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_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