Multi tool use

Xamarin.Android and RecordAudio: how to combine file writing and other task

I develop a Xamarin.Android app where I need to record an audio file in a .wav and to display the related spectrogram in the same time.

I'm able to perform the 2 tasks separately but not to combine them.

I use an AudioRecord to record the sound through the microphone:

AudioRecord

public async Task StartRecording()
{
audioRecord = new AudioRecord(AudioSource.Mic, 44100, ChannelIn.Mono, Android.Media.Encoding.Pcm16bit, bufferSize);
if (audioRecord.State == State.Initialized)
audioRecord.StartRecording();
isRecording = true;
recordingThread = new System.Threading.Thread(new ThreadStart(
WriteAudioDataToFile
));
recordingThread.Start();
}


The file writing is done in WriteAudioDataToFile() and works fine:

WriteAudioDataToFile()

private void WriteAudioDataToFile()
{
byte data = new byte[bufferSize];
string filename = GetTempFilename();
FileOutputStream fos = null;
try
{
fos = new FileOutputStream(filename);
}
catch (Java.IO.FileNotFoundException e)
{
}
int read = 0;

if (null != fos)
{
while (isRecording)
{
read = audioRecord.Read(data, 0, bufferSize);
if ((int)RecordStatus.ErrorInvalidOperation != read)
{
try
{
fos.Write(data);
}
catch (Java.IO.IOException e)
{
}
}
}
try
{
fos.Close();
}
catch (Java.IO.IOException e)
{
}
}
}


I would like to do the other task after the file is written:

void OnNext()
{
short audioBuffer = new short[2048];
audioRecord.Read(audioBuffer, 0, audioBuffer.Length);
int result = new int[audioBuffer.Length];
for (int i = 0; i < audioBuffer.Length; i++)
{
result[i] = (int)audioBuffer[i];
}
samplesUpdated(this, new SamplesUpdatedEventArgs(result));
}


If I call OnNext() from StartRecording(), without writing the file this works fine and I get the expected values for the spectrogram:

OnNext()

StartRecording()

public async Task StartRecording()
{
audioRecord = new AudioRecord(AudioSource.Mic, 44100, ChannelIn.Mono, Android.Media.Encoding.Pcm16bit, bufferSize);
if (audioRecord.State == State.Initialized)
audioRecord.StartRecording();
isRecording = true;
while (audioRecord.RecordingState == RecordState.Recording)
{
OnNext();
}
}


But as I need to combine both file writing and other task, I tried to move the OnNext() method after the file writing:

OnNext()

private void WriteAudioDataToFile()
{
//...
try
{
fos.Write(data);

short dataShort = new short[bufferSize];
dataShort = Array.ConvertAll(data, d => (short)d);
int result = new int[dataShort.Length];
for (int i = 0; i < dataShort.Length; i++)
{
result[i] = (int)dataShort[i];
}
samplesUpdated(this, new SamplesUpdatedEventArgs(result));
}
catch (Java.IO.IOException e)
{
}
//...
}


But this doesn't work at all as expected:

byte

short

I don't see how to manage audioRecord.Read(data, 0, bufferSize):

audioRecord.Read(data, 0, bufferSize)

byte

fos.Write(data);

short

=> What should be the better approach to achieve this?

Edit:

I've already tried these approaches but this didn't change anything:

I've also looked if it is possible to wirte the file after the AudioRecord has stopped, but it doesn't seem possible too...

This question has not received enough attention.

I've passed some time to tests alternatvies: - parallel threads working on the same AudioRecord - parallel threads working on 2 distincts AudioRecords But this didn't work as expected.

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