By any measure, video is commanding an ever-greater share of online ad dollars. eMarketer, for one, expects video ad spending to increase by 40%, this year, to reach $3.1 billion.

But, how are marketing execs allocating all that money?

A clear majority, 64%, said they plan to include smartphones in their spend, while more than 50% said they are likely to include tablets, according to new research from BrightRoll. A smaller share, 30%, said they are likely to include connected TV.

While BrightRoll’s 2011 survey revealed that video had become a staple of online ad buys, this year’s survey shows that advertisers are embracing the viability of a new digital video viewerscape across four unique screens: computers, smartphones, tablets and connected TVs.

The findings, according to BrightRoll CEO Tod Sacerdoti, also indicated that budget allocations may be based on the “maturity curve” — or how long video has been available on each screen, instead of analyzing what medium is most effective in achieving campaign goals.

Overall, the report indicated that 30% of respondents expect online video to have the largest increase in media spending this year.

On the growth front, 70% of respondents said that clearer ROI and better success metrics are still needed to increase digital video ad spending.

Showing just how far the medium has come, however, 64% of advertisers said that online video is an equally or more effective medium than TV. Respondents overwhelmingly selected targeting — 43% — as what their clients deem the most valuable aspect of online video, followed by reach: 28%.

More than half of respondents said they are more inclined to buy online video inventory from a network or exchange than anywhere else — that’s a 20% increase from last year’s survey. Also of note, behavioral targeting remains valuable to advertisers with 64% of respondents indicating their online video ads will be behaviorally targeted in 2012 — a 14% increase from 2011.

However, only 5% of respondents said GRP is the most important success metric, while 18% said they are most interested in seeing additional research on GRP measurement for online video buying.