ASP.Net Core Web Api中的异步视频流不起作用

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

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.

（编辑：安卓应用网）

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