoffettNathanson Research -- or about 56% of total platform revenue, which Roku says was $471.2 million.

First quarter set-top-box revenue from the sale of players grew 22% to $107.7 million.

Company-wide, in the overall first quarter, Roku's revenue grew 79% to $574.2 million. Net income was $76.3 million versus a net loss of $54.6 million in the year-ago period.

Roku says its active accounts in the first quarter of 2020 were up 35% from a year ago to 53.6 million. It added 2.4 million accounts versus the fourth quarter of 2020.

First-quarter streaming hours increased by 1.4 billion hours over last quarter, to 18.3 billion.

Roku believes it can achieve strong growth, even against other digital media platforms. It touts estimates from eMarketer, saying that U.S. viewers on an average day will spend more time on TV streaming than all major social-media platforms combined.

While many analysts feel there is more upside to Roku, there is risk that some streaming direct-to-consumer content could find its way onto legacy pay TV bundles, says Jeff Wlodarczak, media analyst of Pivotal Research Group.

In addition, Wlodarczak says another concern is the big ad-free subscription video-on-demand services -- Netflix, Disney+ and HBO Max -- which could siphon away viewing time from ad-supported streaming services.