isAutoSynced property
Indicates whether YouTube synchronized the caption track to the audio track in the video.
The value will be true if a sync was explicitly requested when the caption track was uploaded. For example, when calling the captions.insert or captions.update methods, you can set the sync parameter to true to instruct YouTube to sync the uploaded track to the video. If the value is false, YouTube uses the time codes in the uploaded caption track to determine when to display captions.
Implementation
core.bool? isAutoSynced;