July 24, 2025

HbbTV Reference Applications: Enhancing interoperability and conformance across the ecosystem

In a recent HbbTV webinar, leading voices from across the connected TV ecosystem gathered to explore the role of reference applications in supporting conformance, interoperability, and robust application development. Hosted during the European summer, the session drew substantial interest despite its technical depth, a clear sign of the growing importance of reference applications in the development and testing of HbbTV services.

The webinar featured insights from Bob Campbell (Global Head of Conformance and Interoperability at Resillion), Mark Reilly and Alex Russell (Senior Architect and Controller of Technical Partnerships at Everyone TV), and Mirko Nedeljkovic (CEO of Suitest). Each speaker addressed different but complementary aspects of HbbTV reference apps, ranging from foundational concepts and real-world implementations to remote testing practices and collaborative tools.

This article offers an overview of the themes discussed and highlights key takeaways from each speaker’s presentation.

Why reference applications matter

The HbbTV ecosystem depends on a combination of technical standards, conformance tools, and collaborative testing practices to ensure that applications work reliably across a diverse range of devices and use cases. Reference applications play a pivotal role by demonstrating how HbbTV features should work in practice. They complement formal conformance tests by focusing on real-world interoperability, user experience validation, and system-level integration.

Bob Campbell opened the webinar by framing the discussion within this wider context. He explained that while the HbbTV conformance test suite provides essential unit-level validation (with over 3,000 tests covering APIs and functional requirements), it is not designed to test how features interact in the context of full applications or services. This is where reference applications step in, to provide executable, observable, and reusable implementations that illustrate how specifications behave in actual use.

Bob Campbell (Resillion): Building and using reference applications effectively

Bob Campbell’s presentation laid out the distinction between conformance (unit testing of specification compliance) and interoperability (system-level functionality across devices and services). His key message: reference apps help fill the interoperability gap by allowing vendors, developers, and test labs to validate more complex scenarios involving content playback, UI interactions, and platform-specific behaviours.

Characteristics of good reference applications

According to Campbell, a good reference application must:

• Be easy to understand, both in function and expected outcomes.
• Be globally accessible and free of restrictions like geo-blocking.
• Remain stable and version-controlled, avoiding frequent untracked changes.
• Be well-documented, enabling test teams to understand its user journey and expected states.
• Provide insight into what “good” looks like, particularly important in remote or automated testing environments.

He also emphasized the value of transparency: HbbTVs DRM reference app, for example, is fully open source and hosted on GitHub, enabling manufacturers and developers to inspect the implementation directly. The application includes scenarios for multiple DRM schemes, live streaming, subtitles, and adaptive bitrate streaming, with new features introduced in a staged manner across test, staging, and production environments.

Best practices and plugfests

Campbell outlined how HbbTV’s reference app is tested across a “zoo” of 20–25 devices and continuously updated. He also shared Resillion’s experiences organizing virtual Plugfests, including a recent session in Shenzhen in collaboration with Suitest. These events enable geographically distributed developers and manufacturers, especially in Asia, to validate apps and devices without the need for travel. Reference apps were a critical component in enabling remote testing and ensuring consistent expectations across participants.

Mark Reilly (Everyone TV): Implementing a complex reference use case

Mark Reilly provided a developer’s perspective, showcasing a highly specific reference application built to support Everyone TV’s Freely service. This reference app is centred on an OpApp implementation using a secondary video window, a sophisticated setup that allows IP-based channels to be shown alongside HbbTV UI layers.

The OpApp secondary video window

Everyone TV’s OpApp enables access to over 150 channels across DTT and IP, through a dedicated video window while maintaining a user interface layer for guide information and interactivity. The secondary video window operates as a separate application and uses dash.js for playback, along with Media Source Extensions (MSE) and Encrypted Media Extensions (EME) for handling PlayReady SL2000 and SL3000 DRM.

Reilly explained that this proof-of-concept app was created in parallel with specification development to enable early prototyping and debugging. While not a formal conformance app, it has served as a valuable developer aid and reference point for manufacturers integrating support for the Freely service.

Architecture and communication

The setup involves multiple composited elements:

• The OpApp provides the main user interface.
• A secondary video window handles playback.
• A graphics window supports subtitles.

These layers are composited on the terminal using a defined z-order. Communication between the app and the terminal occurs via JSON-RPC over WebSockets, enabling status updates, playback control, and channel selection. Metrics such as buffer state, bitrate, CPU usage, and proximity to live edge are continuously tracked and visualized to assess performance.

Reilly shared examples of issues identified using this framework, such as ad stream playback failures due to CORS misconfiguration and bandwidth contention scenarios where devices adjust representation quality dynamically.

Alex Russell (Everyone TV): From reference to conformance with TaCO

Expanding on Reilly’s presentation, Alex Russell introduced Everyone TV’s TaCO app (Test and Conformance OpApp). Whereas the secondary video window app focused on playback, TaCO targets key API coverage across the OpApp specification (HbbTV 1.2.1).

TaCO: Two apps in one

TaCO is both:

• A real OpApp implementation used to initiate API calls and receive responses.
• A test app capable of executing automated or manual test packages.

TaCO is designed to separate usability and presentation from API validation. It uses on-screen logging and user prompts to help verify behaviour, with test packs updated independently of the main application. While some tests require manual input (e.g., checking time accuracy), the goal is to maximize automation.

Role in conformance

Unlike the Freely video window app, TaCO is explicitly part of Everyone TV’s conformance process. Device manufacturers seeking to use the Freely trademark must run TaCO, verify results, and collaborate with Everyone TV on resolving failures. The application is effective at uncovering unimplemented APIs, malformed responses, and stubbed-out functionality, critical issues for ensuring spec compliance and device readiness.

Russell also announced the formation of a new HbbTV Study Mission Group called Test and Conformance Apps (TaCA) which will investigate how reference applications can be more systematically incorporated into HbbTV tools and practices. Topics include licensing, versioning, and the validation of community-contributed apps.

Mirko Nedeljkovic (Suitest): Remote testing at scale

The final presentation came from Mirko Nedeljkovic, CEO of Suitest, who discussed a groundbreaking interoperability event held in Shenzhen. Conducted in partnership with Resillion, the event marked the first-ever Plugfest in the APAC region.

Virtual plugfest setup

Suitest specializes in OTT test automation for living room devices, with deep support for HbbTV. During the event, eight Android and Fire TV OS devices from TCL, Skyworth, and TCL Mocha were connected to the Suitest platform, enabling developers in Europe to test HbbTV and Android apps remotely.

Key features of the remote setup included:

• Virtual remote controls
• Real-time video streaming from test devices (via phone cameras or HDMI capture)
• On-screen console logs and performance data
• Dedicated local streaming server to reduce latency (100–200ms to the UK)

Participants were able to test pre-production models, compare behaviour with retail devices, and interact directly with manufacturers via video link.

Lessons learned

Nedeljkovic highlighted the benefits and challenges of remote testing:

• Positive feedback on real-time interaction and early access to devices
• Desire for broader manufacturer participation and more detailed device specifications
• Importance of planning, especially for ensuring video capture compatibility and network access

He noted that despite the technical complexity, the remote Plugfest matched the effectiveness of in-person events while aligning with broader industry goals around sustainability and reduced travel.

Panel and Q&A: Performance, certification, and standards evolution

In the concluding panel session, the speakers addressed several audience questions, covering:

• The role of reference apps in setting performance expectations: While difficult to define objectively, performance can be measured through metrics like playback speed and transition latency, as in targeted advertising specs.
• Integration with test tools like Resillion’s Ligada: Ligada can already automate testing of HbbTV reference apps.
• API usage and tag strategy: Questions about the use of multiple video tags and HTML objects were deferred to GitHub issue tracking, emphasizing the open-source and collaborative nature of the reference apps.
• Focus handling and UI robustness: Future iterations of test apps may include more scenarios involving key event management to ensure smooth user control.

Conclusion

This webinar offered a comprehensive look into how reference applications are enabling more robust and interoperable HbbTV deployments across the globe. From open-source examples like the DRM reference app to complex implementations such as Everyone TV’s OpApp, the ecosystem is embracing reference apps as critical tools, not only for developers and testers but also for manufacturers and certifiers.

As HbbTV services continue to grow in scope and complexity, the importance of collaborative testing, remote validation, and community-driven tool development will only increase. The initiatives discussed during the session, especially the launch of the TaCA study mission group, signal a strong commitment to evolving the HbbTV ecosystem with openness, scalability, and quality at its core.

Matthew Huntington
Manager of the HbbTV Developer Programme