SwitchHistoryRule

Description

Frequent quality switches result in a negative QoE for the end-user. The main objective of the SwitchHistoryRule is to to detect and avoid any extreme bitrate oscillations allowed by the ABR algorithms. For that reason, the SwitchHistoryRule monitors quality down-switches. It derives a ratio of down-switches divided by the number of times the quality stayed the same or even improved. If this ratio exceeds the switchPercentageThreshold the quality is reduced.

if (drops + noDrops >= settings.get().streaming.abr.rules.switchHistoryRule.parameters.sampleSize
    && (drops / noDrops > settings.get().streaming.abr.rules.switchHistoryRule.parameters.switchPercentageThreshold)) {
    switchRequest.representation = (i > 0 && switchRequests[currentPossibleRepresentation.id].drops > 0) ? representations[i - 1] : currentPossibleRepresentation;
}

Configuration Options

Parameter	Description
minimumSampleSize	Sum of ABR quality checks required before the rule kicks in.
switchPercentageThreshold	Ratio of quality drops compared to no quality drops must exceed this threshold before a potential quality down-switch by the SwitchHistoryRule is enforced.

Example

player.updateSettings({
    streaming: {
        abr: {
            rules: {
                switchHistoryRule: {
                    active: true,
                    parameters: {
                        minimumSampleSize: 8,
                        switchPercentageThreshold: 0.075
                    }
                }
            }
        }
    }
});