Analyze Tracks Workflow Operation

ID: analyze-tracks

Description

The analyze-tracks operation analyzes specified tracks in the mediapackage and sets workflow instance variables based on the tracks audio and video properties. These variables can then be used to control if workflow operations should be executed.

Note that this operation should be preceded by the inspect workflow operation handler.

For all tracks matching the flavor specified by the mandatory configuration key source-flavor, the following workflow instance variables may be set:

Name	Example	Description
flavor_media	presenter_source_media=true	Track with specific favor exists
flavor_audio	presenter_source_audio=true	Track contains at least one audio stream
flavor_video	presenter_source_video=true	Track contains at least one video stream
flavor_subtitle	presenter_source_subtitle=true	Track contains at least one subtitle stream
flavor_resolution_x	presenter_source_resolution_x=1280	Horizontal resolution of the video stream
flavor_resolution_y	presenter_source_resolution_y=720	Vertical resolution of the video stream
flavor_aspect	presenter_source_aspect=4/3	Exact aspect ratio of the video stream
flavor_aspect_snap	presenter_source_aspect_snap=4/3	Nearest specified aspect ratio of the video
flavor_framerate	presenter_source_framerate=30.0	Framerate of the video stream

Parameter Table

Configuration Key	Example	Description
source-flavor*	presentation/work	The "flavor" of the track to use as a source input
aspect-ratio	4/3,16/9	Snap to these aspect ratios if specified
fail-no-tracks	false	Fail if flavor matches no tracks (Default: false)

* mandatory configuration key

Note that if there are multiple video streams with one flavor, only the information from the last video stream are taken.

Snap to Aspect Ratio

Snap-to-aspect can be used to deal with slightly off resolutions. Given an SAR of 1, for example, a video with the resolution of 640x481 pixels has almost an aspect ration of 4/3, but is 1 pixel too wide. For special encoding options or cover generation, it would still be reasonable to use the 4/3 settings. If 4/3 is listed in the aspect-ratio option, …_aspect_snap would be set to 4/3.

Operation Example

<operation
    id="analyze-tracks"
    description="Analyze tracks in media package and set control variables">
  <configurations>
    <configuration key="source-flavor">*/source</configuration>
    <configuration key="aspect-ratio">4/3,16/9</configuration>
  </configurations>
</operation>

If a video track with a resolution of 1280x720 and an included audio stream is passed to this operation as presentiation/source, the resulting variables would be:

presentation_source_aspect=16/9
presentation_source_aspect_snap=16/9
presentation_source_audio=true
presentation_source_media=true
presentation_source_resolution_x=1280
presentation_source_resolution_y=720
presentation_source_video=true
presentation_source_framerate=30.0