如何检测max dB Swift
我试图在iOS设备上检测dB，但是，我是AV音频基础的新手无法真正弄明白。 我遇到过这个post： iOS – 检测打入麦克风并转换结果！ （迅速） ，但它不适合我。
我目前的代码是这样的：
import Foundation import UIKit import AVFoundation import CoreAudio class ViewController: UIViewController { var recorder: AVAudioRecorder! var levelTimer = NSTimer() var lowPassResults: Double = 0.0 override func viewDidLoad() { super.viewDidLoad() //make an AudioSession, set it to PlayAndRecord and make it active var audioSession:AVAudioSession = AVAudioSession.sharedInstance() audioSession.setCategory(AVAudioSessionCategoryPlayAndRecord, withOptions: nil) audioSession.setActive(true, error: nil) //set up the URL for the audio file var documents: AnyObject = NSSearchPathForDirectoriesInDomains( NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomainMask.UserDomainMask, true)[0] var str = documents.stringByAppendingPathComponent("recordTest.caf") var url = NSURL.fileURLWithPath(str as String) // make a dictionary to hold the recording settings so we can instantiate our AVAudioRecorder var recordSettings: [NSObject : AnyObject] = [AVFormatIDKey:kAudioFormatAppleIMA4, AVSampleRateKey:44100.0, AVNumberOfChannelsKey:2,AVEncoderBitRateKey:12800, AVLinearPCMBitDepthKey:16, AVEncoderAudioQualityKey:AVAudioQuality.Max.rawValue ] //declare a variable to store the returned error if we have a problem instantiating our AVAudioRecorder var error: NSError? //Instantiate an AVAudioRecorder recorder = AVAudioRecorder(URL:url, settings: recordSettings, error: &error) //If there's an error, print otherwise, run prepareToRecord and meteringEnabled to turn on metering (must be run in that order) if let e = error { print(e.localizedDescription) } else { recorder.prepareToRecord() recorder.meteringEnabled = true //start recording recorder.record() //instantiate a timer to be called with whatever frequency we want to grab metering values self.levelTimer = NSTimer.scheduledTimerWithTimeInterval(0.02, target: self, selector: #selector(ViewController.levelTimerCallback), userInfo: nil, repeats: true) } } //This selector/function is called every time our timer (levelTime) fires func levelTimerCallback() { //we have to update meters before we can get the metering values recorder.updateMeters() //print to the console if we are beyond a threshold value. Here I've used -7 if recorder.averagePowerForChannel(0) > -7 { print("Dis be da level I'm hearin' you in dat mic ") print(recorder.averagePowerForChannel(0)) print("Do the thing I want, mofo") } } override func didReceiveMemoryWarning() { super.didReceiveMemoryWarning() // Dispose of any resources that can be recreated. } } 我目前正在构建关于电影制作的应用程序，并学习了如何以dB为单位计量声级。
recorder.averagePowerForChannel的原始数据实际上不是声音的dB级别，它提供的级别范围是-160 – 0 ，所以我们需要一些修改才能使这些数据更合理
所以我发现了一些使这个数据（值）转换为dB级数据的东西。
（抱歉忘记了我被发现的地方！）
这是代码
/** Format dBFS to dB - author: RÅGE_Devil_Jåmeson - date: (2016-07-13) 20:07:03 - parameter dBFSValue: raw value of averagePowerOfChannel - returns: formatted value */ func dBFS_convertTo_dB (dBFSValue: Float) -> Float { var level:Float = 0.0 let peak_bottom:Float = -60.0 // dBFS -> -160..0 so it can be -80 or -60 if dBFSValue < peak_bottom { level = 0.0 } else if dBFSValue >= 0.0 { level = 1.0 } else { let root:Float = 2.0 let minAmp:Float = powf(10.0, 0.05 * peak_bottom) let inverseAmpRange:Float = 1.0 / (1.0 - minAmp) let amp:Float = powf(10.0, 0.05 * dBFSValue) let adjAmp:Float = (amp - minAmp) * inverseAmpRange level = powf(adjAmp, 1.0 / root) } return level }
我注意到你正在录制2个频道，所以它与我的代码差别不大;
希望可以帮助你或给你一些想法：D
最后更新
将编码语言改为快速