• by Mark Walsh  @markfwal, December 16, 2011

After hitting an all-time high in October, the number of online videos viewed in November slipped from 42.6 billion to 40.9 billion in November, according to the latest comScore data. The total U.S. audience also declined--from 184 million to 183 million--as well as the average time spent watching video per viewer, from 21.1 hours to 20.5 hours monthly.

Thanks to YouTube, Google sites collectively had the largest audience in November, with 161 million unique viewers, each of whom racked up an average of 7.4 hours watching video. Given YouTube’s dominance, the battle in the online video rankings is really over second place, which music video powerhouse Vevo reclaimed from Facebook last month. 

While both sites’ audiences dipped from October, Vevo had 55.4 million viewers in November compared to 50.8 million for Facebook. That total put the social networking giant in a virtual tie for third place with Yahoo, with an audience of 50.4 million, up from 43.8 million in October. It's unclear whether that spike reflects the Web portal’s launch of a slate of women-focused video shows in November and its new content partnership with ABC News.

But the audience gain could bode well for Yahoo’s efforts to establish itself as more of a video hub, offering a range of original as well as syndicated material. Among the top 10 Web video properties, Yahoo was the only one to see a sizeable traffic increase in November. Rival portal AOL, by contrast, saw little change in its audience from the prior month, at 43.4 million. 

The falling total of videos viewed in November meant people also watched fewer ads overall: 7.2 billion compared to 7.5 billion in October. Hulu again generated the highest total of video ad impressions, with 1.3 billion, followed by Tremor Video (1.1 billion), and Adap.tv, which crossed the 1 billion mark for the first time. BrightRoll Video Network had 756 million impressions, Specific Media (512 million) and CBS Interactive (415 million).

Time spent watching video ads totaled more than 3.2 billion minutes, with Tremor delivering the highest duration, with 614 million minutes. Video ads reached more than half (53%) of the total U.S. population, an average of 47 times during the month. Hulu had the highest frequency of video ads, at an average of 44.