ASP.NET Core mvc应用程序中的FFMPEG记录

Question

我正在使用ASP.NET Core和ffmpeg来录制实时视频流。当页面收到get请求时，流应开始记录并使用ffmpeg保存到文件夹。我要这样做，以便在访问stop端点时，ffmpeg进程完全关闭。

不幸的是，离开Get方法后，我无法向stdin发送'q'。使用taskkill需要使用/ F来使ffmpeg进程（不是窗口）强制退出并且无法正确保存视频，从而导致文件损坏。

我尝试使用Process.Kill()，但也会导致文件损坏。另外，我尝试了Process.CloseMainWindow()可以正常工作，但仅当进程作为窗口启动时，并且无法在正在使用的服务器中作为窗口启动进程。

我将下面提供的代码包括在内，希望有人可以引导我走上正确的道路。

using System;
...
using Microsoft.Extensions.Logging;

namespace MyApp.Controllers
{
    [Route("api/[controller]")]
    [Authorize]
    public class RecordingController : Controller
    {
        private readonly ApplicationDbContext _context;
        private readonly ILogger<HomeController> _logger;

        public RecordingController(ApplicationDbContext context, ILogger<HomeController> logger)
        {
            _context = context;
            _logger = logger;
        }

        [HttpGet]
        public async Task<ActionResult> Get()
        {

            // Define the os process
            var processStartInfo = new ProcessStartInfo()
            {
                // ffmpeg arguments
                Arguments = "-f mjpeg -i \"https://urlofstream.com/video.gci\" -r 5 \"wwwroot/video.mp4\"",
                FileName = "ffmpeg.exe",
                UseShellExecute = true
            };

            var p1 = Process.Start(processStartInfo);

            // p1.StandardInput.WriteLineAsync("q"); <-- This works here but not in the Stop method

            return Ok(p1.Id);
        }


        // GET: api/Recording/stop
        [HttpGet("stop/{pid}")]
        public ActionResult Stop(int pid)
        {
            Process processes = Process.GetProcessById(pid);
            processes.StandardInput.WriteLineAsync("q");     // Does not work, is not able to redirect input
            return Ok();
        }
    }
}

Answer 1

我已经找到了解决此问题的方法，希望可以对其他人有所帮助。解决方案是结合使用Singleton和ConcurrentDictionary并将其写入StandardInput。可以写入正在运行的进程的标准输入的唯一方法是，如果您仍然有权访问已启动的Process句柄，并且您将无法从控制器内部对其进行访问，那么您将需要创建一个Singleton并存储进程在ConcurrentDictionary中（非常适合从多个线程进行更新）。

[首先，我创建了一个录音管理器类。 RecordingManager.cs

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Threading.Tasks;

namespace MyApp.Services
{
    public class RecordingManager
    {
        // Key int is the ProcessId. Value process is the running Process
        private static ConcurrentDictionary<int, Process> _processes = new ConcurrentDictionary<int, Process>();

        public Process Start()
        {
            // Define the os process
            var processStartInfo = new ProcessStartInfo()
            {
                // ffmpeg arguments
                Arguments = "-f mjpeg -i https://urlofstream.com/video.gci -r 5 wwwroot/video.mp4",
                FileName = "ffmpeg.exe",
                RedirectStandardInput = true, // Must be set to true
                UseShellExecute = false       // Must be set to false
            };

            Process p = Process.Start(processStartInfo);

            // Add the Process to the Dictionary with Key: Process ID and value as the running process
            _processes.TryAdd(p1.Id, p);

            return p;
        }

        private Process GetProcessByPid(int pid)
        {
            return _processes.FirstOrDefault(p => p.Key == pid).Value;
        }

        public void Stop(int pid)
        {
            Process p = GetProcessByPid(pid);

            // FFMPEG Expects a q written to the STDIN to stop the process
            p.StandardInput.WriteLine("q\n");
            _processes.TryRemove(pid, out p);

            // Free up resources
            p.Close()
        }
    }
}

接下来，我将单例添加到ConfigureServices方法中的startup.cs类中

services.AddSingleton<RecordingManager>();

最后，我将单例添加到控制器构造函数中，并在其中调用方法。 RecordingController.cs

namespace MyApp.Controllers
{
    [Route("api/[controller]")]
    [Authorize]
    public class RecordingController : Controller
    {
        private readonly ApplicationDbContext _context;
        private readonly ILogger<HomeController> _logger;
        private readonly RecordingManager _recordingManager;

        public RecordingController(ApplicationDbContext context, ILogger<HomeController> logger, RecordingManager recordingManager)
        {
            _context = context;
            _logger = logger;
            _recordingManager = recordingManager;
        }

        [HttpGet]
        public async Task<ActionResult> Get()
        {
            Process p = _recordingManager.Start();
            return Ok(p.Id); // Wouldn't recommend simply returning an Ok Result here. Check for issues
        }


        // GET: api/Recording/stop
        [HttpGet("stop/{pid}")]
        public ActionResult Stop(int pid)
        {
            _recordingManager.Stop(pid);
            return Ok(); // Wouldn't recommend simply returning an Ok Result here. Check for issues
        }
    }
}