This post is by Andy Mitchell, European MD at BrightRoll.

The digital video ad industry is awash with debate around viewability and measurement.

Traditionally, digital video advertising has been transacted based on models such as cost per engagement (CPE), cost per view (CPV) or cost per thousand (CPM). Understandably, most advertisers assume the ads they run are viewable by the audiences they are paying to reach. However, there is substantial evidence that this is not always the case.

This has left a number of pressing questions still percolating in the video advertising industry. How do we know an ad is being viewed by the intended target audience? How is viewability measured? And how accurate is the measurement available in the industry today? As video ads continue to soar in popularity with brands, it is paramount that these questions are answered.

Although viewability measurement is still a complex process (including the diverse range of browsers and publisher web page configurations in the marketplace), recent advancements in technology have enabled advertisers to more accurately measure whether ads served are seen by users.

On top of this, the digital advertising industry is increasingly moving toward a "viewable" impression standard, whereby impressions are measured and counted based on the opportunity for users to see ads. In March, the IAB and MRC "Making Measurement Make Sense" (3MS) initiative officially proposed a viewable impression standard for the industry, defining a viewable video impression as: 50 percent of an ad's pixels must be on an in-focus browser tab in the viewable space of the browser page for two consecutive seconds.

Ultimately, the impact of this for advertisers is that viewability now sits alongside other existing metrics as an increasingly important way of measuring campaign performance. This in turn means that it's crucial for advertisers to be aware of the strengths and weaknesses of the measurement options available to them in the market.

These options were discussed in a recent study by BrightRoll and Kellogg, which found significant variability in the accuracy, efficacy and reporting capabilities among different video viewability measurement vendors in the market.

The study highlights a number of key insights for advertisers. Chief among these is that independent, third-party measurement is the preferred way in which to ensure measurement free of conflict of interest.

On top of this, the study finds that reporting standards vary wildly among measurement vendors and there is a major discrepancy around compatibility. For example, not all vendors offer automated reporting that is in tune with new technology such as programmatic optimisation.

Finally, the report recommends that for any viewability solution to be effective it must be fully embedded in the advertisers' ad-buying system. This ensures that data is accessible on a real-time basis so that brands can optimise against it and make actionable decisions based on the results.

There is little doubt that the video ad industry is changing rapidly and gaining popularity among advertisers looking to reach audience across digital screens and traditional television.

But for this stellar growth to continue and the industry to realise its full potential, this growth needs to be underpinned by an industry-wide measurement standard. This will ensure that advertising money earmarked for digital video doesn't go elsewhere.