From 7377b4f2ab0549e11d39212ec06519e7be73a00b Mon Sep 17 00:00:00 2001
From: Frank Becker <fb@mooflu.com>
Date: Mon, 22 Feb 2021 12:10:36 -0800
Subject: [PATCH] Add a LinearVolume wrapper for mediaElement.Volume (#834)

Co-authored-by: Frank Becker <frank.becker@thoughtexchange.com>
---
 .../ViewerPanel.xaml                          |  4 +-
 .../ViewerPanel.xaml.cs                       | 39 +++++++++++++++----
 2 files changed, 34 insertions(+), 9 deletions(-)

diff --git a/QuickLook.Plugin/QuickLook.Plugin.VideoViewer/ViewerPanel.xaml b/QuickLook.Plugin/QuickLook.Plugin.VideoViewer/ViewerPanel.xaml
index a50fec1..0943992 100644
--- a/QuickLook.Plugin/QuickLook.Plugin.VideoViewer/ViewerPanel.xaml
+++ b/QuickLook.Plugin/QuickLook.Plugin.VideoViewer/ViewerPanel.xaml
@@ -162,7 +162,7 @@
                     <Button.Style>
                         <Style TargetType="Button" BasedOn="{StaticResource ControlButtonStyle}">
                             <Setter Property="Content"
-                                    Value="{Binding ElementName=mediaElement, Path=Volume, Converter={StaticResource VolumeToIconConverter}}" />
+                                    Value="{Binding ElementName=viewerPanel, Path=LinearVolume, Converter={StaticResource VolumeToIconConverter}}" />
                         </Style>
                     </Button.Style>
                 </Button>
@@ -198,7 +198,7 @@
             <Grid Height="32" Width="130" HorizontalAlignment="Right" VerticalAlignment="Bottom"
                   Background="{DynamicResource CaptionButtonHoverBackground}" Margin="0,0,0,32">
                 <Slider Style="{StaticResource CustomSliderStyle}" Width="110" Maximum="1"
-                        Value="{Binding ElementName=mediaElement, Path=Volume}" />
+                        Value="{Binding ElementName=viewerPanel, Path=LinearVolume}" />
             </Grid>
         </Grid>
     </Grid>
diff --git a/QuickLook.Plugin/QuickLook.Plugin.VideoViewer/ViewerPanel.xaml.cs b/QuickLook.Plugin/QuickLook.Plugin.VideoViewer/ViewerPanel.xaml.cs
index eacf0b1..f26b9cb 100644
--- a/QuickLook.Plugin/QuickLook.Plugin.VideoViewer/ViewerPanel.xaml.cs
+++ b/QuickLook.Plugin/QuickLook.Plugin.VideoViewer/ViewerPanel.xaml.cs
@@ -145,7 +145,7 @@ namespace QuickLook.Plugin.VideoViewer
         public void Dispose()
         {
             // old plugin use an int-typed "Volume" config key ranged from 0 to 100. Let's use a new one here.
-            SettingHelper.Set("VolumeDouble", mediaElement.Volume);
+            SettingHelper.Set("VolumeDouble", LinearVolume);
             SettingHelper.Set("ShouldLoop", ShouldLoop);
 
             try
@@ -280,13 +280,38 @@ namespace QuickLook.Plugin.VideoViewer
                 : Visibility.Visible;
         }
 
+        // Newer .net has Math.Clamp
+        private T Clamp<T>(T val, T min, T max) where T : IComparable<T>
+        {
+            if (val.CompareTo(min) < 0) return min;
+            else if (val.CompareTo(max) > 0) return max;
+            else return val;
+        }
+
+        // A change in amplitude by a factor of 10 corresponds to a 20 dB change
+        private const double DecibelAmplitudeMult = 20.0;
+        public double LinearVolume
+        {
+            // mediaElement.Volume returns [0,1] where 0 = -100db, 1 = 0db
+            // Decibel is logarithmic. See amplitude table https://en.wikipedia.org/wiki/Decibel
+            get
+            {
+                var dbVol = 100.0 * (mediaElement.Volume - 1.0);
+                var linearVol = Math.Pow(10, dbVol / DecibelAmplitudeMult);
+                return linearVol;
+            }
+            set
+            {
+                var linearVol = Clamp(value, 0.00001, 1.0);
+                var dbVol = DecibelAmplitudeMult * Math.Log10(linearVol);
+                mediaElement.Volume = dbVol / 100.0 + 1.0;
+                OnPropertyChanged();
+            }
+        }
+
         private void ChangeVolume(double delta)
         {
-            var newVol = mediaElement.Volume + delta;
-            newVol = Math.Max(newVol, 0);
-            newVol = Math.Min(newVol, 1);
-
-            mediaElement.Volume = newVol;
+            LinearVolume = LinearVolume + delta; // setter will clamp
         }
 
         private void TogglePlayPause(object sender, EventArgs e)
@@ -316,7 +341,7 @@ namespace QuickLook.Plugin.VideoViewer
 
             mediaElement.Source = new Uri(path);
             // old plugin use an int-typed "Volume" config key ranged from 0 to 100. Let's use a new one here.
-            mediaElement.Volume = SettingHelper.Get("VolumeDouble", 1d);
+            LinearVolume = SettingHelper.Get("VolumeDouble", 1d);
 
             mediaElement.Play();
         }