ASP.Net Core Web Api中的异步视频流无法正常工作
我以前使用过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而言,这种方式无法按预期工作。
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, 0, Math.Min(length, buffer.Length));
await outputStream.WriteAsync(buffer, 0, 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没有内置媒体格式化器,用于video / mp4我已经创建了以下自定义媒体格式器
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 我不知道如何实现这个视频/ MP4的自定义媒体格式。 任何人都可以帮助我?
查看Asp.NET Core的源代码确实帮助我找到了这个答案。 他们有一个StreamOutputFormatter类,它非常接近你想要使用的类。 我只需修改它就可以查找PushStreamContent
并且它的功能就像一个魅力一样。
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);
}
}
}
与其将HttpResponseMessage
封装在控制器的ObjectResult
中, PushStreamContent
将PushStreamContent
对象转移到ObjectResult
。 您仍然需要在ObjectResult
上设置MediaTypeHeaderValue
。
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