Record audio from microphone into .wav format and playback using AudioUnit in Xamarin.ios

See more:

Mono

audio

iOS

Xamarin

I am trying to record audio data from microphone in .wav file and playback it. I need also actual data (amplitude) for ploting graph so i am using AudioUnit. I setup inputCallBack and renderCallBack for AudioUnit object But i don't know how to write AudioBuffers to .wav file from render_CallBack mehtod. I attached my code what i have tried till now.

Please help me...

Step - 1

AudioStreamBasicDescription audioStreamBasicDesc;
AudioUnit.AudioUnit audioUnit;
string m_recordingFilePath;
ExtAudioFile extAudioFileObj;


public override void ViewDidLoad()
            {
                base.ViewDidLoad();


                audioStreamBasicDesc.SampleRate = 16000;
                audioStreamBasicDesc.Format = AudioFormatType.LinearPCM;
                audioStreamBasicDesc.FramesPerPacket = 1;
                audioStreamBasicDesc.ChannelsPerFrame = 1;
                audioStreamBasicDesc.BytesPerFrame = audioStreamBasicDesc.ChannelsPerFrame * sizeof(short);
                audioStreamBasicDesc.BytesPerPacket = audioStreamBasicDesc.ChannelsPerFrame * sizeof(short);
                audioStreamBasicDesc.BitsPerChannel = 16;
                audioStreamBasicDesc.Reserved = 0;
                audioStreamBasicDesc.FormatFlags = AudioFormatFlags.IsSignedInteger | AudioFormatFlags.IsPacked;

var documents = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);
            var tmp = Path.Combine(documents, "..", "tmp");
            m_recordingFilePath = Path.Combine(tmp, String.Format("{0}.wav", "MyFile" + DateTime.Now.ToString("MM-dd-yyyy HH-mm-ss", CultureInfo.InvariantCulture)));       
extAudioFileObj = ExtAudioFile.CreateWithUrl(CFUrl.FromFile(m_recordingFilePath), AudioFileType.WAVE, audioStreamBasicDesc, AudioFileFlags.EraseFlags);
                prepareAudioUnit();
       }

Step - 2

public void prepareAudioUnit()
        {

            var _audioComponent =   AudioComponent.FindComponent(AudioTypeOutput.Remote);

            audioUnit = _audioComponent.CreateAudioUnit();

            audioUnit = new AudioUnit.AudioUnit(_audioComponent);

            audioUnit.SetEnableIO(true,
                AudioUnitScopeType.Input,
                1 // Remote Input
            );

            // setting audio format
            audioUnit.SetAudioFormat(audioStreamBasicDesc,
                AudioUnitScopeType.Output,
                1
            );                                    

            audioUnit.SetInputCallback(input_CallBack, AudioUnitScopeType.Input, 1);

            audioUnit.SetRenderCallback(render_CallBack, AudioUnitScopeType.Global, 0);


            audioUnit.Initialize();
            audioUnit.Start();
        }

Step - 3

AudioUnitStatus input_CallBack(AudioUnitRenderActionFlags actionFlags, AudioTimeStamp timeStamp, uint busNumber, uint numberFrames, AudioUnit.AudioUnit audioUnit)
        {
            return AudioUnitStatus.NoError;
        }

Step - 4

AudioUnitStatus render_CallBack(AudioUnitRenderActionFlags actionFlags, AudioTimeStamp timeStamp, uint busNumber, uint numberFrames, AudioBuffers data)
        {
            // getting microphone input signal
            var status = audioUnit.Render(ref actionFlags,
                             timeStamp,
                             1, // Remote input
                             numberFrames,
                             data);
            if (status != AudioUnitStatus.OK)
            {
                return status;
            }

            //get pointer to buffer
            var outP = data[0].Data;
            unsafe
            {
                var outPtr = (int*)outP.ToPointer();
                for (int i = 0; i < numberFrames; i++)
                {
                    var val = *outPtr;
                    outPtr++;
                    //lastestPickVal = val; //This is for ploting graph
                    Console.WriteLine(val);
                }
            }
        extAudioFileObj.ClientDataFormat = audioStreamBasicDesc;
        var err = extAudioFileObj.Write(numberFrames, data); //Here i am trying to write data into .wav file and file is generated also but corrupted file without actual data (create file size is approx 4kb or 100 kb )
            Console.WriteLine("OUTPUT" + busNumber);
            return AudioUnitStatus.NoError;
        }