Sustainability Of Streaming: How Does OTT Compare With OTA? - Part 2

Part 1 of this series began the analysis of the report by the UK’s Ofcom that compares the UK’s energy consumption in 2021 for content delivered and viewed in DTT (Digital Terrestrial Television) versus OTT (Over The Top) ecosystems. In Part 2, we dig further into the detail and imagine an OTT-only future.

From Energy Consumed To Greenhouse Gas Emissions

Converting energy consumed into greenhouse gas emissions (to be referred to as CO2e or Carbon Dioxide Equivalent) in the Ofcom / Carnstone report published in 2022 used the UK’s official multiplier of average CO2e emissions from energy generation for 2021. By combining the Greenhouse Gas intensity of electricity generation, the electricity grid transmission and distribution losses, and the well-to-tank emissions from upstream electricity production, the overall multiplier of 0.29130 was used to calculate the CO2e impact of DTT and OTT, giving the following result shown in Figure 1. 

Figure 1: Greenhouse Gas emissions per device hour (source: Carnstone / Ofcom 2022).

Figure 1: Greenhouse Gas emissions per device hour (source: Carnstone / Ofcom 2022).

Digging Into Detail

Inside the above headlines there are important details to discuss about what this all means for reducing energy consumption and therefore reducing CO2e in DTT and OTT environments.

From a Viewing Device efficiency perspective, OTT is considered more efficient than DTT because a percentage of OTT viewing takes place on smaller, much less power-hungry devices. A Smartphone, for example, is calculated in the Carnstone report as using 1W, compared to a regular television that uses 65.6W, or a SmartTV that uses 100W (note that these TV figures are averages for the UK based on the range of different-sized TVs installed).

From a Delivery Equipment efficiency perspective, the position is reversed. The Delivery Equipment chain begins with the data centers and networks used to transport the content and ends in the home with a mix of broadband or broadcast equipment to deliver the content to the final viewing device. In general, there is a more complex set of equipment required to deliver OTT than DTT which causes the higher level of energy consumption and CO2e. This is really where we need to unpick the details. Please refer to Article 1, Figure 1 for a diagram of the DTT and OTT components.

Working backwards from the Consumer Premises Equipment (CPE), in OTT we use Routers (average consumption of 10.5W) to deliver broadband to our devices. Some houses may also have mesh networks (6.5W) or network extenders (6W). In DTT, some households use Antenna Amplifiers (3W) to extend the signal reach.

In both DTT and OTT, many video services are delivered via STBs (set-top boxes) that add to the power consumption in the delivery chain. Some households access DTT services via a STB, others do so directly via the television itself. In the Carnstone report, a complex STB uses 18W. Obviously, a delivery chain without a STB doesn’t consume any of this energy.

The delivery network component includes data centers and CDNs for OTT, and transmitters for DTT. For OTT in the UK, as in most countries, there is a long list of CDN service providers, data center operators, and telecommunication service providers, providing shared use infrastructure. Arqiva is the UK’s broadcast network operator, with over 1100 transmitter sites throughout the country for broadcasting television and radio signals. Again, many countries have similar broadcast network structures. The Carnstone report calculated the following Wh per device viewing hour for each content distribution method.

Figure 2: Breakdown of Watt Hours per Device Viewing Hour by Delivery Equipment component (source: Carnstone / Ofcom 2022).

Figure 2: Breakdown of Watt Hours per Device Viewing Hour by Delivery Equipment component (source: Carnstone / Ofcom 2022).

The reason why OTT is less energy-efficient than DTT is almost equally distributed between these three delivery equipment components. But before we start finalizing conclusions, we need to clarify two key points.

First, the Carnstone study reports that total energy consumed in the UK in 2021 from DTT and OTT viewing was 4300 GWh (see Figure 3 and Figure 4 below). While there is over a 4x difference in energy consumption between the delivery equipment components (Figure 3), the energy consumption between OTT and DTT methods is almost level when the viewing devices are considered (Figure 4). This is due to both the higher number of hours viewed on DTT compared to OTT, and the lower energy consumption per hour of mobile devices used for an estimated 25% of OTT viewing. In absolute terms, the DTT distribution method consumed just 4.5% less energy than OTT in the UK in 2021.

Second, the analysis of OTT in this study is heavily based on VOD viewership, which involves duplicating and storing content in multiple locations throughout the distribution networks. A VOD-heavy approach hides the fact that watching Live content does not require the same amount of storage usage, which drives less energy consumption from the CDN infrastructure. As Live streaming grows (leading broadcasters are currently reporting a 70:30 VOD-to-Live ratio for streamed delivery), so the analysis of the energy usage associated with each use case will need to be updated.

Figure 3: Total UK Annual Energy Consumption for Video Delivery, broken down by Delivery Equipment system component (source: Carnstone / Ofcom 2022).

Figure 3: Total UK Annual Energy Consumption for Video Delivery, broken down by Delivery Equipment system component (source: Carnstone / Ofcom 2022).

Figure 4: Total UK Annual Energy Consumption for Video Delivery, including the viewing devices, broken down by Delivery Equipment system component (source: Carnstone / Ofcom 2022).

Figure 4: Total UK Annual Energy Consumption for Video Delivery, including the viewing devices, broken down by Delivery Equipment system component (source: Carnstone / Ofcom 2022).

Aiming For An Absolute Reduction In Energy Consumption

The subject of CO2e impact, and how the networks that are used for media delivery consume renewable vs. non-renewable energy, is obviously important. Without exception, the major UK broadcasters and network operators are using sources of renewable energy. But the enlightened thinkers who are trying to solve the problem of continuing to provide media services while also taking proper care of our planet are focused on finding ways to reduce the absolute levels of energy consumption, not simply run all infrastructure from renewable sources.

The OTT delivery components – SmartTVs, Mesh Networks, WiFi extenders, Home Routers, CDNs and Telco networks – need close inspection to ensure maximum efficiency as OTT consumption scales up. In the DTT chain the Transmitters need the closest inspection to minimize power consumption as DTT viewing decreases. The thinking underway looks at how we can completely stop consuming energy in as many areas as feasible. For example, should we stop using STBs in order to reduce overall energy consumption? Should we only have OTT and close down DTT? These are radical steps, and it is fair to say that we can only significantly reduce absolute energy consumption completely with some difficult choices. But in the areas that will certainly need to continue, what do we need to do to dramatically reduce total energy usage?

Reaching People

Before trying to answer this question about squeezing energy consumption down to the bare minimum, we should consider an important human element in our forward thinking.

Consumer needs are clearly an important part of the discussion when we talk about content distribution methods. People with televisions that are not SmartTVs, or those who are only able to access DTT services, or those who do not have broadband (or sufficient broadband) services, should not be left behind by a change in content delivery method.

In the UK’s Broadcast 2040+ campaign, launched in June 2022 by Arqiva and supported by age-related action groups and rural community action groups, consideration is rightly given to the social complexity of simply switching off the broadcast networks or any other existing infrastructure. The research conducted for this campaign by Ipsos, a global market research firm specializing in public opinion, highlighted that:

  • 9 in 10 people in Great Britain want to see DTT supported
  • 43% of UK adults watch Freeview (the UK’s free to air service) every week
  • Age-related technology usage concerns make aerial-delivered TV easier for the elderly and most vulnerable
  • Availability of broadband in rural areas is a concern
  • The cost of buying broadband services are part of the current concern about the cost of living

Recognizing the impact on certain communities, Broadcast 2040+ is an important voice, representing the interests of the older, more vulnerable, and more remote parts of the UK’s population, and is mirrored in other countries facing similar situations. At the same time, to manage energy consumption and the CO2e impacts of content distribution, there are some hard choices to make about what to switch off and when.

Imagining The Future

Let’s imagine a content distribution scenario for the UK, with the following top-line data points:

  • Average viewing per person per day combines Broadcast, BVOD and SVOD for 255 minutes (4 hours and 5 minutes; see Article 1, Figure 2)
  • Device hours remain constant for a constant population size at 47 billion device hours per year
  • OTT viewing continues at 75% on TVs, with 25% on handheld/mobile devices
  • The bitrates delivered by OTT remain consistent with today’s average of c. 3.6 Mbps across all device types (source: Carnstone / Ofcom 2022, based on Netflix’s average in their ISP speed index from November/December 2021)
  • We maintain a typical daily viewing pattern consistent with today’s norms (Figure 5)
Figure 5: Typical daily viewing patterns of national broadcaster streaming services (source: industry analysis).

Figure 5: Typical daily viewing patterns of national broadcaster streaming services (source: industry analysis).

Using established models of streaming delivery, these parameters would lead to the following content delivery outcomes in terms of volume of content delivered and regular peak capacity required:

  • In the UK, streaming video from “Live TV”, “Recorded Playback”, “BVOD”, and “SVOD” would account for 77,000 Petabytes delivered per year
  • The routine peak streaming capacity required would be 52Tbps, delivering to 14 million concurrent devices. Note that this is for video streaming only and does not include simultaneous capacity required for radio/podcasts, gaming, internet browsing, videoconferencing, and other machine-based Internet of Things (IoT) use cases that also require delivery capacity.
  • If the average bitrate were to increase to 10Mbps, due to more UHD viewing, or advanced use cases like augmented reality and virtual reality media consumption, the above figures would approximately triple.

Based on the above outcomes – assuming no improvement in delivery system efficiency and acknowledging the Carnstone report’s warning to not speculate on future energy consumption using the attribution-based method, but recognizing that the 2021 energy consumption figures could mean less efficient content delivery for OTT versus DTT – then the energy consumption could be:

Figure 6: Estimated energy consumption, based on previously stated calculations and using the UK’s Average Total Wh consumed per Device hour.

Figure 6: Estimated energy consumption, based on previously stated calculations and using the UK’s Average Total Wh consumed per Device hour.

As a reminder, the UK’s combined 2021 DTT and OTT video content delivery consumed 4,300 GWh (Figure 4). This was 1.5% of the UK’s total 2021 electricity usage of 294 TWh (source: Statista).

The numerical results of this very brief analysis should be treated with some caution, given they are not attributing energy consumption and viewership in a precise way, but instead are extrapolating with data from the UK in 2021. But directionally, they provide an idea of what shifting to a 100% OTT model could mean. It is clear that changes must be made in the OTT infrastructure to become more efficient so that the M&E industry does not increase its overall energy consumption as streaming grows. But it also poses the big question about what to do with the DTT network, if/when DTT consumption decreases over time. The final part of this 3-part series explores the improvements being developed today, and some of the thinking taking place to ensure content distribution does its part to help the planet in the very-near future.

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