Use nullable enum type instead of strings

Jellyfin.Api/Helpers/TranscodingJobHelper.cs

@@ -444,8 +444,10 @@ namespace Jellyfin.Api.Helpers
             {
                 var audioCodec = state.ActualOutputAudioCodec;
                 var videoCodec = state.ActualOutputVideoCodec;
-                var hardwareAccelerationType = _serverConfigurationManager.GetEncodingOptions().HardwareAccelerationType;
-                hardwareAccelerationType = string.IsNullOrEmpty(hardwareAccelerationType) ? "none" : hardwareAccelerationType;
+                var hardwareAccelerationTypeString = _serverConfigurationManager.GetEncodingOptions().HardwareAccelerationType;
+                HardwareEncodingType? hardwareAccelerationType = string.IsNullOrEmpty(hardwareAccelerationTypeString)
+                    ? null
+                    : (HardwareEncodingType)Enum.Parse(typeof(HardwareEncodingType), hardwareAccelerationTypeString, true);
 
                 _sessionManager.ReportTranscodingInfo(deviceId, new TranscodingInfo
                 {

MediaBrowser.Model/Session/HardwareEncodingType.cs

@@ -0,0 +1,48 @@
+namespace MediaBrowser.Model.Session
+{
+    /// <summary>
+    /// Enum HardwareEncodingType.
+    /// </summary>
+    public enum HardwareEncodingType
+    {
+        /// <summary>
+        /// AMD AMF
+        /// </summary>
+        AMF,
+
+        /// <summary>
+        /// Intel Quick Sync Video
+        /// </summary>
+        QSV,
+
+        /// <summary>
+        /// NVIDIA NVENC
+        /// </summary>
+        NVENC,
+
+        /// <summary>
+        /// OpenMax OMX
+        /// </summary>
+        OMX,
+
+        /// <summary>
+        /// Exynos V4L2 MFC
+        /// </summary>
+        V4L2M2M,
+
+        /// <summary>
+        /// MediaCodec Android
+        /// </summary>
+        MediaCodec,
+
+        /// <summary>
+        /// Video Acceleration API (VAAPI)
+        /// </summary>
+        VAAPI,
+
+        /// <summary>
+        /// Video ToolBox
+        /// </summary>
+        VideoToolBox
+    }
+}

MediaBrowser.Model/Session/TranscodingInfo.cs

@@ -34,7 +34,7 @@ namespace MediaBrowser.Model.Session
 
         public int? AudioChannels { get; set; }
 
-        public string HardwareAccelerationType { get; set; }
+        public HardwareEncodingType? HardwareAccelerationType { get; set; }
 
         public TranscodeReason[] TranscodeReasons { get; set; }
     }