Android: unable to indentify recorded track

My purpose is to identify the song artist uploading 10s recorded track from an Android device.

I record the track using:

recorder = new MediaRecorder();
recorder.setAudioSource(MediaRecorder.AudioSource.CAMCORDER);
recorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
recorder.setAudioEncoder(MediaRecorder.AudioEncoder.AAC);
recorder.setAudioEncodingBitRate(256000);
recorder.setAudioSamplingRate(48000);
recorder.setOutputFile(audioFileName);
recorder.setMaxDuration(duration * 1000);

the upload goes well, but I never get the info back in the response. I try 10s, 20s and more. I also try playing with the recorder parameters without any result.

The response I got from the API is

{
    status : {
        version : "4.2",
        code : 0,
        message : "Success"
    },
    track : {
        status : "pending",
        artist : null,
        title : null,
        release : "",
        audio_md5 : "2819c6b48f55b70590bb432c8894db0b",
        bitrate : **160**,
        id : "TRYTNFK149900511A1",
        samplerate : **32000**,
        md5 : "2819c6b48f55b70590bb432c8894db0b"
    }
}

FFMpeg output for the file is

Duration: 00:00:10.03, start: 0.000000, bitrate: **191** kb/s
    Stream #0:0(eng): Audio: aac (mp4a / 0x6134706D), **48000** Hz, mono, fltp, 189 kb/s (default)

So what's wrong with the file? Why the response rate values are different from the FFMpeg output?

Even if the audio quality seams quite good, I never got the artist name.