How to play audio from AVAudioPCMBuffer converted from NSData - ios

Question

I am getting audio PCM 16bit Mono data from udp packets like this:
(void)udpSocket:(GCDAsyncUdpSocket *)sock didReceiveData:(NSData *)data
fromAddress:(NSData *)address
withFilterContext:(id)filterContext
{
...
}
I am converting this data into PCM buffer by calling a swift function as below:
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
}
Data is converted to PCM buffer and i can see its length in logs.
But when i try to play the buffer i hear no voice.
Here is the code for receiving:
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

ended up using an objective-c function:data is getting converted fine
-(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;
}