Converting MP3 to PCM and playing it back in Android

Question

I am trying to convert an mp3 file to pcm file and trying to play it. I want the values as int16. I was able to successfully convert it using MediaCodec and MediaExtractor in android. And i was able to play it back normally(I had to change the sample rate to play PCM) while i was writing it directly as byte array like this:

override fun onOutputBufferAvailable(codec: MediaCodec, index: Int, info: MediaCodec.BufferInfo) {
            Log.d(TAG, "onOutputBufferAvailable")
            val buffer = mediaCodec.getOutputBuffer(index)
            val b = ByteArray(info.size - info.offset)
            val a = buffer.position()
            buffer.get(b)
            buffer.position(a)
            mediaCodec.releaseOutputBuffer(index, true)
            Log.i(TAG,"byte data: "+b.contentToString())
            fos.write(b,0,info.size-info.offset)
        }

But as I said I want it as Int16 (i am under the impression that this can just be converted to int and saved. please correct me if i am wrong) and when i save it as int like this

override fun onOutputBufferAvailable(codec: MediaCodec, index: Int, info: MediaCodec.BufferInfo) {
            Log.d(TAG, "onOutputBufferAvailable")
            val buffer = mediaCodec.getOutputBuffer(index)
            val byteArray = ByteArray(info.size - info.offset)
            val bufferPosition = buffer.position()
            buffer.get(byteArray)
            buffer.position(bufferPosition)
            mediaCodec.releaseOutputBuffer(index, true)
            for (i in byteArray){
                Log.i(TAG,"byte data: "+i.toInt())
                fileWriter.write(i.toString()+" ")
            }
        }

it is filled with noise. I need it as int so that i can do some manipulation to the audio file. If you want to check out the whole project it is in github

I want to know how i can properly write pcm file as int values and play it back in android. Thanks in advance