From df76bcca6c5b7220c806a733a24bea4cfa8ec538 Mon Sep 17 00:00:00 2001
From: shogo4405 <shogo4405@gmail.com>
Date: Thu, 25 Apr 2024 20:20:09 +0900
Subject: [PATCH] Add volume control feature by track.

---
 .../AVAudioPCMBuffer+Extension.swift          | 38 ++++++++++++++++++-
 Sources/IO/IOAudioMixerTrack.swift            | 19 +++-------
 2 files changed, 43 insertions(+), 14 deletions(-)

diff --git a/Sources/Extension/AVAudioPCMBuffer+Extension.swift b/Sources/Extension/AVAudioPCMBuffer+Extension.swift
index b24e7cf4c..67f839fa4 100644
--- a/Sources/Extension/AVAudioPCMBuffer+Extension.swift
+++ b/Sources/Extension/AVAudioPCMBuffer+Extension.swift
@@ -1,3 +1,4 @@
+import Accelerate
 import AVFoundation
 
 extension AVAudioPCMBuffer {
@@ -34,7 +35,7 @@ extension AVAudioPCMBuffer {
     }
 
     @discardableResult
-    @inline(__always)
+    @inlinable
     final func copy(_ audioBuffer: AVAudioBuffer) -> Bool {
         guard let audioBuffer = audioBuffer as? AVAudioPCMBuffer, frameLength == audioBuffer.frameLength else {
             return false
@@ -70,6 +71,7 @@ extension AVAudioPCMBuffer {
     }
 
     @discardableResult
+    @inlinable
     final func muted(_ isMuted: Bool) -> AVAudioPCMBuffer {
         guard isMuted else {
             return self
@@ -103,4 +105,38 @@ extension AVAudioPCMBuffer {
         }
         return self
     }
+
+    @inlinable
+    final func volume(_ value: Float) -> Self {
+        guard value < 1.0 && format.commonFormat == .pcmFormatFloat32 else {
+            return self
+        }
+        var count = value
+        if format.isInterleaved {
+            if let floatChannelData = floatChannelData?[0] {
+                vDSP_vsmul(
+                    floatChannelData,
+                    1,
+                    &count,
+                    floatChannelData,
+                    1,
+                    UInt(frameLength * format.channelCount)
+                )
+            }
+        } else {
+            for i in 0..<Int(format.channelCount) {
+                if let floatChannelData = floatChannelData?[i] {
+                    vDSP_vsmul(
+                        floatChannelData,
+                        1,
+                        &count,
+                        floatChannelData,
+                        1,
+                        UInt(frameLength)
+                    )
+                }
+            }
+        }
+        return self
+    }
 }
diff --git a/Sources/IO/IOAudioMixerTrack.swift b/Sources/IO/IOAudioMixerTrack.swift
index 86d49cc87..bc6a677e2 100644
--- a/Sources/IO/IOAudioMixerTrack.swift
+++ b/Sources/IO/IOAudioMixerTrack.swift
@@ -11,11 +11,14 @@ protocol IOAudioMixerTrackDelegate: AnyObject {
 
 /// Constraints on the audio mixier track's settings.
 public struct IOAudioMixerTrackSettings: Codable {
+    /// Specifies the volume for output. 
+    public var volume: Float = 1.0
+
     /// Specifies the muted that indicates whether the audio output is muted.
-    public var isMuted: Bool
+    public var isMuted = false
 
     /// Specifies the mixes the channels or not. Currently, it supports input sources with 4, 5, 6, and 8 channels.
-    public var downmix: Bool
+    public var downmix = true
 
     /// Specifies the map of the output to input channels.
     /// ## Example code:
@@ -25,16 +28,6 @@ public struct IOAudioMixerTrackSettings: Codable {
     /// ```
     public var channelMap: [Int]?
 
-    /// Creates a new instance of a settings.
-    public init(
-        isMuted: Bool = false,
-        downmix: Bool = true,
-        channelMap: [Int]? = nil) {
-        self.isMuted = isMuted
-        self.downmix = downmix
-        self.channelMap = channelMap
-    }
-
     func apply(_ converter: AVAudioConverter?, oldValue: IOAudioMixerTrackSettings?) {
         guard let converter else {
             return
@@ -205,7 +198,7 @@ final class IOAudioMixerTrack<T: IOAudioMixerTrackDelegate> {
             case .haveData:
                 let time = AVAudioTime(sampleTime: sampleTime, atRate: outputBuffer.format.sampleRate)
                 if let anchor, let when = time.extrapolateTime(fromAnchor: anchor) {
-                    delegate?.track(self, didOutput: outputBuffer.muted(settings.isMuted), when: when)
+                    delegate?.track(self, didOutput: outputBuffer.volume(settings.volume).muted(settings.isMuted), when: when)
                 }
                 sampleTime += 1024
             case .error: