Americans are watching more TV on streaming video devices than ever, according to Conviva. The firm claims that total viewing hours across all streaming TV services surged 212% over the past 12 months, and six device families -- Roku, Amazon's (AMZN -0.29%) Fire TV, Sony's PlayStation, Microsoft's Xbox, Apple (AAPL 1.30%) TV, and Alphabet's (GOOGL -0.27%) (GOOG -0.28%) Google Chromecast -- dominated the market.

Graph showing share of U.S. streaming video hours for six devices in Q3

Data source: Conviva. Chart by author.

Conviva also reported that total video plays on streaming devices grew 292%, buoyed by a 145% increase in plays on connected TVs. Meanwhile, total plays on mobile devices grew 57% and fell 18% on PCs.

Those figures indicate that connected TVs are becoming a major platform, which explains why Amazon, Apple, and Google are expanding into the market. Connected TV devices also help the three tech giants grow their smart-home ecosystems, including smart speakers, hubs, and other connected devices.

However, that fertile market for tech companies could spell doom for traditional media networks and pay TV providers, which are struggling against the rise of cord-cutting across the country. This ongoing paradigm shift will force those aging companies to aggressively expand into the streaming TV market to stay relevant.