Subtitles in Nimble Streamer DVR – Softvelum: efficient tools to build your streaming networks

Nimble Streamer provides extended support for subtitles within the DVR (Digital Video Recorder) feature set. This allows storage, playback, and export of subtitle tracks from recorded live streams. The implementation is based on the WebVTT format and is fully compatible with HLS. It also has support for MPEG-DASH as an experimental feature.

Storing WebVTT Subtitles in DVR

When Nimble Streamer records live streams to DVR storage, it records WebVTT subtitle data associated with those streams. Subtitles are saved in sync with the corresponding audio and video tracks, ensuring proper alignment during playback and export. This enables consistent archiving of both the main media and associated text data for further processing or playback.

WebVTT for MPEG-DASH DVR

Nimble Streamer is able to provide subtitles for MPEG-DASH as experimental feature. Add the following parameters into nimble.conf file and re-start Nimble instance:

dash_webvtt_subtitles_enabled = true

This will enable WebVTT for DASH and will provide respective DVR subtitles.

Multiple Subtitle Tracks for HLS and MPEG-DASH from DVR

DVR playback supports multiple WebVTT subtitle tracks when delivering content through HLS or MPEG-DASH. This means that a recorded stream containing several subtitle tracks (for example, different languages) will have all of them available to the player. The subtitle selection during playback is performed by the player, allowing end users to choose a preferred track dynamically, the same way as in live streaming scenarios.

Exporting Recorded WebVTT Subtitles

Nimble Streamer provides an API for exporting recorded WebVTT subtitles from DVR. This allows external systems to retrieve subtitle files for additional processing, correction, or storage outside Nimble The API supports retrieving complete subtitle files associated with specific streams and time ranges.
See the Nimble API documentation for details on the request structure and available parameters.

When exporting subtitles, users can specify which subtitle track to extract from DVR.
This is useful in cases where multiple subtitle languages or variants exist for a single stream. The export process can be configured to target a specific track by its ID or language code, reducing post-processing effort.