Select Tracks Workflow Operation

ID: select-tracks

Description

The select-tracks operation can be used in case not all source tracks should be processed. For example, given a recording with a presenter and a presentation track, the final recording to be published should only include the video stream of the presenter track and the audio stream of the presentation track.

The workflow operation will use workflow properties set by the Opencast video editor to determine which tracks should be selected for further processing and add them to the media package based on target-flavor and target-tags.

IMPORTANT: The input tracks need to be inspected using the workflow operation inspect before running this operation.

Parameter Table

Configuration Key	Example	Description
source-flavor*	*/source	The flavor of the track(s) to use as a source input
target-flavor*	*/work	The flavor of the target track(s)
target-tags	download	The tags applied to all target tracks
audio-muxing	force	Move single-audio media packages to a specific track (see below)
force-target	presenter	Target track for the force setting for audio-muxing

* mandatory configuration key

Workflow Properties

The names of the workflow properties that control which streams are included in the output tracks are

"hide_" + source-flavor.type + "_audio"
"hide_" + source-flavor.type + "_video"

Example:

For the source flavor presenter/work, use the boolean workflow properties hide_presenter_audio and hide_presenter_video to control which streams should be included in the output tracks.

Those properties are set by the Opencast video editor and can also be set using a custom workflow configuration panel.

Audio Muxing

The optional audio-muxing parameter has three possible values: none (same as omitting the option), force and duplicate.

none

If none is specified or the option is omitted, the audio stream is taken from the specified source-flavor track and is edited according to the selections in video editor’s “Tracks” panel. The resulting tracks are stored in the corresponding target-flavor and target-tags are applied.

Note: If your editing results in a single video and single audio (track/stream) they will be muxed together even if this option is set to none.

force

The parameter value force only applies to media packages that have exactly one non-hidden audio stream. For media packages without an audio stream or with more than one audio stream, the behavior is the same as if the parameter were omitted. The same applies to media packages for which there is only one audio stream, and it already belongs to the track with flavor type given by force-target (or presenter if that parameter is omitted).

If, however, there is only one non-hidden audio stream and it does not belong to the track given by force-target, then the operation will “move” the audio stream to this target track. Specifically, it will mux the video stream of force-target with the audio stream it found. Then, it removes the audio stream from the original track.

For example, consider a media package with two tracks, presenter and presentation. Both of these tracks have audio components, however the presenter audio stream is hidden. This WOH will mux presentations's audio stream with presenter's video, and remove the audio track from presentation's video.

duplicate

The parameter value duplicate only applies to media packages that have exactly one non-hidden audio stream and no hidden video streams. For these media packages, the WOH will mux the audio stream it found to all video streams in the media package. For media packages without an audio stream or with more than one audio stream, the behavior is the same as if the parameter were omitted.

Encoding Profiles

This workflow operation handler depends on the presence of the following encoding profiles:

Name	Description
video-only.copy	Removes all audio streams from a media track
audio-only.copy	Removes all video streams from a media track
mux-av.copy	Mux a video stream and an audio stream into a media track

Note that those encoding profiles are included in the default configuration of Opencast.

Operation Example

<operation
    id="select-tracks"
    description="Select tracks for further processing">
  <configurations>
    <configuration key="source-flavor">*/source</configuration>
    <configuration key="target-flavor">*/work</configuration>
    <configuration key="audio-muxing">force</configuration>
  </configurations>
</operation>