Merge pull request #11492 from jellyfin/better-vbr-settings

Add better audio VBR settings

1 files changed, 25 insertions, 12 deletions

diff --git a/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs b/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
index 98351377e..42b09a29e 100644
--- a/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
+++ b/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
@@ -2606,8 +2606,9 @@ namespace MediaBrowser.Controller.MediaEncoding
             return 128000 * (outputAudioChannels ?? audioStream.Channels ?? 2);
         }
 
-        public string GetAudioVbrModeParam(string encoder, int bitratePerChannel)
+        public string GetAudioVbrModeParam(string encoder, int bitrate, int channels)
         {
+            var bitratePerChannel = bitrate / Math.Max(channels, 1);
             if (string.Equals(encoder, "libfdk_aac", StringComparison.OrdinalIgnoreCase))
             {
                 return " -vbr:a " + bitratePerChannel switch
@@ -2622,14 +2623,26 @@ namespace MediaBrowser.Controller.MediaEncoding
 
             if (string.Equals(encoder, "libmp3lame", StringComparison.OrdinalIgnoreCase))
             {
-                return " -qscale:a " + bitratePerChannel switch
+                // lame's VBR is only good for a certain bitrate range
+                // For very low and very high bitrate, use abr mode
+                if (bitratePerChannel is < 122500 and > 48000)
                 {
-                    < 48000 => "8",
-                    < 64000 => "6",
-                    < 88000 => "4",
-                    < 112000 => "2",
-                    _ => "0"
-                };
+                    return " -qscale:a " + bitratePerChannel switch
+                    {
+                        < 64000 => "6",
+                        < 88000 => "4",
+                        < 112000 => "2",
+                        _ => "0"
+                    };
+                }
+
+                return " -abr:a 1" + " -b:a " + bitrate;
+            }
+
+            if (string.Equals(encoder, "aac_at", StringComparison.OrdinalIgnoreCase))
+            {
+                // aac_at's CVBR mode
+                return " -aac_at_mode:a 2" + " -b:a " + bitrate;
             }
 
             if (string.Equals(encoder, "libvorbis", StringComparison.OrdinalIgnoreCase))
@@ -7003,8 +7016,8 @@ namespace MediaBrowser.Controller.MediaEncoding
             var bitrate = state.OutputAudioBitrate;
             if (bitrate.HasValue && !LosslessAudioCodecs.Contains(codec, StringComparison.OrdinalIgnoreCase))
             {
-                var vbrParam = GetAudioVbrModeParam(codec, bitrate.Value / (channels ?? 2));
-                if (encodingOptions.EnableAudioVbr && vbrParam is not null)
+                var vbrParam = GetAudioVbrModeParam(codec, bitrate.Value, channels ?? 2);
+                if (encodingOptions.EnableAudioVbr && state.EnableAudioVbrEncoding && vbrParam is not null)
                 {
                     args += vbrParam;
                 }
@@ -7034,8 +7047,8 @@ namespace MediaBrowser.Controller.MediaEncoding
 
             if (bitrate.HasValue && !LosslessAudioCodecs.Contains(outputCodec, StringComparison.OrdinalIgnoreCase))
             {
-                var vbrParam = GetAudioVbrModeParam(GetAudioEncoder(state), bitrate.Value / (channels ?? 2));
-                if (encodingOptions.EnableAudioVbr && vbrParam is not null)
+                var vbrParam = GetAudioVbrModeParam(GetAudioEncoder(state), bitrate.Value, channels ?? 2);
+                if (encodingOptions.EnableAudioVbr && state.EnableAudioVbrEncoding && vbrParam is not null)
                 {
                     audioTranscodeParams.Add(vbrParam);
                 }