InsufficientBufferRule

Description

The InsufficientBufferRule verifies each ABR choice to make sure the download is unlikely to cause a rebuffering event. The rule is best explained by looking at a concrete example. Assume the following values:

• currentThroughput = 5Mbit/s
• currentSafeThroughput = currentThroughput * throughputSafetyFactor = 5Mbit/s * 0.9 = 4.5 Mbit/s
• currentBufferLevel = 10 seconds
• segmentDuration = 4 seconds

To avoid a buffer underrun we need to finish the download of the next segment in 10 seconds. This means we need to download 4 seconds of content in 10 seconds. This leads us to the following expression that we need to solve:

possibleBitrate <= currentSafeThroughput * currentBufferLevel / segmentDuration

Plugging the examples values from above we get:

possibleBitrate <= 4.5 Mbit/s * 10s / 4s

So in this case we can select a maximum bitrate of 11.25 Mbit/s.

Configuration Options

Parameter	Description
throughputSafetyFactor	The safety factor that is applied to the derived throughput, see example in the Description.
segmentIgnoreCount	This rule is not taken into account until the first segmentIgnoreCount media segments have been appended to the buffer.

Example

player.updateSettings({
    streaming: {
        abr: {
            rules: {
                insufficientBufferRule: {
                    active: true,
                    parameters: {
                        throughputSafetyFactor: 0.9,
                        segmentIgnoreCount: 2
                    }
                }
            }
        }
    }
});