RecordingExtensions.cs

using System;
using System.Reflection;
using UnityEngine;

/// Access Unity.Recorder window through reflection
public static class RecordingExtensions
{
    /// Start recording video using settings from the Recorder window
    public static void StartRecording() => StartStopRecording("StartRecording");
    
    /// Stop the Recorder window recording
    public static void StopRecording() => StartStopRecording("StopRecording");
    
    /// Returns true if the Recorder window is recording
    public static bool isRecording
    {
        get
        {
            if (recorderWindowType == null) // Not running in editor
                return false;

            var windows = Resources.FindObjectsOfTypeAll(recorderWindowType);
            for (int i = 0; i < windows.Length; ++i)
            {
                var window = windows[i];
                if ((bool)isRecordingMethod.Invoke(window, new object[0]))
                    return true;
            }

            return false;
        }
    }

    static Type recorderWindowType => _recorderWindowType.Value;
    static Lazy<Type> _recorderWindowType = new Lazy<Type>(() =>
        Type.GetType("UnityEditor.Recorder.RecorderWindow, Unity.Recorder.Editor, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null"));

    static MethodInfo isRecordingMethod => _isRecordingMethod.Value;
    static Lazy<MethodInfo> _isRecordingMethod = new Lazy<MethodInfo>(() =>
        recorderWindowType.GetMethod("IsRecording", BindingFlags.Instance | BindingFlags.Public));

    static void StartStopRecording(string methodName)
    {
        Debug.Log($"[RECORDER] {methodName}");
        if (recorderWindowType == null)
            return;

        var getWindowMethod = recorderWindowType.BaseType.GetMethod("GetWindow", BindingFlags.Static | BindingFlags.Public, null, new Type[] { typeof(Type) }, null);
        var recorderWindow = getWindowMethod.Invoke(null, new object[] { recorderWindowType });
        var startStopMethod = recorderWindowType.GetMethod(methodName);
        startStopMethod.Invoke(recorderWindow, new object[0]);
    }
}