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POPlaying back sound coming from microphone in real-time
 

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    <p>I've been trying to get my application recording the sound coming from the microphone and playing it back in (approximately) real-time, however without success.</p> <p>I'm using AudioRecord and AudioTrack classes for record and playback, respectively. I've tried different approaches, I've tried to record the incoming sound and write it to a file and it worked fine. I've also tried to playback sound from that file AFTER with AudioTrack and it worked fine too. The problem is when I try to play the sound in real-time, instead of reading a file after it's written.</p> <p>Here is the code:</p> <pre><code>//variables private int audioSource = MediaRecorder.AudioSource.MIC; private int samplingRate = 44100; /* in Hz*/ private int channelConfig = AudioFormat.CHANNEL_CONFIGURATION_MONO; private int audioFormat = AudioFormat.ENCODING_PCM_16BIT; private int bufferSize = AudioRecord.getMinBufferSize(samplingRate, channelConfig, audioFormat); private int sampleNumBits = 16; private int numChannels = 1; // … AudioRecord recorder = new AudioRecord(audioSource, samplingRate, channelConfig, audioFormat, bufferSize); recorder.startRecording(); isRecording = true; AudioTrack audioPlayer = new AudioTrack(AudioManager.STREAM_MUSIC, 44100, AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT, bufferSize, AudioTrack.MODE_STREAM); if(audioPlayer.getPlayState() != AudioTrack.PLAYSTATE_PLAYING) audioPlayer.play(); //capture data and record to file int readBytes=0, writtenBytes=0; do{ readBytes = recorder.read(data, 0, bufferSize); if(AudioRecord.ERROR_INVALID_OPERATION != readBytes){ writtenBytes += audioPlayer.write(data, 0, readBytes); } } while(isRecording); </code></pre> <p>It is thrown a java.lang.IllegalStateException with the reason being caused by "play() called on a uninitialized AudioTrack".</p> <p>However, if I change the AudioTrack initialization for example to use sampling rate 8000Hz and sample format 8 bits (instead of 16), it doesn't throw the exception anymore and the application runs, although it produces horrible noise.</p> <p>When I play AudioTrack from a file, there is no problem with the initialization of the AudioTrack, I tried 44100 and 16 bits and it worked properly, producing the correct sound.</p> <p>Any help ?</p>
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