gingaf: Headless and Multiplatform Execution of ITU-SBTVD NCL Applications¶

University of Reading

ACM MM 2026

DOI Pre-print Slides Code Repo Paper Repo

Abstract¶

The Nested Context Language (NCL) is a core component of the ITU-T and SBTVD television standards. It is legally mandated and installed on 100% of certified Digital TV sets and set-top boxes across Brazil and several Latin American countries. This massive deployment impacts over 60 million people. However, the ecosystem of NCL development tools is limited. In this context, we present gingaf, an open-source implementation of an NCL player built in Flutter. It supports a headless execution engine that schedules NCL events in-memory without requiring any UI and provides a foundation for NCL developer tooling. We also proposed a UI component that achieves multiplatform visual rendering of NCL documents on Windows, mobile, and Web from a single codebase.

Architecture¶

gingaf is built around two main components (Figure below): the NCL Logic as a self-contained execution engine that manages the NCL event state machine with no knowledge of any display context; and NCL UI as a Flutter widget that drives the engine and maps its output to native platform widgets.

Example: Multiplatform Execution¶

The following NCL code (video.ncl) demonstrates a simple video presentation with two synchronized background images that appear sequentially. This illustrates the capabilities of NCL for multiplatform environments.

<ncl>
  <body>
    <port id="init" component="video"/>
    <media id="video" src="https://flutter.github.io/assets-for-api-docs/assets/videos/butterfly.mp4">
      <area id="a1" begin="2s" end="4s"/>
    </media>
    <media id="green_bg">
      <property name="background" value="green"/>
      <property name="bounds" value="0%,80%,20%,20%"/>
    </media>
    <media id="red_bg">
      <property name="background" value="red"/>
      <property name="bounds" value="80%,80%,20%,20%"/>
      <property name="explicitDur" value="2s"/>
    </media>
    <link id="l1">
      <bind role="onBegin" component="video" interface="a1"/>
      <bind role="start" component="green_bg"/>
    </link>
    <link id="l2">
      <bind role="onEnd" component="video" interface="a1"/>
      <bind role="stop" component="green_bg"/>
      <bind role="start" component="red_bg"/>
    </link>
  </body>
</ncl>

Multi-platform Demos¶

Windows	Android
Chrome	CLI (headless execution)

Execution Instructions¶

To run the gingaf (either the presentation layer with GUI or the headless execution engine for testing), execute the following commands:

git clone -b v0.1.0 https://github.com/ginga-org-br/gingaf
cd gingaf/ncldoc
make deps
dart lib/main.dart ../ginga/examples/video.ncl
cd ../ginga
make deps # See SETUP.md for environment configuration
flutter run -d <chrome,windows,emulator-XXXX> --dart-define="APP=examples/video.ncl"

Citation¶

@inproceedings{gingaf2026,
    author    = {Guedes, Alan},
    title     = {gingaf: Headless and Multiplatform Execution of ITU-SBTVD NCL Applications},
    booktitle = {Proceedings of the 34th ACM International Conference on Multimedia},
    location  = {Rio de Janeiro, Brazil},
    year      = {2026},
    doi       = {10.1145/3767308.3834744},
    url       = {https://dl.acm.org/doi/10.1145/3767308.3834744},
    series    = {MM '26}
}