Bug Short sounds (ex: 1/4 s) plays twice the first time, if the audioClip is created in streaming mode.

Hi, I wonder if I am missing something here, or if this is a bug to report...

Creating a short AudioClip in code, as in https://docs.unity3d.com/ScriptReference/AudioClip.Create.html, causes the sound to be played twice first, and once (as expected) on subsequent Play() calls.

To reproduce, simply create an empty 3d project, attach a script to the camera, and paste the following:

Code (CSharp):

1. public class NewBehaviourScript : MonoBehaviour
2. {
3.     /// <summary>
4.     /// This example is closely based on the Unity documentation for AudioClip.Create: https://docs.unity3d.com/ScriptReference/AudioClip.Create.html
5.     /// Short sounds (ex: 1/4 s) plays twice the first time, if the audioClip is created in streaming mode.
6.     /// Unity 2020.3.17f1, default empty 3d project, with one single script added (this one).
7.     /// </summary>
8.     void Start()
9.     {
10.         // Create a 1/4 s sound. (if I use a 1s sound -samplerate / 1-, everything works fine)
11.         _Pcm = new float[samplerate / 4];
12.  
13.         // Fill the first half with a 440Hz frequency, leave the second half silent.
14.         int count = 0;
15.         while (count < _Pcm.Length / 2)
16.         {
17.             _Pcm[count] = Mathf.Sin(2 * Mathf.PI * frequency * position / samplerate);
18.             position++;
19.             count++;
20.         }
21.  
22.         _AudioSource = Camera.main.gameObject.AddComponent<AudioSource>();
23.  
24.         // Creating the audioClip in streaming mode causes the issue.
25.         _AudioSource.clip = AudioClip.Create("", _Pcm.Length, channels: 1, samplerate, stream: true, OnAudioRead, OnAudioSetPosition);
26.  
27.         // If instead of using streaming, I pass the pcm data to SetData(...), everything works fine.
28.         //_AudioSource.clip = AudioClip.Create("", _Pcm.Length, channels: 1, samplerate, stream: false);
29.         //_AudioSource.clip.SetData(_Pcm, 0);
30.     }
31.  
32.     void OnAudioRead(float[] data)
33.     {
34.         Array.Copy(_Pcm, position, data, 0, data.Length);
35.         position += data.Length;
36.     }
37.  
38.     void OnAudioSetPosition(int newPosition)
39.     {
40.         position = newPosition;
41.     }
42.  
43.     public int position = 0;
44.     public int samplerate = 44100;
45.     public float frequency = 440;
46.  
47.     AudioSource _AudioSource;
48.     float[] _Pcm;
49.  
50.     void Update()
51.     {
52.         // In stream mode, the first F2 hit plays the sound twice, while all the following F2 hits play the sound only once (as expected).
53.         if (Input.GetKeyDown(KeyCode.F2))
54.         {
55.             _AudioSource.Play();
56.         }
57.     }
58. }

 

Just tried with Unity 2020.3.23f1: same behavior.