PCM stream/Microphone stutter
android, android-asynctask, audiorecord, pcm
Solution
After hours and hours of desperately searching for a solution I have finally found the error.
I accidentaly created my short buffer in the Microphone class like this:
mBuffer = new short[mBufferSize];
The buffer size is in bytes though, so I of course have to use mBuffersize/2
mBuffer = new short[mBufferSize/2];
I will keep my question online in case anyone is interested in the code and /or has a similar problem.
Problem
I am currently developing an Android application that has to record the microphone input as PCM stream. Whenever I record something, I experience some strange stutter and I can't find a solution to this. Here's my code: In my MainActivity I have an ASyncTask for the Microphone input: ``` ArrayList<byte[]> mBufferList; @Override protected String doInBackground(String... params) { Thread.currentThread().setPriority(Thread.MAX_PRIORITY); mMicrophone = new Microphone(); mMicrophone.init(); byte[] buffer; while (mRecord) { try { mMicrophone.record(); buffer = mMicrophone.getBuffer(); mBufferList.add(buffer); } catch { } } } ``` In my Microphone class I initialize the AudioRecorder: ``` public void init() { Log.d("DEBUG", "Microphone: Recording started"); mBufferSize = AudioRecord.getMinBufferSize(44100, AudioFormat.CHANNEL_IN_STEREO, AudioFormat.ENCODING_PCM_16BIT); mRecorder = new AudioRecord(AudioSource.MIC, 44100, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT, mBufferSize); mRecorder.startRecording(); mBuffer = new short[mBufferSize]; } ``` The record method: ``` public void record() throws IOException { mRecorder.read(mBuffer, 0, mBufferSize); } ``` Short[] to Byte[]: ``` public byte[] shortToBytes(short[] sData) { int shortArrsize = sData.length; byte[] bytes = new byte[shortArrsize * 2]; for (int i = 0; i < shortArrsize; i++) { bytes[i * 2] = (byte) (sData[i] & 0x00FF); bytes[(i * 2) + 1] = (byte) (sData[i] >> 8); sData[i] = 0; } return bytes; } ``` Method to retrieve the buffer: ``` public byte[] getBuffer() { byte[] buffer = shortToBytes(mBuffer); return buffer; } ``` I have uploaded a wav-file which demonstrates the stutter effect. I'm saying 'One': Wav-File I already tried to change the samplerates, buffersizes et cetera, but with no avail. Any help is very appreciated! Would be great if anyone could help me out! Please note: This error is not caused by the way I replay the pcm stream since I have tested it on an android devices and even sent the raw data to a server to convert the file to a wav there.