diff --git a/Jellyfin.Api/Controllers/DynamicHlsController.cs b/Jellyfin.Api/Controllers/DynamicHlsController.cs
index 329dd2c4cb..130c1192f7 100644
--- a/Jellyfin.Api/Controllers/DynamicHlsController.cs
+++ b/Jellyfin.Api/Controllers/DynamicHlsController.cs
@@ -1733,7 +1733,7 @@ public class DynamicHlsController : BaseJellyfinApiController
var channels = state.OutputAudioChannels;
- var useDownMixAlgorithm = state.AudioStream.Channels is 6 && _encodingOptions.DownMixStereoAlgorithm != DownMixStereoAlgorithms.None;
+ var useDownMixAlgorithm = DownMixAlgorithmsHelper.AlgorithmFilterStrings.ContainsKey((_encodingOptions.DownMixStereoAlgorithm, DownMixAlgorithmsHelper.InferChannelLayout(state.AudioStream)));
if (channels.HasValue
&& (channels.Value != 2
diff --git a/MediaBrowser.Controller/MediaEncoding/DownMixAlgorithmsHelper.cs b/MediaBrowser.Controller/MediaEncoding/DownMixAlgorithmsHelper.cs
new file mode 100644
index 0000000000..b90f9a4793
--- /dev/null
+++ b/MediaBrowser.Controller/MediaEncoding/DownMixAlgorithmsHelper.cs
@@ -0,0 +1,65 @@
+using System.Collections.Generic;
+using MediaBrowser.Model.Entities;
+
+namespace MediaBrowser.Controller.MediaEncoding;
+
+///
+/// Describes the downmix algorithms capabilities.
+///
+public static class DownMixAlgorithmsHelper
+{
+ ///
+ /// The filter string of the DownMixStereoAlgorithms.
+ /// The index is the tuple of (algorithm, layout).
+ ///
+ public static readonly Dictionary<(DownMixStereoAlgorithms, string), string> AlgorithmFilterStrings = new()
+ {
+ { (DownMixStereoAlgorithms.Dave750, "5.1"), "pan=stereo|c0=0.5*c2+0.707*c0+0.707*c4+0.5*c3|c1=0.5*c2+0.707*c1+0.707*c5+0.5*c3" },
+ { (DownMixStereoAlgorithms.NightmodeDialogue, "5.1"), "pan=stereo|c0=c2+0.30*c0+0.30*c4|c1=c2+0.30*c1+0.30*c5" },
+ { (DownMixStereoAlgorithms.Rfc7845, "3.0"), "pan=stereo|c0=0.414214*c2+0.585786*c0|c1=0.414214*c2+0.585786*c1" },
+ { (DownMixStereoAlgorithms.Rfc7845, "quad"), "pan=stereo|c0=0.422650*c0+0.366025*c2+0.211325*c3|c1=0.422650*c1+0.366025*c3+0.211325*c2" },
+ { (DownMixStereoAlgorithms.Rfc7845, "5.0"), "pan=stereo|c0=0.460186*c2+0.650802*c0+0.563611*c3+0.325401*c4|c1=0.460186*c2+0.650802*c1+0.563611*c4+0.325401*c3" },
+ { (DownMixStereoAlgorithms.Rfc7845, "5.1"), "pan=stereo|c0=0.374107*c2+0.529067*c0+0.458186*c4+0.264534*c5+0.374107*c3|c1=0.374107*c2+0.529067*c1+0.458186*c5+0.264534*c4+0.374107*c3" },
+ { (DownMixStereoAlgorithms.Rfc7845, "6.1"), "pan=stereo|c0=0.321953*c2+0.455310*c0+0.394310*c5+0.227655*c6+0.278819*c4+0.321953*c3|c1=0.321953*c2+0.455310*c1+0.394310*c6+0.227655*c5+0.278819*c4+0.321953*c3" },
+ { (DownMixStereoAlgorithms.Rfc7845, "7.1"), "pan=stereo|c0=0.274804*c2+0.388631*c0+0.336565*c6+0.194316*c7+0.336565*c4+0.194316*c5+0.274804*c3|c1=0.274804*c2+0.388631*c1+0.336565*c7+0.194316*c6+0.336565*c5+0.194316*c4+0.274804*c3" },
+ };
+
+ ///
+ /// Get the audio channel layout string from the audio stream
+ /// If the input audio string does not have a valid layout string, guess from channel count.
+ ///
+ /// The audio stream to get layout.
+ /// Channel Layout string.
+ public static string InferChannelLayout(MediaStream audioStream)
+ {
+ if (!string.IsNullOrWhiteSpace(audioStream.ChannelLayout))
+ {
+ // Note: BDMVs do not derive this string from ffmpeg, which would cause ambiguity with 4-channel audio
+ // "quad" => 2 front and 2 rear, "4.0" => 3 front and 1 rear
+ // BDMV will always use "4.0" in this case
+ // Because the quad layout is super rare in BDs, we will use "4.0" as is here
+ return audioStream.ChannelLayout;
+ }
+
+ if (audioStream.Channels is null)
+ {
+ return string.Empty;
+ }
+
+ // When we don't have definitive channel layout, we have to guess from the channel count
+ // Guessing is not always correct, but for most videos we don't have to guess like this as the definitive layout is recorded during scan
+ var inferredLayout = audioStream.Channels.Value switch
+ {
+ 1 => "mono",
+ 2 => "stereo",
+ 3 => "2.1", // Could also be 3.0, prefer 2.1
+ 4 => "4.0", // Could also be quad (with rear left and rear right) and 3.1 with LFE. prefer 4.0 with front center and back center
+ 5 => "5.0",
+ 6 => "5.1", // Could also be 6.0 or hexagonal, prefer 5.1
+ 7 => "6.1", // Could also be 7.0, prefer 6.1
+ 8 => "7.1", // Could also be 8.0, prefer 7.1
+ _ => string.Empty // Return empty string for not supported layout
+ };
+ return inferredLayout;
+ }
+}
diff --git a/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs b/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
index 42b09a29e7..2c3d44bf83 100644
--- a/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
+++ b/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
@@ -2666,28 +2666,17 @@ namespace MediaBrowser.Controller.MediaEncoding
var filters = new List();
- if (channels.HasValue
- && channels.Value == 2
- && state.AudioStream is not null
- && state.AudioStream.Channels.HasValue
- && state.AudioStream.Channels.Value == 6)
+ if (channels is 2 && state.AudioStream?.Channels is > 2)
{
- if (!encodingOptions.DownMixAudioBoost.Equals(1))
+ var hasDownMixFilter = DownMixAlgorithmsHelper.AlgorithmFilterStrings.TryGetValue((encodingOptions.DownMixStereoAlgorithm, DownMixAlgorithmsHelper.InferChannelLayout(state.AudioStream)), out var downMixFilterString);
+ if (hasDownMixFilter)
{
- filters.Add("volume=" + encodingOptions.DownMixAudioBoost.ToString(CultureInfo.InvariantCulture));
+ filters.Add(downMixFilterString);
}
- switch (encodingOptions.DownMixStereoAlgorithm)
+ if (!encodingOptions.DownMixAudioBoost.Equals(1))
{
- case DownMixStereoAlgorithms.Dave750:
- filters.Add("pan=stereo|c0=0.5*c2+0.707*c0+0.707*c4+0.5*c3|c1=0.5*c2+0.707*c1+0.707*c5+0.5*c3");
- break;
- case DownMixStereoAlgorithms.NightmodeDialogue:
- filters.Add("pan=stereo|c0=c2+0.30*c0+0.30*c4|c1=c2+0.30*c1+0.30*c5");
- break;
- case DownMixStereoAlgorithms.None:
- default:
- break;
+ filters.Add("volume=" + encodingOptions.DownMixAudioBoost.ToString(CultureInfo.InvariantCulture));
}
}
@@ -7008,7 +6997,10 @@ namespace MediaBrowser.Controller.MediaEncoding
var channels = state.OutputAudioChannels;
- if (channels.HasValue && ((channels.Value != 2 && state.AudioStream?.Channels != 6) || encodingOptions.DownMixStereoAlgorithm == DownMixStereoAlgorithms.None))
+ var useDownMixAlgorithm = state.AudioStream is not null
+ && DownMixAlgorithmsHelper.AlgorithmFilterStrings.ContainsKey((encodingOptions.DownMixStereoAlgorithm, DownMixAlgorithmsHelper.InferChannelLayout(state.AudioStream)));
+
+ if (channels.HasValue && !useDownMixAlgorithm)
{
args += " -ac " + channels.Value;
}
diff --git a/MediaBrowser.Model/Entities/DownMixStereoAlgorithms.cs b/MediaBrowser.Model/Entities/DownMixStereoAlgorithms.cs
index 385cd6a34e..be43ef32d3 100644
--- a/MediaBrowser.Model/Entities/DownMixStereoAlgorithms.cs
+++ b/MediaBrowser.Model/Entities/DownMixStereoAlgorithms.cs
@@ -19,5 +19,10 @@ public enum DownMixStereoAlgorithms
///
/// Nightmode Dialogue algorithm.
///
- NightmodeDialogue = 2
+ NightmodeDialogue = 2,
+
+ ///
+ /// RFC7845 Section 5.1.1.5 defined algorithm.
+ ///
+ Rfc7845 = 3
}