Question

我一直在尝试在ASP.NET中设置MJPEG流。我想从URL检索MJEPG流，并将每个帧发送到每个连接的客户端。我能够找到的示例只能读取设置文件，而不是来自URL的连续流，并通过 MultiStreamContent 发送整个文件。由于我逐帧检索，我不能这样做。我想知道是否可以用ASP.NET MVC做我想做的事情。我目前正在使用AForge视频从链接中检索MJPEG流。我的控制器类代码：

using System.Net.Http;
using System.Web.Http;
using AForge.Video;

namespace VideoPrototypeMVC.Controllers
{
    public class CameraController : ApiController
    {
        int framecounter = 0;
        MJPEGStream stream = new MJPEGStream();

        [HttpGet]
        public void GetVideoContent()
        {   
            stream.Source = @"http://127.0.0.1:5002/stream";
            stream.NewFrame += new NewFrameEventHandler(showFrame);
            stream.Start();
            MultipartContent content = new MultipartContent();
            while (stream.IsRunning)
            {
            //Continues streaming should be here?
            }
        }

        //Can be used to display of a frame is available
        private void showFrame(object sender, NewFrameEventArgs eventArgs)
        {
            framecounter++;
            System.Diagnostics.Debug.WriteLine("New frame event: " + framecounter);

        }

        //Should be called at the end of the stream
        private void stopStream(object sender, ReasonToFinishPlaying reason)
        {
            System.Diagnostics.Debug.WriteLine("Stop stream");
            stream.Stop();
            framecounter = 0;
        }
    }
}

此代码不是最终版，但我只需要继续关闭。我找到了使用Socket servers的示例，但我想坚持MVC，因为它允许我更容易地设置服务器的其余部分。

Answer 1

确保其他人也可以使用此功能。我设法结合@Evk（再次感谢你）说的，以及我在这里找到的信息：creating my own MJPEG stream。

注意：下面的代码只是原型/概念验证！当我运行这个时，由于 StartStream 中无休止的循环，我的处理器拍摄到100％。将努力使这个更基于事件，但我认为下面的代码更容易解释。

fetching ip from: ip-api1
fetching ip from: broken_api
catched
Task was destroyed but it is pending!
task: <Task pending coro=<ThreadedResolver.resolve() running at /Volumes/external/venv/lib/python3.6/site-packages/aiohttp/resolver.py:31> wait_for=<Future pending cb=[_chain_future.<locals>._call_check_cancel() at /Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/asyncio/futures.py:408, <TaskWakeupMethWrapper object at 0x1038e2948>()]> cb=[shield.<locals>._done_callback() at /Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/asyncio/tasks.py:679]>
Task was destroyed but it is pending!
task: <Task pending coro=<get_ip() done, defined at ./run_7.py:15> wait_for=<Future pending cb=[<TaskWakeupMethWrapper object at 0x1038e23d8>()]>>

Answer 2

来自Arastelion的好答案，但是我注意到，如果您离开应用程序，那么后台仍然有一个正在处理的请求，这可能是资源浪费弹出stream.FlushAsync（）; stream.Close（）; stream.Dispose（）;在stopStream之后似乎可以解决该问题。

using System;
using System.IO;
using System.Net;
using System.Web;
using System.Net.Http;
using System.Web.Http;
using AForge.Video;
using System.Drawing;
using System.Text;
using System.Drawing.Imaging;
using System.Threading;

namespace VideoPrototypeMVC.Controllers
{
    public class CameraController : ApiController
    {
        private MJPEGStream mjpegStream = new MJPEGStream();
        private bool frameAvailable = false;
        private Bitmap frame = null;
        private string BOUNDARY = "frame";

        /// <summary>
        /// Initializer for the MJPEGstream
        /// </summary>
        CameraController()
        {
            mjpegStream.Source = @"{{INSERT STREAM URL}}";
            mjpegStream.NewFrame += new NewFrameEventHandler(showFrameEvent);
        }

        [HttpGet]
        public HttpResponseMessage GetVideoContent()
        {   
            mjpegStream.Start();
            var response = Request.CreateResponse();
            response.Content = new PushStreamContent((Action<Stream, HttpContent, TransportContext>)StartStream);
            response.Content.Headers.ContentType = System.Net.Http.Headers.MediaTypeHeaderValue.Parse("multipart/x-mixed-replace; boundary=" + BOUNDARY);
            return response;
        }

        /// <summary>
        /// Craete an appropriate header.
        /// </summary>
        /// <param name="length"></param>
        /// <returns></returns>
        private byte[] CreateHeader(int length)
        {
            string header =
                "--" + BOUNDARY + "\r\n" +
                "Content-Type:image/jpeg\r\n" +
                "Content-Length:" + length + "\r\n\r\n";

            return Encoding.ASCII.GetBytes(header);
        }

        public byte[] CreateFooter()
        {
            return Encoding.ASCII.GetBytes("\r\n");
        }

        /// <summary>
        /// Write the given frame to the stream
        /// </summary>
        /// <param name="stream">Stream</param>
        /// <param name="frame">Bitmap format frame</param>
        private void WriteFrame(Stream stream, Bitmap frame)
        {
            // prepare image data
            byte[] imageData = null;

            // this is to make sure memory stream is disposed after using
            using (MemoryStream ms = new MemoryStream())
            {
                frame.Save(ms, ImageFormat.Jpeg);
                imageData = ms.ToArray();
            }

            // prepare header
            byte[] header = CreateHeader(imageData.Length);
            // prepare footer
            byte[] footer = CreateFooter();

            // Start writing data
            stream.Write(header, 0, header.Length);
            stream.Write(imageData, 0, imageData.Length);
            stream.Write(footer, 0, footer.Length);
        }

        /// <summary>
        /// While the MJPEGStream is running and clients are connected,
        /// continue sending frames.
        /// </summary>
        /// <param name="stream">Stream to write to.</param>
        /// <param name="httpContent">The content information</param>
        /// <param name="transportContext"></param>
        private void StartStream(Stream stream, HttpContent httpContent, TransportContext transportContext)
        {
            while (mjpegStream.IsRunning && HttpContext.Current.Response.IsClientConnected)
            {
                if (frameAvailable)
                {
                    try
                    {
                        WriteFrame(stream, frame);
                        frameAvailable = false;
                    } catch (Exception e)
                    {
                        System.Diagnostics.Debug.WriteLine(e);
                    }
                }else
                {
                    Thread.Sleep(30);
                }
            }
            stopStream();
            stream.FlushAsync();
            stream.Close();
            stream.Dispose();
        }

        /// <summary>
        /// This event is thrown when a new frame is detected by the MJPEGStream
        /// </summary>
        /// <param name="sender">Object that is sending the event</param>
        /// <param name="eventArgs">Data from the event, including the frame</param>
        private void showFrameEvent(object sender, NewFrameEventArgs eventArgs)
        {
            frame = new Bitmap(eventArgs.Frame);
            frameAvailable = true;
        }

        /// <summary>
        /// Stop the stream.
        /// </summary>
        private void stopStream()
        {
            System.Diagnostics.Debug.WriteLine("Stop stream");
            mjpegStream.Stop();
        }

         protected override void Dispose(bool disposing)
         {
            if (disposing)
             {
                 stopStream();
             }

             base.Dispose(disposing);
           } 


    }
}

使用C＃/ ASP.NET MVC逐帧MJPEG流式传输

2 个答案: