Question

使用AVAudioPlayer后，currentPosition用于获取＆amp;设置位置，但在AVAudioEngine＆amp;使用AVAudioPlayerNode？

Answer 1

AVAudioEngine比AVAudioPlayer更复杂。因此，要查找当前位置，必须使用sampleTime / sampleRate。 sampleTime位于AVAudioPlayerNode的lastRenderTime中，sampleRate位于AVAudioFile的fileFormat中。

此外，如果您想设置currentPosition，则需要使用AVAudioPCMBuffer将数据流式传输到播放器中。然后使用设置AVAudioFile的framePosition属性来向前移动文件指针。你必须将它与AVAudioPlayerNode的playAtTime：函数结合使用来设置玩家的当前时间。

编辑：由于从GitHub中删除了链接

Answer 2

考虑到这个主题的用处，我想分享我的答案。

与AVAudioEngine一起使用的播放器是AVAudioPlayerNode。

您需要什么：

@property (weak,nonatomic) AVAudioPlayerNode *player;
@property (weak,nonatomic) AVAudioFile *file;
AVAudioFramePosition songLengthSamples;
float sampleRateSong;
float lengthSongSeconds;
float startInSongSeconds;

开始播放文件后

lengthSongSamples = self.file.length;
AVAudioFormat *songFormat = self.file.processingFormat;
sampleRateSong=songFormat.sampleRate;
lengthSongSeconds=lengthSongSamples/sampleRateSong;

在阅读文件时获取AVAudioPlayerNode的播放位置：

if(self.player.isPlaying){
    AVAudioTime *nodeTime=self.player.lastRenderTime;
    AVAudioTime *playerTime=[self.player playerTimeForNodeTime:nodeTime];
    float elapsedSeconds=startInSongSeconds+((double)playerTime.sampleTime/sampleRateSong);
    NSLog(@"Elapsed seconds: %f",elapsedSeconds);    
}

在阅读文件时设置AVAudioPlayerNode的播放位置：

[self.player stop];
startInSongSeconds=12.5; // example
unsigned long int startSample = (long int)floor(startInSongSeconds*sampleRateSong);
unsigned long int lengthSamples = songLengthSamples-startSample;

[self.player scheduleSegment:self.file startingFrame:startSample frameCount:(AVAudioFrameCount)lengthSamples atTime:nil completionHandler:^{
    // do something (pause player)
}];
[self.player play];

Answer 3

如果有人急需这个，我将danyadd的答案转换为Swift 3并制作了一个简单的玩家类。

class EasyPlayer {
    var engine: AVAudioEngine!
    var player: AVAudioPlayerNode!
    var audioFile : AVAudioFile!
    var songLengthSamples: AVAudioFramePosition!

    var sampleRateSong: Float = 0
    var lengthSongSeconds: Float = 0
    var startInSongSeconds: Float = 0

    let pitch : AVAudioUnitTimePitch

    init() {
        engine = AVAudioEngine()
        player = AVAudioPlayerNode()
        player.volume = 1.0

        let path = Bundle.main.path(forResource: "filename", ofType: "mp3")!
        let url = NSURL.fileURL(withPath: path)

        audioFile = try? AVAudioFile(forReading: url)
        songLengthSamples = audioFile.length

        let songFormat = audioFile.processingFormat
        sampleRateSong = Float(songFormat.sampleRate)
        lengthSongSeconds = Float(songLengthSamples) / sampleRateSong

        let buffer = AVAudioPCMBuffer(pcmFormat: audioFile!.processingFormat, frameCapacity: AVAudioFrameCount(audioFile!.length))
        do {
            try audioFile!.read(into: buffer)
        } catch _ {
        }

        pitch = AVAudioUnitTimePitch()
        pitch.pitch = 1
        pitch.rate = 1

        engine.attach(player)
        engine.attach(pitch)
        engine.connect(player, to: pitch, format: buffer.format)
        engine.connect(pitch, to: engine.mainMixerNode, format: buffer.format)
        player.scheduleBuffer(buffer, at: nil, options: AVAudioPlayerNodeBufferOptions.loops, completionHandler: nil)
        engine.prepare()

        do {
            try engine.start()
        } catch _ {
        }
    }

    func setPitch(_ pitch: Float) {
        self.pitch.pitch = pitch
    }

    func play() {
        player.play()
    }

    func pause() {
        player.pause()
    }

    func getCurrentPosition() -> Float {
        if(self.player.isPlaying){
            if let nodeTime = self.player.lastRenderTime, let playerTime = player.playerTime(forNodeTime: nodeTime) {
                let elapsedSeconds = startInSongSeconds + (Float(playerTime.sampleTime) / Float(sampleRateSong))
                print("Elapsed seconds: \(elapsedSeconds)")
                return elapsedSeconds
            }
        }
        return 0
    }

    func seekTo(time: Float) {
        player.stop()

        let startSample = floor(time * sampleRateSong)
        let lengthSamples = Float(songLengthSamples) - startSample

        player.scheduleSegment(audioFile, startingFrame: AVAudioFramePosition(startSample), frameCount: AVAudioFrameCount(lengthSamples), at: nil, completionHandler: {self.player.pause()})
        player.play()
    }
}

获取和设置播放位置AVAudioEngine

3 个答案: