From bc6ec08322a6d9111849dd4661bdda3746347835 Mon Sep 17 00:00:00 2001
From: nyanmisaka <nst799610810@gmail.com>
Date: Thu, 24 Dec 2020 19:41:02 +0800
Subject: [PATCH] avoid transcoding to 3ch audio for HLS streaming

---
 .../MediaEncoding/EncodingHelper.cs                    | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs b/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
index 6667c1c3bc..17201551a0 100644
--- a/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
+++ b/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
@@ -1722,6 +1722,16 @@ namespace MediaBrowser.Controller.MediaEncoding
                     : transcoderChannelLimit.Value;
             }
 
+            // Avoid transcoding to audio channels other than 1ch, 2ch, 6ch (5.1 layout) and 8ch (7.1 layout).
+            // https://developer.apple.com/documentation/http_live_streaming/hls_authoring_specification_for_apple_devices
+            if (isTranscodingAudio
+                && resultChannels.HasValue
+                && resultChannels.Value > 2
+                && resultChannels.Value < 6)
+            {
+                resultChannels = 2;
+            }
+
             return resultChannels;
         }