warn on clipping

add option to apply pre-gain
librespot-org · Jan 25, 2018 · 38f18e3 · 38f18e3
1 parent 2eabb93
commit 38f18e3
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Showing 3 changed files with 19 additions and 4 deletions.
diff --git a/core/src/config.rs b/core/src/config.rs
@@ -106,6 +106,7 @@ pub struct PlayerConfig {
     pub onstart: Option<String>,
     pub onstop: Option<String>,
     pub normalization: bool,
+    pub normalization_pre_gain: f32,
 }
 
 impl Default for PlayerConfig {
@@ -115,6 +116,9 @@ impl Default for PlayerConfig {
             onstart: None,
             onstop: None,
             normalization: false,
+            normalization_pre_gain: 0.0, //replaygain target is -14dbfs, may not be enough headroom
+                                         // macOS Spotify client adds 3.0
+                                         // https://community.spotify.com/t5/Social-Off-Topic/How-does-the-loudness-normalization-algorithm-work/td-p/1603671
         }
     }
 }

diff --git a/src/main.rs b/src/main.rs
@@ -101,7 +101,8 @@ fn setup(args: &[String]) -> Setup {
         .optopt("", "backend", "Audio backend to use. Use '?' to list options", "BACKEND")
         .optopt("", "device", "Audio device to use. Use '?' to list options", "DEVICE")
         .optopt("", "mixer", "Mixer to use", "MIXER")
-        .optflag("", "enable-volume-normalization", "Play all tracks at the same volume");
+        .optflag("", "enable-volume-normalization", "Play all tracks at the same volume")
+        .optopt("", "normalization-pre-gain", "Pre-gain (dB) applied by volume normalization", "PREGAIN");
 
     let matches = match opts.parse(&args[1..]) {
         Ok(m) => m,
@@ -170,7 +171,10 @@ fn setup(args: &[String]) -> Setup {
             bitrate: bitrate,
             onstart: matches.opt_str("onstart"),
             onstop: matches.opt_str("onstop"),
-            normalization: matches.opt_present("enable-volume-normalization")
+            normalization: matches.opt_present("enable-volume-normalization"),
+            normalization_pre_gain: matches.opt_str("normalization-pre-gain")
+                .map(|pre_gain| pre_gain.parse::<f32>().expect("Invalid pre-gain float value"))
+                .unwrap_or(PlayerConfig::default().normalization_pre_gain),
         }
     };
 

diff --git a/src/player.rs b/src/player.rs
@@ -221,7 +221,8 @@ impl PlayerInternal {
 
                 if self.config.normalization {
 
-                    let normalization_factor = f32::powf(10.0, track_gain_db / 20.0);
+                    // see http://wiki.hydrogenaud.io/index.php?title=ReplayGain_specification#Loudness_normalization
+                    let normalization_factor = f32::powf(10.0, (track_gain_db + self.config.normalization_pre_gain) / 20.0);
 
                     // info!("Use gain: {}, factor: {}", track_gain_db, normalization_factor);
 
@@ -413,9 +414,15 @@ impl PlayerInternal {
             }
             decrypted_file.seek(SeekFrom::Start(148)).unwrap(); // 4 bytes as LE float
             decrypted_file.read(&mut track_gain_float_bytes).unwrap();
+            let normalization_factor = f32::powf(10.0, (track_gain_db + self.config.normalization_pre_gain) / 20.0);
+            let mut track_peak: f32 = 1.0;
             unsafe {
                 // track peak, 1.0 represents dbfs
-                info!("Track peak: {}", mem::transmute::<[u8; 4], f32>(track_gain_float_bytes));
+                track_peak = mem::transmute::<[u8; 4], f32>(track_gain_float_bytes);
+                info!("Track peak: {}", track_peak);
+                if normalization_factor * track_peak > 1.0 {
+                    warn!("Track will clip, please add negative pre-gain");
+                }
             }
             decrypted_file.seek(SeekFrom::Start(152)).unwrap(); // 4 bytes as LE float
             decrypted_file.read(&mut track_gain_float_bytes).unwrap();