Question

我已经找到了使用AVAudioEngine＆amp; amp;成功输出sampleRate 22050 aac格式audioFile。

在我查看代码之后，有一个问题是我必须使用setCategory AVAudioSessionCategoryPlayAndRecord而不是AVAudioSessionCategoryRecord。

如何改进使用“AVAudioSessionCategoryRecord”的代码 “PlayAndRecord”？

（在这种情况下我应该使用“AVAudioSessionCategoryRecord”，对吧？）

如果我将setCategory设置为AVAudioSessionCategoryRecord，我会收到错误：

AVAudioEngineGraph.mm:1070：初始化：必需条件为false：   IsFormatSampleRateAndChannelCountValid（outputHWFormat）

由于未捕获的异常而终止应用   'com.apple.coreaudio.avfaudio'，原因：'所需条件为假：   IsFormatSampleRateAndChannelCountValid（outputHWFormat）'

有一个关于在AVAudioSessionCategoryRecord中使用麦克风的例子，在我看来，我们只能用inputNode进行记录。 https://developer.apple.com/library/prerelease/content/samplecode/SpeakToMe/Introduction/Intro.html

以下代码现在可以正常工作。

import UIKit
import AVFoundation

class ViewController: UIViewController {

    let audioEngine = AVAudioEngine()
    lazy var inputNode : AVAudioInputNode = {
        return self.audioEngine.inputNode!
    }()

    let sampleRate = Double(22050)
    lazy var outputFormat : AVAudioFormat = {
        return AVAudioFormat(commonFormat: self.inputNode.outputFormatForBus(0).commonFormat,
                             sampleRate: self.sampleRate,
                             channels: AVAudioChannelCount(1),
                             interleaved: false)
    }()

    let converterNode = AVAudioMixerNode()
    lazy var aacFileURL : NSURL = {
        let dirPath = NSURL(fileURLWithPath: NSTemporaryDirectory(), isDirectory: true)
        let filePath = dirPath.URLByAppendingPathComponent("rec.aac")
        return filePath
    }()

    lazy var outputAACFile : AVAudioFile = {
        var settings = self.outputFormat.settings
        settings[AVFormatIDKey] = NSNumber(unsignedInt: kAudioFormatMPEG4AAC)
        return try! AVAudioFile(forWriting: self.aacFileURL,
                                settings:settings)
    }()

    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)

        let audioSession = AVAudioSession.sharedInstance()
        try! audioSession.setCategory(AVAudioSessionCategoryPlayAndRecord)
        try! audioSession.setActive(true)

        self.audioEngine.attachNode(converterNode)
        self.audioEngine.connect(inputNode,
                                 to: converterNode,
                                 format: inputNode.outputFormatForBus(0))

        self.audioEngine.connect(converterNode,
                                 to: self.audioEngine.mainMixerNode,
                                 format: outputFormat)

        converterNode.volume = 0

        converterNode.installTapOnBus(0, bufferSize: 1024, format: converterNode.outputFormatForBus(0)) { (buffer, when) in

            try! self.outputAACFile.writeFromBuffer(buffer)
        }

        try! self.audioEngine.start()
    }
}

使用AVAudioEngine，AVAudioSession setCategory AVAudioSessionCategoryRecord记录和重新采样到aac格式？

1 个答案: