c# - 为什么当我尝试使用 directshow 将视频捕捉到 mp4 文件时，文件是空的？

Question

当我退出程序时，mp4 文件会自动删除。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using DirectShowLib;
using DirectShowLib.BDA;
using DirectShowLib.DES;
using DirectShowLib.DMO;
using DirectShowLib.Dvd;
using DirectShowLib.MultimediaStreaming;
using DirectShowLib.SBE;
using System.Runtime.InteropServices;
using System.Management;
using System.IO;
using AForge.Video;
using AForge.Video.DirectShow;
using AForge.Video.FFMPEG;
using AForge.Video.VFW;
using System.Drawing.Imaging;


namespace Youtube_Manager
{

    public partial class Elgato_Video_Capture : Form
    {
        IFileSinkFilter sink;

        IFilterGraph2 graph;
        ICaptureGraphBuilder2 captureGraph;
        Size videoSize;
        string error = "";
        List<Object> devices = new List<Object>();
        IMediaControl mediaControl;

        public Elgato_Video_Capture()
        {
            InitializeComponent();

            if (comboBox1.Items.Count == 0)
            {
                for (int xx = 1; xx <= 8; xx++)
                {
                    comboBox1.Items.Add(xx);
                }
            }

            InitDevice();

        }

        IPin outPin;
        IPin inPin;
        private void InitDevice()
        {
            try
            {
                //Set the video size to use for capture and recording
                videoSize = new Size(827, 505);//1280, 720);

                //Initialize filter graph and capture graph
                graph = (IFilterGraph2)new FilterGraph();
                captureGraph = (ICaptureGraphBuilder2)new CaptureGraphBuilder2();
                captureGraph.SetFiltergraph(graph);
                //Create filter for Elgato
                Guid elgatoGuid = new Guid("39F50F4C-99E1-464A-B6F9-D605B4FB5918");
                Type comType = Type.GetTypeFromCLSID(elgatoGuid);
                IBaseFilter  elgatoFilter = (IBaseFilter)Activator.CreateInstance(comType);
                graph.AddFilter(elgatoFilter, "Elgato Video Capture Filter");

                //Create smart tee filter, add to graph, connect Elgato's video out to smart tee in
                IBaseFilter smartTeeFilter = (IBaseFilter)new SmartTee();

                graph.AddFilter(smartTeeFilter, "Smart Tee");
                outPin = GetPin(elgatoFilter, "Video");
                inPin = GetPin(smartTeeFilter, "Input");               

                graph.Connect(outPin, inPin);

                //Create video renderer filter, add it to graph, connect smartTee Preview pin to video renderer's input pin
                IBaseFilter videoRendererFilter = (IBaseFilter)new VideoRenderer();

                graph.AddFilter(videoRendererFilter, "Video Renderer");
                outPin = GetPin(smartTeeFilter, "Capture");

                inPin = GetPin(videoRendererFilter, "Input");
                graph.Connect(outPin, inPin);

                captureGraph.SetOutputFileName(MediaSubType.Avi, @"e:\screenshots\test1.mp4", out smartTeeFilter, out sink);
                sink.SetFileName(@"e:\screenshots\test1.mp4", null);

                //Render stream from video renderer
                captureGraph.RenderStream(PinCategory.Capture, MediaType.Video, videoRendererFilter, null, null);
                //Set the video preview to be the videoFeed panel
                IVideoWindow vw = (IVideoWindow)graph;
                vw.put_Owner(pictureBox1.Handle);
                vw.put_MessageDrain(this.Handle);
                vw.put_WindowStyle(WindowStyle.Child | WindowStyle.ClipSiblings | WindowStyle.ClipChildren);
                vw.SetWindowPosition(0, 0, 827, 505);

                //Start the preview
                mediaControl = graph as IMediaControl;
                mediaControl.Run();

            }
            catch (Exception err)
            {
                error = err.ToString();
            }
        }

         IPin GetPin(IBaseFilter filter, string pinname)
        {
            IEnumPins epins;
            int hr = filter.EnumPins(out epins);
            checkHR(hr, "Can't enumerate pins");
            IntPtr fetched = Marshal.AllocCoTaskMem(4);
            IPin[] pins = new IPin[1];
            while (epins.Next(1, pins, fetched) == 0)
            {
                PinInfo pinfo;
                pins[0].QueryPinInfo(out pinfo);
                bool found = (pinfo.name == pinname);
                DsUtils.FreePinInfo(pinfo);
                if (found)
                    return pins[0];
            }
            checkHR(-1, "Pin not found");
            return null;
        }

        public  void checkHR(int hr, string msg)
        {
            if (hr < 0)
            {
                MessageBox.Show(msg);
                DsError.ThrowExceptionForHR(hr);
            }            
        }
}

我现在将这部分添加到我的代码中:

captureGraph.SetOutputFileName(MediaSubType.Avi, @"e:\screenshots\test1.mp4", out smartTeeFilter, out sink);
sink.SetFileName(@"e:\screenshots\test1.mp4", null);

我看到了预览，但 mp4 文件是空的，它根本没有将视频保存到文件中。我想做的是使用 directshow 将视频流保存到 mp4 文件。现在我只能在 pictureBox 中看到视频的预览。

Answer 1

1. 您捕获的不是 MP4 文件，而是仅带有 MP4 扩展名的 AVI 文件! DirectShow 没有原生的 MP4-Mux。您需要像 GDCL MP4 Mux 一样单独安装一个.

2. 我认为您的连接工作不正常。使用 DirectShowNet，您需要检查返回码，然后自己抛出异常，例如:

   int hr = graph.Connect(outPin, inPin);;
   DsError.ThrowExceptionForHR(hr);
   

3. 您的 captureGraph.RenderStream 没有用，因为 VideoRender-Filter 没有输出引脚。请看meaning of this function .您可以仅使用 RenderStream 更好地构建此图，它甚至会为您插入 SmartTee-Filter。