WebAPI PushStreamContent 客户端读取视频流答案

【问题标题】：WebAPI PushStreamContent client read video streamWebAPI PushStreamContent 客户端读取视频流
【发布时间】：2019-06-12 13:14:26
【问题描述】：

我有一个通过 webapi 公开的相机。此相机返回 jpeg 帧。在服务器端，我使用以下方法：

[Route("api/v1/camera/live/stream")]
[HttpGet]
public HttpResponseMessage GetStream()
{
    logger.Trace($"GET api/v1/camera/live/stream called");

    var response = Request.CreateResponse(HttpStatusCode.PartialContent);
    response.Content = new PushStreamContent(new Action<Stream, HttpContent, TransportContext>(async (stream, content, tansportContext) =>
    {
        EventHandler<AcquiredDataEventArgs<CameraFrame>> handler = (_, __) => { };
        try
        {
            MjpegWriter writer = new MjpegWriter(stream);
            handler = (s, e) => writer.Write(e.Data.Image.GetJpegStream());

            camera.DataAcquired += handler;
            while (HttpContext.Current.Response.IsClientConnected)
            {
                await Task.Delay(100);
            }
            camera.DataAcquired -= handler;
        }
        catch (Exception ex)
        {
            logger.Error($"Streaming error", ex);
            throw;
        }
        logger.Trace("streaming ended");

    }));

    response.Content.Headers.ContentType = MediaTypeHeaderValue.Parse("multipart/x-mixed-replace; boundary=--boundary");

    return response;
}

我想在 WPF 应用程序中实时显示此视频流。如果我通过网络浏览器打开视频流，它可以很好地流式传输视频......但是我如何流式传输到 c# 客户端应用程序？

【问题讨论】：

标签： c# asp.net-web-api video-streaming

【解决方案1】：

您可以为此使用 HttpClient。只要确保你没有通过设置HttpCompletionOption.ResponseHeadersRead来缓冲响应。

using (var httpClient = new HttpClient())
using (var response = await httpClient.GetAsync("http://...",
    HttpCompletionOption.ResponseHeadersRead))
using (Stream stream = await response.Content.ReadAsStreamAsync())
{
    // Do whatever with the resulting stream.
}

【讨论】：

【解决方案2】：

Lib（可通过 nuget 获得）Emgu.CV 是 OpenCV 上的 C# 包装器，可以接收流。

using Emgu.CV;

...

    private void StartWatching()
    {
        Task.Run(() =>
        {
            try
            {
                capture = new VideoCapture(headConfiguration.CameraStreamingUri.ToString());
                capture.ImageGrabbed += Capture_ImageGrabbed;
                capture.Start(ExceptionHandler.AlwaysHandle);
            }
            catch (Exception ex)
            {
                capture = null;
                Logger.Error(ex);
                throw ex;
            }
        });
    }

    private void Capture_ImageGrabbed(object sender, EventArgs e)
    {
        if (capture == null || OnNewCameraFrame == null)
        {
            return;
        }

        try
        {
            var frame = new Mat();
            if (capture.Retrieve(frame))
            {
                var output = new ByteImage(frame.Width, frame.Height, frame.Step);

                Marshal.Copy(frame.DataPointer, output.Data, 0, output.Height * output.Stride);

                OnNewCameraFrame?.Invoke(this, new ValueChangeArgs<ByteImage>(output));
            }
        }
        catch (Exception ex)
        {
            Logger.Error(ex);
        }
    }

【讨论】：