Question

我正在尝试获取WebClient下载文件的当前下载速度，但是当我使用我非常确定应该解决的公式时：

Stopwatch.Stop();
double msElapsed = Stopwatch.Elapsed.TotalMilliseconds;
int bytesDownloaded = (int)e.BytesReceived - lastBytesDownloaded;
double downloadSpeed = (double)bytesDownloaded / (msElapsed / 1000);
lastBytesDownloaded = (int)e.BytesReceived;
Stopwatch.Restart();

当秒表是我在启动文件下载时启动的秒表时，lastBytesDownloaded是一个类变量，这都在downloadProgressChanged事件中，但是下载速度与实际情况相差很大。

例如，如果我以500kb / s的速度下载文件，它将迅速从（例如）10kb / s快速跳转到50mb / s。

通过对其进行一些编辑，我可以获得准确的平均下载时间：

double sElapsed = Stopwatch.Elapsed.TotalSeconds;
int bytesDownloaded = (int)e.BytesReceived;
double downloadSpeed = bytesDownloaded / sElapsed;

但这不是我想要的。如何为当前下载速度获得更稳定的读数？

Answer 1

您需要在更长的时间内smooth数据。例如，不要仅根据最后一次测量报告当前下载速度;使用a（可能是weighted）moving average代替。

死的简单例子：

var measurements = 0, maxDataPoints = 5;
var dataPoints = new double[maxDataPoints];

然后：

Stopwatch.Stop();
double msElapsed = Stopwatch.Elapsed.TotalMilliseconds;
int bytesDownloaded = (int)e.BytesReceived - lastBytesDownloaded;
lastBytesDownloaded = (int)e.BytesReceived;
double dataPoint = (double)bytesDownloaded / (msElapsed / 1000);
dataPoints[measurements++ % maxDataPoints] = dataPoint;

double downloadSpeed = dataPoints.Average();
Stopwatch.Restart();

WebClient DownloadDataAsync当前下载速度

1 个答案: