AudioRecord start() error status -38

Question

I'm trying to set up an audio recorder and I keep getting a specific error and I can't figure out why. in my code I have checked what state the audio recorder is in with the Log before and after the startrecording() method.

ar = new AudioRecord(audiosource, sampleRate, channelConfiguration,
                audioEncoding, buffersizebytes);
Log.d("info", "ar.getState() before = " + String.valueOf(ar.getState()));
ar.startRecording();
Log.d("info", "ar.getState() after = " +String.valueOf(ar.getState()));

When I run the app I'm getting these messages in logcat.

D/info﹕ ar.getState() before = 1
E/AudioRecord﹕ start() status -38
D/info﹕ ar.getState() after = 1

from what I have read in the documentation the state 1 can either correspond to the audio recorder being in the RECORDSTATE_STOPPED or the STATE_INITIALIZED states neither of these two should cause a problem when calling startRecording().

The status -38 I believe is a errno.h code for /* Function not implemented */ is this referring to the startRecording() method or as it states in the error the start() function which is not a method for the AudioRecorder class.

I have tried multiple methods to make sure that the release() function was called so I don't think that is the problem here.

Any help is greatly appreciated.

Answer 1

alright so this is what i think i needed to do this should really be talked about in the AudioRecorder documentation but this similar questioin led me to the answer AudioRecord object not initializing basically what you want to do is loop through all the configurations and try each against the AudioRecord.ERROR_BAD_VALUE check also since I was planning on using a fft in which the length must be a power of 2 i added a little if else if portion if anybody else runs into a similar situation

public AudioRecord findAudioRecord() {
    for (int rate : mSampleRates) {
        for (short audioFormat : new short[]{AudioFormat.ENCODING_PCM_8BIT, AudioFormat.ENCODING_PCM_16BIT}) {
            for (short channelConfig : new short[]{AudioFormat.CHANNEL_IN_MONO, AudioFormat.CHANNEL_IN_STEREO}) {
                try {
                    //Log.d("audioSetup", "Attempting rate " + rate + "Hz, bits: " + audioFormat + ", channel: " + channelConfig);
                    int bufferSize = AudioRecord.getMinBufferSize(rate, channelConfig, audioFormat);
                    if (bufferSize > 0 && bufferSize <= 256){
                        bufferSize = 256;
                    }else if (bufferSize > 256 && bufferSize <= 512){
                        bufferSize = 512;
                    }else if (bufferSize > 512 && bufferSize <= 1024){
                        bufferSize = 1024;
                    }else if (bufferSize > 1024 && bufferSize <= 2048){
                        bufferSize = 2048;
                    }else if (bufferSize > 2048 && bufferSize <= 4096){
                        bufferSize = 4096;
                    }else if (bufferSize > 4096 && bufferSize <= 8192){
                        bufferSize = 8192;
                    }else if (bufferSize > 8192 && bufferSize <= 16384){
                        bufferSize = 16384;
                    }else{
                        bufferSize = AudioRecord.getMinBufferSize(rate, channelConfig, audioFormat);
                    }

                    if (bufferSize != AudioRecord.ERROR_BAD_VALUE) {
                        // check if we can instantiate and have a success
                        AudioRecord recorder = new AudioRecord(MediaRecorder.AudioSource.DEFAULT, rate, channelConfig, audioFormat, bufferSize);

                        if (recorder.getState() == AudioRecord.STATE_INITIALIZED) {
                            Log.d("found", "rate: " + rate + " channelConfig: " + channelConfig + " bufferSize: " + bufferSize + " audioFormat: " + audioFormat);
                            sampleRate = rate;
                            channelConfiguration = channelConfig;
                            audioEncoding = audioFormat;
                            buffersizebytes = bufferSize;
                            return recorder;
                        }
                    }
                } catch (Exception e) {
                    Log.d("audioSetup", rate + "Exception, keep trying.", e);
                    e.printStackTrace();
                }
            }
        }
    }
    return null;
}

seems to work nicely. thanks for the help.