Eu pretendo gravar chamadas com esta aplicação. Mas quando eu definir o audioSource para MediaRecorder.AudioSource.VOICE_CALL, dá um erro, mas quando o audioSource está definido como MediaRecorder.AudioSource.MIC, ele funciona perfeitamente bem. Não tenho certeza onde está o problema. O logcat do problema está abaixo. Qualquer forma de ajuda é muito apreciada. Obrigado.

public class IncomingCallReceiver extends BroadcastReceiver {
private MediaRecorder mRecorder;
@Override
public void onReceive(Context context, Intent intent) {
        Bundle bundle = intent.getExtras();
        if(null == bundle)
                return;
        String state = bundle.getString(TelephonyManager.EXTRA_STATE);
        if(state.equalsIgnoreCase(TelephonyManager.EXTRA_STATE_RINGING))
        {
        }
        else if (state.equalsIgnoreCase(TelephonyManager.EXTRA_STATE_OFFHOOK)){
            Log.i("TelephonyManager", "Call picked up");
            mRecorder = new MediaRecorder();
            mRecorder.setAudioSource(MediaRecorder.AudioSource.VOICE_CALL);
            mRecorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
            mRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
            mRecorder.setAudioEncodingBitRate(16);
            mRecorder.setAudioSamplingRate(44100);
            mRecorder.setOutputFile("/sdcard/Recording/callrecord.mp4");
            try{
                mRecorder.prepare();
            }
            catch(IOException e){
            }
            mRecorder.start();
            Log.i("StartRecordingCall", "Recording Call end");
        }
        else if (state.equalsIgnoreCase(TelephonyManager.EXTRA_STATE_IDLE)){
            Log.i("TelephonyManager", "Call hunged up");
            mRecorder.stop();
            mRecorder.release();
            mRecorder=null;
        }
}

/

    12-18 20:15:56.755: E/MediaRecorder(1577): start failed: -2147483648
    12-18 20:15:56.755: D/AndroidRuntime(1577): Shutting down VM
    12-18 20:15:56.755: W/dalvikvm(1577): threadid=1: thread exiting with uncaught exception (group=0x2b542210)
    12-18 20:15:56.765: E/AndroidRuntime(1577): FATAL EXCEPTION: main
    12-18 20:15:56.765: E/AndroidRuntime(1577): java.lang.RuntimeException: start failed.
    12-18 20:15:56.765: E/AndroidRuntime(1577):     at android.media.MediaRecorder.start(Native Method)
    12-18 20:15:56.765: E/AndroidRuntime(1577):     at com.example.callrecorder.MainActivity.startRecording(MainActivity.java:447)
    12-18 20:15:56.765: E/AndroidRuntime(1577):     at com.example.callrecorder.MainActivity.onClick(MainActivity.java:279)
    12-18 20:15:56.765: E/AndroidRuntime(1577):     at android.view.View.performClick(View.java:3534)
    12-18 20:15:56.765: E/AndroidRuntime(1577):     at android.view.View$PerformClick.run(View.java:14263)
    12-18 20:15:56.765: E/AndroidRuntime(1577):     at android.os.Handler.handleCallback(Handler.java:605)
    12-18 20:15:56.765: E/AndroidRuntime(1577):     at android.os.Handler.dispatchMessage(Handler.java:92)
    12-18 20:15:56.765: E/AndroidRuntime(1577):     at android.os.Looper.loop(Looper.java:137)
    12-18 20:15:56.765: E/AndroidRuntime(1577):     at android.app.ActivityThread.main(ActivityThread.java:4441)
    12-18 20:15:56.765: E/AndroidRuntime(1577):     at java.lang.reflect.Method.invokeNative(Native Method)
    12-18 20:15:56.765: E/AndroidRuntime(1577):     at java.lang.reflect.Method.invoke(Method.java:511)
    12-18 20:15:56.765: E/AndroidRuntime(1577):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
    12-18 20:15:56.765: E/AndroidRuntime(1577):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
    12-18 20:15:56.765: E/AndroidRuntime(1577):     at dalvik.system.NativeStart.main(Native Method)