a hack to unconditionally kill ffmpeg when parent .NET process exits

FFMpegCore/Extend/Job.cs

@@ -0,0 +1,46 @@
+using System;
+using System.Runtime.InteropServices;
+
+using static PInvoke.Kernel32;
+
+
+namespace FFMpegCore.Extend {
+    public class Job : IDisposable {
+        readonly SafeObjectHandle handle;
+
+        public Job() {
+            this.handle = CreateJobObject(IntPtr.Zero, null);
+
+            var info = new JOBOBJECT_BASIC_LIMIT_INFORMATION {
+                LimitFlags = JOB_OBJECT_LIMIT_FLAGS.JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE,
+            };
+
+            var extendedInfo = new JOBOBJECT_EXTENDED_LIMIT_INFORMATION { BasicLimitInformation = info };
+
+            int length = Marshal.SizeOf(typeof(JOBOBJECT_EXTENDED_LIMIT_INFORMATION));
+            IntPtr extendedInfoPtr = Marshal.AllocHGlobal(length);
+            Marshal.StructureToPtr(extendedInfo, extendedInfoPtr, false);
+
+            if (!SetInformationJobObject(this.handle, JOBOBJECTINFOCLASS.JobObjectExtendedLimitInformation, extendedInfoPtr, (uint)length))
+                throw new System.ComponentModel.Win32Exception();
+        }
+
+        public bool AddProcess(SafeObjectHandle processHandle) {
+            return AssignProcessToJobObject(this.handle, processHandle);
+        }
+
+        #region IDisposable Members
+
+        public void Dispose() {
+            this.Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+
+        private void Dispose(bool disposing) => this.Close();
+
+        public void Close() => this.handle.Close();
+
+        #endregion
+    }
+}

FFMpegCore/FFMpeg/FFMpegArgumentProcessor.cs

@@ -9,6 +9,12 @@
 using System.Threading;
 using System.Threading.Tasks;
 using FFMpegCore.Enums;
+using FFMpegCore.Exceptions;
+using FFMpegCore.Extend;
+using FFMpegCore.Helpers;
+using Instances;
+
+using PInvoke;
 
 namespace FFMpegCore
 {
@@ -141,7 +147,14 @@ private async Task<IProcessResult> Process(ProcessArguments processArguments, Ca
 
             _ffMpegArguments.Pre();
 
-            using var instance = processArguments.Start();
+            using var instance = (ProcessInstance)processArguments.Start();
+            
+            using var job = new Job();
+            var processHack = (Process)typeof(ProcessInstance).GetField("_process", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance)
+                .GetValue(instance);
+            using var instanceHandle = new Kernel32.SafeObjectHandle(processHack.Handle, ownsHandle: false);
+            job.AddProcess(instanceHandle);
+            
             var cancelled = false;
             void OnCancelEvent(object sender, int timeout)
             {

FFMpegCore/FFMpegCore.csproj

@@ -17,6 +17,7 @@
 
     <ItemGroup>
         <PackageReference Include="Instances" Version="3.0.0"/>
+        <PackageReference Include="PInvoke.Kernel32" Version="0.7.104" />
         <PackageReference Include="System.Text.Json" Version="7.0.1"/>
     </ItemGroup>