From 03c82169465d6d1b301d14828a730aba675503a9 Mon Sep 17 00:00:00 2001
From: dkanada <dkanada@users.noreply.github.com>
Date: Mon, 28 Dec 2020 13:38:04 +0900
Subject: [PATCH] Merge pull request #4860 from nyanmisaka/3ch-transcode-hls

Avoid transcoding to 3ch audio for HLS streaming

(cherry picked from commit 2913e2604c3a0fd36cf4d4f6d74a65289be187d5)
Signed-off-by: Joshua M. Boniface <joshua@boniface.me>
---
 .../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..efab87a38e 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
+                && state.TranscodingType != TranscodingJobType.Progressive
+                && resultChannels.HasValue
+                && (resultChannels.Value > 2 && resultChannels.Value < 6 || resultChannels.Value == 7))
+            {
+                resultChannels = 2;
+            }
+
             return resultChannels;
         }