The latest comScore Video Metrix has found that YouTube and Hulu are dominating the online video viewing minutes of US Internet users with the latter drawing nearly twice as many video ads as its nearest rival.

In all the Video Metrix for May 2011 service showed that 176 million US Internet users watched on average of 15.9 hours of online video content engaging in 5.662 billion viewing sessions during the month.

As ever, YouTube was the engine for the continued dominance of the Google Sites in online video, resulting in 147.2 million unique viewers, hugely ahead of second place online music video site VEVO with 60.4 million, Yahoo! with 55.5 million, with 48.2 million, then Viacom Digital with 46.5 million viewers.

When looked at in terms of viewing minutes, an essential element for monetisation, there was an interesting shift in the order showing the stickiness of compelling content.

Google broke the five-hour barrier with 311 minutes per viewer in the 2.17 billion sessions it claimed but second place in terns of minutes was the Hulu over the top (OTT) online video service with 217.8 minutes even though it only boasted 28.5 million unique users and just under 200 million viewing sessions.

VEVO was next some way behind with 105 minutes, the only other supplier to get into treble figures and then Viacom, home of MTV, was the only other to get above 50 minutes with 74.2.

Huluís strong performance was also indicated by its clear lead in terms of its business creation with the OTT service generating the highest number of video ad impressions, 1.3 billion, out of the total of 4.6 billion video ads viewed by Americans in May 2011. Tremor Media Video Network ranked second overall, highest among video ad networks, lagging some way behind with 700.8 million ad views, followed by (642 million) and BrightRoll Video Network (565 million).

More than 2.0 billion minutes were spent watching videos ads totalled with Hulu delivering the highest duration of video ads at 560 million minutes. Over four-fifths (83%) of the US Internet audience viewed online video. Video ads accounted for 12.6% of all videos viewed and 1.2% of all minutes spent viewing video online.