startPosition

Where to start. Null means the beginning, or the container's own start time. With a clip it counts from the clip's start, as every position of a clipped item does, and null means the clip's start.

Honoured in two halves: the source is moved to the keyframe at or before this position BEFORE the first frame is decoded, so nothing from the beginning of the media is ever shown or heard, and the exact landing then rides an ordinary precise seek. Needs a seekable source; a position that cannot be honoured (unseekable media, or past the end) starts at the beginning and warns StartPositionIgnored, typed.