Add stereo downmix algorithm selection.

MediaBrowser.Model/Entities/DownMixStereoAlgorithms.cs

@@ -0,0 +1,23 @@
+namespace MediaBrowser.Model.Entities;
+
+/// <summary>
+/// An enum representing an algorithm to downmix 6ch+ to stereo.
+/// Algorithms sourced from https://superuser.com/questions/852400/properly-downmix-5-1-to-stereo-using-ffmpeg/1410620#1410620.
+/// </summary>
+public enum DownMixStereoAlgorithms
+{
+    /// <summary>
+    /// No special algorithm.
+    /// </summary>
+    None = 0,
+
+    /// <summary>
+    /// Algorithm by Dave_750.
+    /// </summary>
+    Dave750 = 1,
+
+    /// <summary>
+    /// Nightmode Dialogue algorithm.
+    /// </summary>
+    NightmodeDialogue = 2
+}