我之前使用过
http://www.strathweb.com/2013/01/asynchronously-streaming-video-with-asp-net-web-api/这种技术,并且非常适合异步视频流.
但对于ASP.NET Core,这种方式并没有按预期工作.
通过视频流类是:
public class VideoStream { private readonly string _filename; public VideoStream(string filename) { _filename = filename; } public async Task WriteToStream(Stream outputStream,HttpContent content,TransportContext context) { try { var buffer = new byte[65536]; using (var video = File.Open(_filename,FileMode.Open,FileAccess.Read)) { var length = (int)video.Length; var bytesRead = 1; while (length > 0 && bytesRead > 0) { bytesRead = video.Read(buffer,Math.Min(length,buffer.Length)); await outputStream.WriteAsync(buffer,bytesRead); length -= bytesRead; } } } catch (Exception) { return; } finally { outputStream.Flush(); outputStream.Dispose(); } } }
我对视频流请求有以下操作:
[HttpGet] [Route("[action]")] public IActionResult GetVideo(int id) { var fileName = GetVideoFileName(id); var video = new VideoStream(fileName); var response = new HttpResponseMessage { Content = new PushStreamContent(video.WriteToStream,new MediaTypeHeaderValue("video/mp4")) }; var objectResult = new ObjectResult(response); objectResult.ContentTypes.Add(new Microsoft.Net.Http.Headers.MediaTypeHeaderValue("video/mp4")); return objectResult; }
由于默认情况下Asp.Net Core没有内置的Media Formatter for video / mp4我创建了以下自定义媒体格式化程序
public class VideoOutputFormatter : IOutputFormatter { public bool CanWriteResult(OutputFormatterCanWriteContext context) { if (context == null) throw new ArgumentNullException(nameof(context)); return true; } public async Task WriteAsync(OutputFormatterWriteContext context) { if (context == null) throw new ArgumentNullException(nameof(context)); var response = context.HttpContext.Response; response.ContentType = "video/mp4"; How to impelemnt ??? } }
并将以下行添加到Startup.cs
services.AddMvc(options => { options.OutputFormatters.Add(new VideoOutputFormatter()); });
它实际上调用我的自定义格式化程序
我不知道如何为video / mp4实现这个自定义媒体格式化程序.
有人可以帮帮我吗?
解决方法
查看Asp.NET Core的源代码真的帮助我找到了这个的答案.他们有一个
StreamOutputFormatter级别,非常接近您想要使用的级别.我只需要修改它来寻找PushStreamContent,它就像一个魅力.
这是我完整的VideoOutputFormatter:
public class VideoOutputFormatter : IOutputFormatter { public bool CanWriteResult(OutputFormatterCanWriteContext context) { if (context == null) throw new ArgumentNullException(nameof(context)); if (context.Object is PushStreamContent) return true; return false; } public async Task WriteAsync(OutputFormatterWriteContext context) { if (context == null) throw new ArgumentNullException(nameof(context)); using (var stream = ((PushStreamContent)context.Object)) { var response = context.HttpContext.Response; if (context.ContentType != null) { response.ContentType = context.ContentType.ToString(); } await stream.CopyToAsync(response.Body); } } }
您不希望将HttpResponseMessage包装在控制器中的ObjectResult中,而是将PushStreamContent对象推送到ObjectResult中.您仍然需要在ObjectResult上设置MediaTypeHeaderValue.
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