by Thomas Koller and Han Sloetjes

ANNEX and ELAN are two closely related applications designed for handling of digital media files and associated annotation files. While ELAN as a desktop application is used for the creation of rich annotations on audio and video recordings, ANNEX represents a web-based viewer which allows to study annotated resources once they have been properly stored on the archive server.

This short article aims at highlighting on the one hand what features they have in common and on the other hand what features are unique to each tool.

ELAN is a local tool (desktop application) for the creation of annotations to audio and or video recordings. It is a combination of a media player with viewer and editor components for annotations. The annotation documents are stored in the XML-based ELAN Annotation Format (EAF). ELAN is written in the Java programming language and is available for Windows, Mac OS X and Linux. On Windows and Mac the media playback is delegated to an available high performance native media framework: DirectX/DirectShow on Windows and QuickTime on Mac. On Linux JMF is used. The list of supported file types depends on the available media player frameworks.

ELAN main window

Although there is limited support for streaming media via the RTSP protocol, most commonly the media files are accessed directly on a local hard drive or the local network. This guarantees high accuracy in media playback, especially in (repeated) playback of fragments of the media, which is usually a basic step in the process of segmenting the media. The annotation boundaries can be determined with millisecond precision. ELAN supports simultaneous, synchronized playback of up to 4 video files. The annotation documents are stored locally as well. The variant of the TROVA search engine that is distributed with ELAN can query the contents of physical directory structures. To that end it creates temporary in-memory indexes for the content of selected folders and files. The search is limited to EAF files. The ELAN window offers several customizable views on the annotation data, all synchronized with the media player. All viewers are editors at the same time. Many operations are provided for manipulating tiers and annotations.

ANNEX is written as an ELAN compliant browser-based tool (web application) that supports media playback via HTTP pseudostreaming and the Flash Player browser plugin. For freely accessible language resources ANNEX can also be embedded in any web page by pasting a simple HTML snippet into the page (comparable to the way Youtube supports embedding of videos into web pages). Alongside the media player it contains several customizable viewer components for annotations. By default both the media files and the annotation files are streamed from the MPI online archive; there is no need for downloading files in order to be able to view their contents. ANNEX is seamlessly integrated with the archive access management tools and interacts with available web services, for example the ones exposed by the lexicon tool LEXUS. Other tools in turn can make parameterized calls to ANNEX.

ANNEX works with the online version of TROVA, which creates an index for a whole LAMUS archive using the Postgres database system. This version of TROVA supports not only EAF but also Shoebox, CHAT and generic XML, HTML and text files.

Comparison Matrix
Number of synchronized videos 1 4
Media file types MPG for video files, WAV for audio files Depending on the media framework of the particular platform
Waveform for audio .wav only .wav only
Media playback precision Depends on keyframe rate milliseconds
Streaming media support Pseudostreaming for audio and video files Limited, via rtsp
Annotation formats EAF, Toolbox/Shoebox, Chat. Will be converted to a single XML format for transfer. EAF, import of Toolbox, Chat, Praat, Transcriber, CSV
Annotation editing No Yes
Number of tiers Unlimited Unlimited
Font usage Any font available on the system Any font available on the system supported by Java
Search options TROVA search engine, search in entire (accessible part of) archive Single file search and multiple file search (TROVA) in local corpus
Technology Flash, XML, Quicktime (temporarily for resources with master audio file) Java, XML
Tool interaction, API Support for parameterized calls to ANNEX Extension mechanism for particular parts of the application