正在处理AVPlayer的音频输出

Question

非常简单的问题：

• 我有一个AVPlayer，正在播放使用UIImagePickerController从我的iphone/ipad库中拍摄的视频
• 我想对视频播放器的音频输出应用各种音频处理，例如滤波器&卷积

最好的方法是什么(即哪个框架/类(？

Answer 1

最好的方法是将音频与视频分离，并使用AVAudioEngine对音频进行音频处理，同时同步两个播放器。

import UIKit
import AVKit
import AVFoundation
extension CGRect {
init(_ x:CGFloat, _ y:CGFloat, _ w:CGFloat, _ h:CGFloat) {
self.init(x:x, y:y, width:w, height:h)}
}
func delay(_ delay:Double, closure:@escaping ()->()) {
let when = DispatchTime.now() + delay
DispatchQueue.main.asyncAfter(deadline: when, execute: closure)
}
class ViewController: UIViewController {
var audioPlayer : AVAudioPlayer!
var engine = AVAudioEngine()
var f = AVAudioFile()
var player = AVAudioPlayerNode()
var effect = AVAudioUnitEQ(numberOfBands: 4)
var timestamp = Date().timeIntervalSince1970
var didInitialLayout = false
var videoplayer = AVPlayer()
var videostate = 0
var freq = [150, 250, 3000, 6000]
override var prefersStatusBarHidden : Bool {
return true
}
override var supportedInterfaceOrientations : UIInterfaceOrientationMask {
if UIDevice.current.userInterfaceIdiom == .pad {
return .all
}
return .landscape
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
try? AVAudioSession.sharedInstance().setCategory(.playback, mode:.default)
try? AVAudioSession.sharedInstance().setActive(true)
}

@IBAction func launchVideoPlayer(_ sender: Any) {
self.videoplayer.pause()
let urlvideo = Bundle.main.url(forResource:"videofile",     withExtension:"mp4")!
self.videoplayer = AVPlayer(url:urlvideo)
let av = AVPlayerViewController()
av.showsPlaybackControls = false
av.player = videoplayer
av.view.frame = CGRect(140,20,1100,800)
self.addChild(av)
self.view.addSubview(av.view)
av.didMove(toParent:self)
self.videostate = 1
}
@IBAction func audioprocess(_ sender: Any) {
self.engine.stop()
self.engine = AVAudioEngine()
self.player = AVAudioPlayerNode()
let url = Bundle.main.url(forResource:"yoursong", withExtension: "m4a")!
self.f = try! AVAudioFile(forReading: url)
self.engine.attach(player)
self.effect = AVAudioUnitEQ(numberOfBands: 4)
let bands = effect.bands
for i in 0...(bands.count - 1) {
bands[i].frequency = Float(self.freq[i])
}
bands[0].gain = 10.0
bands[0].filterType = .parametric
bands[0].bandwidth = 1
bands[1].gain = 10.0
bands[1].filterType = .parametric
bands[1].bandwidth = 0.5
bands[2].gain = 0.0
bands[2].filterType = .parametric
bands[2].bandwidth = 1
bands[3].gain = 0.0
bands[3].filterType = .parametric
bands[3].bandwidth = 1
self.engine.attach(effect)
self.engine.connect(player, to: effect, format: f.processingFormat)
let mixer = self.engine.mainMixerNode
self.engine.connect(effect, to: mixer, format: f.processingFormat)
player.scheduleFile(f, at: nil) {
print("stopping")
delay(0.1) {
if self.engine.isRunning {
print("engine was running, really stopping")
self.engine.stop()
}
}
}
self.engine.prepare()
try! self.engine.start()
player.play()

if self.videostate == 1 {
self.videoplayer.play()
} else {
return }
}
@IBAction func stopsound(_ sender: Any) {
self.player.stop()
self.videoplayer.pause()
}

@IBAction func changeEQ(_ sender: Any) {
let bands = self.effect.bands
for i in 0...(bands.count - 1) {
bands[i].frequency = Float(self.freq[i])
}
bands[0].bypass = false
bands[1].bypass = false
bands[2].bypass = false
bands[3].bypass = false
bands[0].gain = -60.0
bands[0].filterType = .parametric
bands[0].bandwidth = 1
bands[1].gain = -40.0
bands[1].filterType = .parametric
bands[1].bandwidth = 0.5
bands[2].gain = -20.0
bands[2].filterType = .parametric
bands[2].bandwidth = 1
bands[3].gain = 0.0
bands[3].filterType = .parametric
bands[3].bandwidth = 1
self.engine.attach(effect)
}
}