how to play wave cue markers

Hi

I have a sound with markers and would like to implement standard marker looping functionality. Looks that should be easy with:

AudioClip myClip = AudioClip.Create("MySinoid",44100, 2, 44100, false, true, OnAudioRead, OnAudioSetPosition);

In function OnAudioRead I would like to provide my samples according to markers information, but I have a problem even with playing simple clip properly from the begining to the end.

Can you please tell me why I can't hear begining of my clip or where to set real_pos=0;

 using UnityEngine;
 using System.Collections;
 
 public class clb_test : MonoBehaviour
 {
  int real_pos=0;
  AudioSource looping_src=null;
  public AudioClip source_clip;
  float [] samples = null;
  public bool started=false;
 
  void Start() {
  
  AudioSettings.outputSampleRate=44100;
  looping_src=(AudioSource)gameObject.AddComponent("AudioSource"); 
  looping_src.ignoreListenerVolume = true;
  looping_src.playOnAwake=false;
  looping_src.loop=true;
  
  samples = new float[source_clip.samples * source_clip.channels];
  source_clip.GetData(samples,0);
  
  AudioClip myClip = AudioClip.Create("MySinoid",source_clip.frequency, source_clip.channels, source_clip.frequency, false, true, OnAudioRead, OnAudioSetPosition); 
  looping_src.clip = myClip; 
  
  }
  
     void OnAudioRead(float[] data) 
  {
         int count = 0;
  //string s="T:"+System.DateTime.Now.Second.ToString()+","+System.DateTime.Now.Millisecond.ToString();
  //Debug.Log(s+" real_pos:" +real_pos.ToString());
  
      while (count < data.Length) 
  {
          //data[count] = Mathf.Sign(Mathf.Sin(2 * Mathf.PI * 440 * position / sampleRate));
  
  int len=samples.Length;
  if (real_pos>=len)
  {
  data[count]=0;
  }
  else
  {
  data[count]=samples[real_pos];
  }
  
          count++;
  real_pos++;
  }
     }
     
  void OnAudioSetPosition(int newPosition) 
  {
  //string s="T:"+System.DateTime.Now.Second.ToString()+","+System.DateTime.Now.Millisecond.ToString();
         //Debug.Log("OnAudioSetPosition:"+ s + "new pos "+newPosition.ToString());
  
  if (!started)  //it not helps at all
  {
  real_pos=newPosition;  //If it is here play constantly 1st second of clip which is normal
  started=true;
  }
  
     }
  
  void OnGUI () 
  {
  if(GUILayout.Button("play"))
  {
  started=false;
  //real_pos=0; //if it is here can't hear begining of my clip (check with voice - then easy to detect bug)
  looping_src.Play();
  } 
  
  if(GUILayout.Button("stop"))
  {
  looping_src.Stop();
  started=false;
  }
  }
 }