Multiperiod Streams

A DASH MPD can contain multiple Period elements. Each period defines its own set of Adaptation Sets and Representations and can differ from the previous period, for instance in codecs, available tracks or content protection. Multiperiod streams are commonly used for ad insertion and for concatenating different pieces of content into a single presentation.

How dash.js handles periods

dash.js supports multiperiod streams for both VoD and live content out of the box, no additional configuration is required:

const player = dashjs.MediaPlayer().create();
player.initialize(videoElement, mpdUrl, true);

Internally, dash.js creates one Stream object per period. When playback approaches a period boundary, the player prepares the next period ahead of time and performs a seamless transition. The current track and quality settings are re-applied after each transition: dash.js tries to continue with the same language, role and quality settings that were active in the previous period.

Period switch events

To get notified about period transitions, subscribe to the corresponding player events:

player.on(dashjs.MediaPlayer.events.PERIOD_SWITCH_STARTED, (e) => {
    console.log('Switching from period', e.fromStreamInfo ? e.fromStreamInfo.index : null,
        'to period', e.toStreamInfo.index);
});

player.on(dashjs.MediaPlayer.events.PERIOD_SWITCH_COMPLETED, (e) => {
    console.log('Now playing period', e.toStreamInfo.index);
});

• PERIOD_SWITCH_STARTED is triggered when the player starts the transition to a new period. The payload contains fromStreamInfo (null at playback start) and toStreamInfo.
• PERIOD_SWITCH_COMPLETED is triggered once the new period is active. The payload contains toStreamInfo.

The streamInfo objects expose useful information such as id, index, start and duration of the corresponding period.

Sample

• Multiperiod VoD - VoD stream with two periods.
• Multiperiod live - Live stream with multiple periods.