使用AVCapture会话捕获音频帧

Question

我需要捕获音频帧的频率为48000，和Int16位帧。我需要那种格式，因为这正是我的客户所期望的。现在，音频通过，但它听起来真的很有趣。我使用的是avcapture会话和以下设置。

 let audioSettings = [AVFormatIDKey : kAudioFormatLinearPCM,
                    AVSampleRateKey : 48000,
             AVLinearPCMBitDepthKey : 16,
              AVLinearPCMIsFloatKey : false] as [String : Any]

我将这些设置添加到AVCaptureDataOutput对象中

 private func setAudioDataOutput() -> EErrorCode {
    if dataOutput == nil {
        dataOutput = AVCaptureAudioDataOutput()
    }
    dataOutput!.setSampleBufferDelegate(self, queue: DispatchQueue(label: "myApp.AudioStreaming"))
    dataOutput!.audioSettings = audioSettings
    
    guard captureSession!.canAddOutput(dataOutput!) else {
        VsLogger.logError(logTag, "setAudioDataOutput() failed to add dataOutput for \(getName() ?? "no name found")")
        return .AudioOtherError
    }
    captureSession!.addOutput(dataOutput!)
    return .Success
}

这就是我从CMSampleBuffer获得数据的地方。

        guard let bufferData = self.getBlockDataBuffer(from: buffer) else { return }
    delegate.audioDataUpdate(bufferData, Int(sampleDescription.mSampleRate),
                             Int(sampleDescription.mChannelsPerFrame),
                             duration)

我的getBlockDataBuffer功能

   private func getBlockDataBuffer(from sampleBuffer: CMSampleBuffer) -> Data? {
           guard let blockBuffer = CMSampleBufferGetDataBuffer(sampleBuffer) else { return nil }
           let dataLength = CMBlockBufferGetDataLength(blockBuffer)
           var blockBufferData  = [UInt8](repeating: 0, count: dataLength)
           let status = CMBlockBufferCopyDataBytes(blockBuffer, atOffset: 0, dataLength: dataLength,
                                            destination: &blockBufferData)
           guard status == noErr else {
            return nil
           }
           return Data(bytes: blockBufferData , count: dataLength)

当我打印AudioStreamBasicDescription时，我会得到以下内容。

sampleDescription.mChannelsPerFrame -> 2
sampleDescription.mSampleRate -> 48000
sampleDescription.mBytesPerFrame -> 2
sampleDescription.mFramesPerPacket -> 1
sampleDescription.mBytesPerPacket -> 2
duration -> 1

下面是我的cmSampleBuffer的样子：

    buffer numSamples: 557
    buffer duration seconds: 0.011604166666666667
    buffer isValid: true
    buffer totalSampleSize: 0
    buffer numSamples: 557
    buffer dataReadiness: ready
    sampleDescription: AudioStreamBasicDescription(mSampleRate: 48000.0, 
                                         mFormatID: 1819304813,
                                         mFormatFlags: 44,
                                         mBytesPerPacket: 2,
                                         mFramesPerPacket: 1,
                                         mBytesPerFrame: 2,
                                         mChannelsPerFrame: 2,
                                         mBitsPerChannel: 16,
                                         mReserved: 0)

所以我的设置没有在我的捕获会话中持续？

Answer 1

结果(就像@RhythmicFistman建议的那样)，我只是错过了设定的天气，或者不想让这个画面交织在一起。所以我的设置现在是这样的：

    let audioSettings = [AVFormatIDKey : kAudioFormatLinearPCM,
                   AVSampleRateKey : 48000,
            AVLinearPCMBitDepthKey : 16,
             AVLinearPCMIsFloatKey : false,
       AVLinearPCMIsNonInterleaved : false] as [String : Any]