The ImageTrack interface of the WebCodecs API represents an individual image track.
ImageTrack
MDN Reference
The animated property of the ImageTrack interface returns true if the track is animated and therefore has multiple frames.
animated
true
The frameCount property of the ImageTrack interface returns the number of frames in the track.
frameCount
The repetitionCount property of the ImageTrack interface returns the number of repetitions of this track.
repetitionCount
The selected property of the ImageTrack interface returns true if the track is selected for decoding.
selected