BBA0的getMaxIndex()函数怎么写
时间: 2024-02-15 17:03:09 浏览: 24
BBA算法是一种基于缓冲区占用率和历史码率的自适应码率算法。其核心思想是通过最小化缓冲区占用率和码率的方差来确定最优码率。下面是BBA0算法的getMaxIndex函数的示例代码:
```
function getMaxIndex(rulesContext) {
const switchRequestHistory = rulesContext.getSwitchHistory();
const dashMetrics = rulesContext.getDashMetrics();
const mediaType = rulesContext.getMediaInfo().type;
const abrController = rulesContext.getAbrController();
const throughputHistory = abrController.getThroughputHistory();
const latencyHistory = abrController.getLatencyHistory();
const bitrateList = abrController.getBitrateList(mediaType);
const currentBufferLevel = dashMetrics.getCurrentBufferLevel(mediaType);
// Calculate average throughput and latency.
const avgThroughput = throughputHistory.getAverageThroughput(mediaType);
const avgLatency = latencyHistory.getAverageLatency(mediaType);
// Calculate the harmonic mean of throughput and latency.
const harmonicMean = avgThroughput * avgLatency;
// Calculate the buffer size in seconds.
const bufferSize = currentBufferLevel / (harmonicMean / 8);
// Calculate the buffer occupancy in seconds.
const bufferOccupancy = bufferSize - currentBufferLevel;
// Calculate the current bitrate and the average bitrate.
const currentBitrate = abrController.getQualityFor(mediaType, currentBufferLevel);
const avgBitrate = dashMetrics.getCurrentRepresentationSwitch(mediaType).quality > 0 ?
dashMetrics.getCurrentRepresentationSwitch(mediaType).quality :
abrController.getAverageThroughput(mediaType, true) / 1000;
// Calculate the variance of bitrate and buffer occupancy.
const bitrateVariance = dashMetrics.getVariance(mediaType, true, avgBitrate);
const bufferVariance = dashMetrics.getVariance(mediaType, false, bufferOccupancy);
// Calculate the score.
const score = (bitrateVariance / avgBitrate) + (bufferVariance / bufferOccupancy);
// Find the optimal bitrate.
let optimalBitrate = currentBitrate;
let optimalScore = score;
for (let i = 0; i < bitrateList.length; i++) {
if (bitrateList[i].bandwidth / 1000 <= avgThroughput) {
const tempBitrate = bitrateList[i].quality;
const tempScore = (bitrateList[i].bandwidth / 1000 / avgBitrate - 1) * Math.sqrt(bitrateVariance / bufferVariance) + score;
if (tempScore < optimalScore) {
optimalBitrate = tempBitrate;
optimalScore = tempScore;
}
}
}
// Create a switch request.
const switchRequest = SwitchRequest(context).create(optimalBitrate, { BBA0: optimalScore });
return switchRequest;
}
```
该函数首先获取播放器的状态,包括缓冲区状态、码率序列和网络状态等。然后,根据BBA算法的思想,计算出当前最优的码率,并返回码率切换请求。