A seek is initiated by BigscreenPlayer#setCurrentTime(). It can take a number or a number and a timeline. Each timeline is defined in the Timeline enum.

BigscreenPlayer will signal a seek is in progress through the isSeeking property on the WAITING state change.

Setting a start point

A call to setCurrentTime() does nothing until the stream is loaded with BigscreenPlayer#init(). You should provide an initialPlaybackTime in the initialisation object instead, like:

bigscreenPlayer.init(playbackElement, {
  ...init,
  initialPlaybackTime: 30, // a presentation time in seconds
})

The initialPlaybackTime can also reference other timelines, just like setCurrentTime()

bigscreenPlayer.init(playbackElement, {
  ...init,
  initialPlaybackTime: {
    seconds: 30,
    timeline: Timeline.MEDIA_SAMPLE_TIME,
  },
})

Timelines

The Timeline constant enumerates different reference points you can seek through a stream by. This section explains each timeline.

Presentation time

The time output by the MediaElement. The zero point is determined by the stream and transfer format (aka streaming protocol). For example, for HLS 0 always refers to the start of the first segment in the stream on first load.

Presentation time is output by BigscreenPlayer#getCurrentTime() and BigscreenPlayer#getSeekableRange(). The value provided to setCurrentTime() and initialPlaybackTime is treated as presentation time by default.

Media sample time

The timestamps encoded in the media sample(s).

For DASH the conversion between media sample time and presentation time relies on the presentationTimeOffset and timescale defined in the MPD. BigscreenPlayer assumes the presentation time offset (in seconds) works out as the same value for all representations in the MPD.

For HLS the conversion between media sample time and presentation time relies on the programDateTime defined in the playlist. BigscreenPlayer assumes the programDateTime is associated with the first segment in the playlist.

Availability time

The UTC time denoting the availability of the media. Only applies to dynamic streams.

For DASH the conversion between availability time and presentation time relies on the availabilityStartTime. BigscreenPlayer assumes the stream doesn't define any availabilityOffset.

For HLS the conversion is erroneous, and relies on programDateTime. See decision record 007-estimate-hls-ast.