Android AudioRecord - Record Audio with small file size

Question

I'm working on Audio recorder app using AudioRecord not MediaRecorder. I'm writing this code to record:

private void startRecord(){

        File file = new File(Environment.getExternalStorageDirectory(), "test.pcm");

        try {
            file.createNewFile();

            OutputStream outputStream = new FileOutputStream(file);
            BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(outputStream);
            DataOutputStream dataOutputStream = new DataOutputStream(bufferedOutputStream);

            int minBufferSize = AudioRecord.getMinBufferSize(8000,
                    AudioFormat.CHANNEL_CONFIGURATION_MONO,
                    AudioFormat.ENCODING_PCM_16BIT);

            short[] audioData = new short[minBufferSize];

            AudioRecord audioRecord = new AudioRecord(MediaRecorder.AudioSource.MIC,
                    8000,
                    AudioFormat.CHANNEL_CONFIGURATION_MONO,
                    AudioFormat.ENCODING_PCM_16BIT,
                    minBufferSize);

            audioRecord.startRecording();

            while(recording){
                int numberOfShort = audioRecord.read(audioData, 0, minBufferSize);
                for(int i = 0; i < numberOfShort; i++){
                    dataOutputStream.writeShort(audioData[i]);
                }
            }

            audioRecord.stop();
            dataOutputStream.close();

        } catch (IOException e) {
            e.printStackTrace();
        }

    }

It's working fine. but, i have a large file size. I recorded about 1 min and i had file with size about 1.2M.

I tried to use MediaRecorder using this code:

mMediaRecorder = new MediaRecorder();

mMediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);

mMediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);

mMediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);

mMediaRecorder.setOutputFile(fileName);

mMediaRecorder.prepare();

mMediaRecorder.start();

It's great and recorded 5 minutes with file size about 500K or less. But, i have to use AudioRecord because i need to apply some task on audio byte by byte.

Can i have the same file size in MediaRecorder when i use AudioRecord?

Thank you very much.

akaish akaish · Accepted Answer · 2016-09-18T07:09:02

Actually with AudioRecord class you get raw data from sound source without any compression to byte buffer you work with and MediaRecorder class provides only basic functionality for recording media from any available sources without direct access to data buffers.

I assume you should use AudioRecord for capturing audio, apply your byte to byte task for data in AudioRecord buffer and then write modified data from buffer using compression to a file. As I remember, there is no already implemented functionality in android API for audio compression, so you should use third-party library (for example lame) or write compression yourself. You can check this sources for audio recording in MP3 with lame: https://github.com/yhirano/Mp3VoiceRecorderSampleForAndroid

Android AudioRecord - Record Audio with small file size

1 Answers