Better envelope curve control (#92)

README.md

@@ -26,4 +26,4 @@ what is supported, please visit the `SampleSoundfont` documentation in `core`.
 
 ## License
 
-XSynth is licensed under the GNU Lesser General Public License 3.0.
+XSynth is licensed under the MIT license.

core/examples/core_samples_per_second.rs

@@ -2,7 +2,10 @@ use std::{sync::Arc, time::Instant};
 
 use xsynth_core::{
     channel::{ChannelAudioEvent, ChannelConfigEvent, ChannelEvent, VoiceChannel},
-    soundfont::{Interpolator, SampleSoundfont, SoundfontBase, SoundfontInitOptions},
+    soundfont::{
+        EnvelopeCurveType, EnvelopeOptions, Interpolator, SampleSoundfont, SoundfontBase,
+        SoundfontInitOptions,
+    },
     AudioPipe, AudioStreamParams, ChannelCount,
 };
 
@@ -33,8 +36,12 @@ pub fn main() {
             SoundfontInitOptions {
                 bank: None,
                 preset: None,
+                vol_envelope_options: EnvelopeOptions {
+                    attack_curve: EnvelopeCurveType::Exponential,
+                    decay_curve: EnvelopeCurveType::Exponential,
+                    release_curve: EnvelopeCurveType::Exponential,
+                },
                 interpolator: Interpolator::Nearest,
-                linear_release: false,
                 use_effects: false,
             },
         )

core/src/soundfont/config.rs

@@ -13,6 +13,53 @@ pub enum Interpolator {
     Linear,
 }
 
+/// Type of curve to be used in certain envelope stages.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+pub enum EnvelopeCurveType {
+    /// Apply a linear curve to the envelope stage.
+    /// This option is supported by the attack, decay and release stages.
+    Linear,
+
+    /// Apply an exponential curve to the envelope stage.
+    /// The decay and release stages will use a concave curve, while the
+    /// attack stage will use a convex curve.
+    Exponential,
+}
+
+/// Options for the curves of a specific envelope.
+#[derive(Clone, Copy, Debug, PartialEq)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+pub struct EnvelopeOptions {
+    /// Controls the type of curve of the attack envelope stage. See the
+    /// documentation of the `EnvelopeCurveType` enum for available options.
+    ///
+    /// Default: `Convex`
+    pub attack_curve: EnvelopeCurveType,
+
+    /// Controls the type of curve of the decay envelope stage. See the
+    /// documentation of the `EnvelopeCurveType` enum for available options.
+    ///
+    /// Default: `Linear`
+    pub decay_curve: EnvelopeCurveType,
+
+    /// Controls the type of curve of the release envelope stage. See the
+    /// documentation of the `EnvelopeCurveType` enum for available options.
+    ///
+    /// Default: `Linear`
+    pub release_curve: EnvelopeCurveType,
+}
+
+impl Default for EnvelopeOptions {
+    fn default() -> Self {
+        Self {
+            attack_curve: EnvelopeCurveType::Exponential,
+            decay_curve: EnvelopeCurveType::Linear,
+            release_curve: EnvelopeCurveType::Linear,
+        }
+    }
+}
+
 /// Options for initializing/loading a new sample soundfont.
 #[derive(Clone, Copy, Debug, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
@@ -29,11 +76,9 @@ pub struct SoundfontInitOptions {
     /// Default: `None`
     pub preset: Option<u8>,
 
-    /// If set to true, the voices generated using this soundfont will
-    /// release using a linear function instead of convex.
-    ///
-    /// Default: `false`
-    pub linear_release: bool,
+    /// Configures the volume envelope curves in the dB scale. See the
+    /// documentation for `EnvelopeOptions` for more information.
+    pub vol_envelope_options: EnvelopeOptions,
 
     /// If set to true, the voices generated using this soundfont will
     /// be able to use signal processing effects. Currently this option
@@ -54,7 +99,7 @@ impl Default for SoundfontInitOptions {
         Self {
             bank: None,
             preset: None,
-            linear_release: false,
+            vol_envelope_options: Default::default(),
             use_effects: true,
             interpolator: Interpolator::Nearest,
         }

core/src/soundfont/mod.rs

@@ -29,7 +29,7 @@ mod voice_spawners;
 use utils::*;
 use voice_spawners::*;
 
-pub use config::{Interpolator, SoundfontInitOptions};
+pub use config::*;
 
 pub trait VoiceSpawner: Sync + Send {
     fn spawn_voice(&self, control: &VoiceControlData) -> Box<dyn Voice>;
@@ -244,9 +244,10 @@ impl SampleSoundfont {
             if !exists {
                 unique_envelope_params.push((
                     envelope_descriptor,
-                    Arc::new(
-                        envelope_descriptor.to_envelope_params(stream_params.sample_rate, options),
-                    ),
+                    Arc::new(envelope_descriptor.to_envelope_params(
+                        stream_params.sample_rate,
+                        options.vol_envelope_options,
+                    )),
                 ));
             }
         }
@@ -397,7 +398,10 @@ impl SampleSoundfont {
             for region in preset.regions {
                 let envelope_params = Arc::new(
                     envelope_descriptor_from_region_params(&region.ampeg_envelope)
-                        .to_envelope_params(stream_params.sample_rate, options),
+                        .to_envelope_params(
+                            stream_params.sample_rate,
+                            options.vol_envelope_options,
+                        ),
                 );
 
                 for key in region.keyrange.clone() {