ios - 从 CMSampleBuffer 播放音频

Question

我在 iOS 中为群组创建了一个视频聊天应用程序。我一直在寻找一些方法来分别控制不同参与者的音量。我找到了使用 RemoteAudioTrack 中的 isPlaybackEnabled 静音和取消静音的方法，但无法控制音量。

我也想过我们是否可以在AVAudioPlayer中使用它。我找到了 addSink。这是我从 here 中尝试过的:

class Audio: NSObject, AudioSink {
    var a = 1
    func renderSample(_ audioSample: CMSampleBuffer!) {
        print("audio found", a)
        a += 1

        var audioBufferList = AudioBufferList()
        var data = Data()
        var blockBuffer : CMBlockBuffer?

        CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(audioSample, bufferListSizeNeededOut: nil, bufferListOut: &audioBufferList, bufferListSize: MemoryLayout<AudioBufferList>.size, blockBufferAllocator: nil, blockBufferMemoryAllocator: nil, flags: 0, blockBufferOut: &blockBuffer)
        let buffers = UnsafeBufferPointer<AudioBuffer>(start: &audioBufferList.mBuffers, count: Int(audioBufferList.mNumberBuffers))

        for audioBuffer in buffers {
            let frame = audioBuffer.mData?.assumingMemoryBound(to: UInt8.self)
            data.append(frame!, count: Int(audioBuffer.mDataByteSize))
        }

        let player = try! AVAudioPlayer(data: data) //crash here
        player.play()
    }
}

但它在 let player = try! 时崩溃了! AVAudioPlayer(数据:数据)。

编辑:
这是错误: fatal error :“尝试!”表达式意外引发错误:Error Domain=NSOSStatusErrorDomain Code=-39 "(null)": file。

这是数据，所以我猜它没有被转换:

▿ 0 bytes
  - count : 0
  ▿ pointer : 0x000000016d7ae160
    - pointerValue : 6131736928
  - bytes : 0 elements

这是audioSample:

<CMAudioFormatDescription 0x2815a3de0 [0x1bb2ef830]> {
    mediaType:'soun' 
    mediaSubType:'lpcm' 
    mediaSpecific: {
        ASBD: {
            mSampleRate: 16000.000000 
            mFormatID: 'lpcm' 
            mFormatFlags: 0xc 
            mBytesPerPacket: 2 
            mFramesPerPacket: 1 
            mBytesPerFrame: 2 
            mChannelsPerFrame: 1 
            mBitsPerChannel: 16     } 
        cookie: {(null)} 
        ACL: {(null)}
        FormatList Array: {(null)} 
    } 
    extensions: {(null)}
}

Answer 1

您可以从CMSampleBuffer 获取完整的数据缓冲区并将其转换为Data:

let blockBuffer = CMSampleBufferGetDataBuffer(sampleBuffer)
let blockBufferDataLength = CMBlockBufferGetDataLength(blockBuffer!)
var blockBufferData  = [UInt8](repeating: 0, count: blockBufferDataLength)
let status = CMBlockBufferCopyDataBytes(blockBuffer!, atOffset: 0, dataLength: blockBufferDataLength, destination: &blockBufferData)
guard status == noErr else { return }
let data = Data(bytes: blockBufferData, count: blockBufferDataLength)

同时引用 AVAudioPlayer概述:

Use this class for audio playback unless you are playing audio captured from a network stream or require very low I/O latency.

所以我认为它不适合你。你最好使用 AVAudioEngine或 Audio Queue Services .