音频视频的播放的进度调整(以.net为例)

Background：对于音视频在线播放，一些小应用是靠nginx处理访问视频、音频文件的请求，对外应用的一般会托管至各种云上使用相关的服务。前者存在巨大的安全隐患，后者会有一定的成本。有的时候还是需要自己造个轮子。

step 1：先实现文件下载

[HttpGet]
public IActionResult Get()
{    
    var filePath = @"E:	est.wav";
    var name = @"tes1t.wav";
    FileStream fs = new FileStream(filePath, FileMode.Open);
    return  File(fs, "application/octet-stream", name);
}

前面的audio标签是可以播放和正常下载的，但是并不能实现进度控件的调整

step2：请求的区别

Nginx的处理是可以实现播放进度调整的。在前端请求相同的情况下，两者用nginx代理和刚才的下载的主要区别如下：

可以看出Content-Range对应的正是请求头中的Range

关于这几个头部信息可参考这篇文章：https://blog.csdn.net/thewindkee/article/details/80189434

这3个标签同时也是文件实现断点续传的关键。

step3：断点续传

这样进度的调整就转化为了断点续传功能。

.net可参考：https://www.cnblogs.com/Leo_wl/p/8467796.html

 public FileStreamResult Index(string auth,string filename)
        {
            if (auth != null && auth.Length >7)
            {
                 // 处理权限问题
            }
            else
            {
                return null;
            }
            
            int size, end, length = 0;
            int start;

            MemoryStream Mstream;
            using (FileStream reader = new FileStream(filename, FileMode.Open, FileAccess.Read, FileShare.Read))
            {
                byte[] bytes = new byte[reader.Length];
                //var strd = new StreamReader(reader);

                size = bytes.Length;
                start = 0;
                end = size - 1;
                length = size;
                Response.Headers["Accept-Ranges"] = "0-" + size;
                if (!String.IsNullOrEmpty(Request.Headers["Range"]))
                {
                    int anotherStart = start;
                    int anotherEnd = end;
                    var headerRange = Request.Headers["Range"];
                    string[] arr_split = headerRange.FirstOrDefault().Split(new char[] { Convert.ToChar("=") });
                    Debug.WriteLine(arr_split);
                    string range = arr_split[1];
                    if (range.IndexOf(",") > -1)
                    {
                        Response.Headers["Content-Range"] = "bytes " + start + "-" + end + "/" + size;

                        Response.StatusCode = 416;

                    }
                    if (range.StartsWith("-"))
                    {
                        // The n-number of the last bytes is requested
                        anotherStart = size - Convert.ToInt32(range.Substring(1));
                    }
                    else
                    {
                        arr_split = range.Split(new char[] { Convert.ToChar("-") });
                        anotherStart = Convert.ToInt32(arr_split[0]);
                        int temp = 0;
                        anotherEnd = (arr_split.Length > 1 && Int32.TryParse(arr_split[1].ToString(), out temp)) ? Convert.ToInt32(arr_split[1]) : size;
                    }
                    anotherEnd = (anotherEnd > end) ? end : anotherEnd;
                    if (anotherStart > anotherEnd || anotherStart > size - 1 || anotherEnd >= size)
                    {
                        Response.Headers["Content-Range"] = "bytes " + start + "-" + end + "/" + size;
                        Response.StatusCode = 416;

                    }
                    start = anotherStart;
                    end = anotherEnd;
                    length = end - start + 1; // Calculate new content length
                    reader.Read(bytes, start, length);
                    Response.StatusCode = 206;
                }
                else
                {
                    reader.Read(bytes, 0, bytes.Length);
                }
                Mstream = new MemoryStream(bytes);
            }
            Response.Headers["Content-Range"] = "bytes " + start + "-" + end + "/" + size;
            Response.Headers["Content-Length"] = length.ToString();
            Response.Headers.Add("Content-Disposition", "attachment; filename=download.wav");
            return new FileStreamResult(Mstream, "applicaton/octet-stream");
        }