Record heights for content viewing have been recorded by the VEVO music online video service according to the comScore US online video rankings for April 2011.

In all, the latest comScore Video Metrix showed that 172 million U.S. Internet users spent an average of 14.9 hours watching online vide, engaging in more than 5.1 billion viewing sessions during the course of the month. This represented a slight dip in the ranking compared with March 2011 where 174 million users watched 5.7 billion viewing sessions.

As ever, driven by, Google sites dominated the online video rankings with 142.7 million unique viewers, more than 1.9 billion viewing sessions, and highest time spent per viewer at 286 minutes. Behind by some way was VEVO with 55.2 million viewers but the online video music service’s viewership reached record levels in April, crossing the 300 million viewing sessions mark and averaging 1.7 hours per viewer.

Following VEVO was and Yahoo! Sites with 53.2 million viewers; with 46.7 million viewers; Microsoft, 46.5 million viewers. In March 2011, the ranking behind Google was AOL, Yahoo!, Microsoft, VEVO then Facebook.

As an indication of how the business of online video is taking shape, 81.9% of the US Internet audience viewed online video, served with 3.8 billion video ads in April 2011. The duration of the average online video ad was 0.4 minutes, whereas the average online content video was 5.2 minutes. Video ads accounted for 11.6% of all videos viewed and 1.1% of all minutes spent viewing video online.

Subscription and ad-funded OTT service Hulu generated the highest number of video ad impressions at more than 1.1 billion; Tremor Media Video Network ranked second overall (and highest among video ad networks) with 603.2 million ad views, followed by (601 million) and BrightRoll Video Network (460 million).

Time spent watching videos ads neared 1.7 billion minutes during the month, with Hulu delivering the highest duration of video ads at 470 million minutes. Video ads reached 42% of the total U.S. population an average of 30 times during the month. Hulu also delivered the highest frequency of video ads to its viewers with an average of 45 over the course of the month.
The leading video ad networks in terms of their potential reach of the total US population were: Tremor Media at 47.1%, BrightRoll Video Network at 40.1% and Break Media at 39.1%