如何播放從NSData轉換而來的AVAudioPCMBuffer的音頻

Question

我從udp數據包獲取音頻PCM 16位Mono數據，如下所示：

(void)udpSocket:(GCDAsyncUdpSocket *)sock didReceiveData:(NSData *)data
                                               fromAddress:(NSData *)address
                                         withFilterContext:(id)filterContext
{
...
}

我通過調用swift函數將此數據轉換為PCM緩沖區，如下所示：

func toPCMBuffer(data: NSData) -> AVAudioPCMBuffer {
    let audioFormat = AVAudioFormat(commonFormat: AVAudioCommonFormat.PCMFormatFloat32, sampleRate: 8000, channels: 1, interleaved: false)  // given NSData audio format
    var PCMBuffer = AVAudioPCMBuffer(PCMFormat: audioFormat, frameCapacity:1024*10)
    PCMBuffer.frameLength = PCMBuffer.frameCapacity

    let channels = UnsafeBufferPointer(start: PCMBuffer.floatChannelData, count: Int(PCMBuffer.format.channelCount))

    data.getBytes(UnsafeMutablePointer<Void>(channels[0]) , length: data.length)

    return PCMBuffer
}

數據被轉換為PCM緩沖區，我可以在日志中看到它的長度。 但是當我嘗試播放緩沖區時，我聽不到任何聲音。 這是接收的代碼：

func toPCMBuffer(data: NSData) -> AVAudioPCMBuffer {
        let audioFormat = AVAudioFormat(commonFormat: AVAudioCommonFormat.PCMFormatFloat32, sampleRate: 8000, channels: 1, interleaved: false)  // given NSData audio format
        var PCMBuffer = AVAudioPCMBuffer(PCMFormat: audioFormat, frameCapacity:1024*10)
        PCMBuffer.frameLength = PCMBuffer.frameCapacity

        let channels = UnsafeBufferPointer(start: PCMBuffer.floatChannelData, count: Int(PCMBuffer.format.channelCount))

        data.getBytes(UnsafeMutablePointer<Void>(channels[0]) , length: data.length)
        var mainMixer = audioEngine.mainMixerNode
        audioEngine.attachNode(audioFilePlayer)
        audioEngine.connect(audioFilePlayer, to:mainMixer, format: PCMBuffer.format)
        audioEngine.startAndReturnError(nil)

        audioFilePlayer.play()
        audioFilePlayer.scheduleBuffer(PCMBuffer, atTime: nil, options: nil, completionHandler: nil)
        return PCMBuffer
    }

Answer 1

最終使用了一個objective-c函數：數據轉換得很好

-(AudioBufferList *) getBufferListFromData: (NSData *) data
{
    if (data.length > 0)
    {
        NSUInteger len = [data length];
        //NSData *d2 = [data subdataWithRange:NSMakeRange(4, 1028)];
        //I guess you can use Byte*, void* or Float32*. I am not sure if that makes any difference.
        Byte* byteData = (Byte*) malloc (len);
        memcpy (byteData, [data bytes], len);
        if (byteData)
        {
            AudioBufferList * theDataBuffer =(AudioBufferList*)malloc(sizeof(AudioBufferList) * 1);
            theDataBuffer->mNumberBuffers = 1;
            theDataBuffer->mBuffers[0].mDataByteSize =(UInt32) len;
            theDataBuffer->mBuffers[0].mNumberChannels = 1;
            theDataBuffer->mBuffers[0].mData = byteData;
            // Read the data into an AudioBufferList
            return theDataBuffer;
        }
    }
    return nil;
}