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MédiamétrieMédiamétrie is developing state-of-the-art methodologies and technologies for audience measurement. TV audience measurement is based on tagging the audio emitted by television channels – a technology known as audio watermarking. It is coordinated within Médiamétrie by a specialist team of audio-visual technicians and engineers.

Guaranteeing quality audience measurement

Médiamétrie has used watermarking as a television audience measurement technology since 2008. This technology involves the insertion of an inaudible tag – a tattoo – into the audio stream broadcast by television channels; this tag carries a unique identifier specific to each channel, as well as the time and date of the programme broadcast live or viewed as catch-up.

The tag is recognised by two types of audience meters. The first - a fixed audience meter - is a tablet installed in panellist households beside each measured television set. The second is a small smart meter worn by the panellists as a wrist bracelet or belt clip whilst they are at home, away from home or on the move. This equipment allows Médiamétrie to identify which channel the panellist is watching - key data for calculating audience figures. Médiamétrie is recognised worldwide for its innovations in audience measurement.

Jérôme Méric, Director of Measurement Systems Development at Médiamétrie, explained further: "The watermark is inserted into the sound spectrum without altering the programme audio. All broadcast streams are tagged using watermarking, so it is possible to count and identify instances of live broadcast, time-shifted and catch-up viewing, regardless of the access network (DTT, Sat, IPTV, OTT, HbbTV) or the screen used."

To ensure high-quality measurement and to collect all audiences, the challenge is to keep the tag from being altered, so that it will always be recognised by the meter. At Médiamétrie, the TV & Radio Engineering division is in charge of this activity. This team of three work under the Measurement Systems Department. Nelsy Zami, TV & Radio Engineering Manager, explained: "For this role, you need knowledge of the technology used in broadcast control rooms, their equipment, and architectures, etc."

Insertion into the architecture of each television channel

Médiamétrie's TV & Radio Engineering division aims to help channels set up and operationally maintain the watermarking of their broadcasts. In order to ensure that the tattoo is always present, Médiamétrie chose a watermarking technology developed by Kantar, as it was the most resistant to the acoustic path.

Médiamétrie teams agree with the television channels where to insert the watermark in their broadcasting architecture. They help ensure it is deployed correctly. The method for inserting this watermark differs between channels according to their solutions and broadcast technologies. Médiamétrie will proceed to check that the installation used by the channels conforms with TV audience measurement specifications.

Once the watermark is in place, Médiamétrie must ensure that it always remains. A supervision process exists to that end. This involves checking the broadcast signal for the watermark in order to detect any anomalies. This process must be set up by the channels themselves. As a trusted third party, Médiamétrie also implemented this process at the same time via monitoring stations operated by technical partners which specialise in this field (TDF & Witbe).

Technological developments, for example the growth in cloud computing, require the methodologies and technologies used to be regularly updated. Watermarking technology is also evolving in directions that the channels and Médiamétrie must take into account.

According to Nelsy Zami, "One challenge we face is how to adapt the technique to all media players, regardless of their size and infrastructure."

Close cooperation with TV channels

Setting up watermarking requires close cooperation between Médiamétrie and the technical departments of its customers. They are trained and supported by Médiamétrie’s teams as regards the insertion and operation of watermarking so that they can master the technology.

"Our task is to offer instruction in the technology and share experiences, especially for our new contacts in the control rooms," said Nelsy Zami.

Such expertise soon becomes indispensable as the complexity of broadcasting and audience measurement technologies increases.

Laure Osmanian Molinero