Audio recording is distorted

[anto gian]

I'm trying to record audio of video-call session. Audio is saved to file but the sound is distorted. Why is this happening? How can I fix it?

Source Code:

/**
 * Implements the AudioRecordSamplesReadyCallback interface and writes
 * recorded raw audio samples to an output file.
 */
public class RecordedAudioToFileController implements SamplesReadyCallback, WebRtcAudioRecord.WebRtcAudioRecordSamplesReadyCallback {
    private static final String TAG = "AUDIO RECORDER";
    private static final long MAX_FILE_SIZE_IN_BYTES = 58348800L * 10;
    private final Object lock = new Object();
    private final ExecutorService executor;
    @Nullable
    private OutputStream rawAudioFileOutputStream;
    private boolean isRunning;
    private long fileSizeInBytes;
    private String audioPath;

    public RecordedAudioToFileController(ExecutorService executor, String audioPath) {
        Log.d(TAG, "ctor");
        this.executor = executor;
        this.audioPath = audioPath;
    }

    /**
     * Should be called on the same executor thread as the one provided at
     * construction.
     */
    public boolean start() {
        Log.d(TAG, "start");
        synchronized (lock) {
            isRunning = true;
        }
        return true;
    }

    /**
     * Should be called on the same executor thread as the one provided at
     * construction.
     */
    public void stop() {
        Log.d(TAG, "stop");
        synchronized (lock) {
            isRunning = false;
            if (rawAudioFileOutputStream != null) {
                try {
                    rawAudioFileOutputStream.close();
                } catch (IOException e) {
                    Log.e(TAG, "Failed to close file with saved input audio: " + e);
                }
                rawAudioFileOutputStream = null;
            }
            fileSizeInBytes = 0;
        }
    }

//    // Checks if external storage is available for read and write.
//    private boolean isExternalStorageWritable() {
//        String state = Environment.getExternalStorageState();
//        return Environment.MEDIA_MOUNTED.equals(state);
//    }

    // Utilizes audio parameters to create a file name which contains sufficient
    // information so that the file can be played using an external file player.
    // Example: /sdcard/recorded_audio_16bits_48000Hz_mono.pcm.
    private void openRawAudioOutputFile(int sampleRate, int channelCount) {
        final File outputFile = new File(audioPath);
        try {
            rawAudioFileOutputStream = new FileOutputStream(outputFile);
        } catch (FileNotFoundException e) {
            Log.e(TAG, "Failed to open audio output file: " + e.getMessage());
        }
        Log.d(TAG, "Opened file for recording: " + audioPath);
    }

    // Called when new audio samples are ready.
    @Override
    public void onWebRtcAudioRecordSamplesReady(JavaAudioDeviceModule.AudioSamples samples) {
        Log.d(TAG, "onWebRtcAudioRecordSamplesReady called with JavaAudioDeviceModule.AudioSamples");
        // The native audio layer on Android should use 16-bit PCM format.
        if (samples.getAudioFormat() != AudioFormat.ENCODING_PCM_16BIT) {
            Log.e(TAG, "Invalid audio format");
            return;
        }
        synchronized (lock) {
            // Abort early if stop() has been called.
            if (!isRunning) {
                return;
            }
            // Open a new file for the first callback only since it allows us to add audio parameters to
            // the file name.
            if (rawAudioFileOutputStream == null) {
                openRawAudioOutputFile(samples.getSampleRate(), samples.getChannelCount());
                fileSizeInBytes = 0;
            }
        }
        // Append the recorded 16-bit audio samples to the open output file.
        executor.execute(() -> {
            if (rawAudioFileOutputStream != null) {
                try {
                    // Set a limit on max file size. 58348800 bytes corresponds to
                    // approximately 10 minutes of recording in mono at 48kHz.
                    if (fileSizeInBytes < MAX_FILE_SIZE_IN_BYTES) {
                        // Writes samples.getData().length bytes to output stream.
                        rawAudioFileOutputStream.write(samples.getData());
                        fileSizeInBytes += samples.getData().length;
                    }
                } catch (IOException e) {
                    Log.e(TAG, "Failed to write audio to file: " + e.getMessage());
                }
            }
        });
    }

    // Called when new audio samples are ready.
    @Override
    public void onWebRtcAudioRecordSamplesReady(WebRtcAudioRecord.AudioSamples samples) {
        Log.d(TAG, "onWebRtcAudioRecordSamplesReady called with WebRtcAudioRecord.AudioSamples");
        onWebRtcAudioRecordSamplesReady(new JavaAudioDeviceModule.AudioSamples(samples.getAudioFormat(),
                samples.getChannelCount(), samples.getSampleRate(), samples.getData()));
    }
}

[Corey Cole]

When you say the recording is distorted, is it anything like the call audio? Is the file duration the same as the call duration?