# pcmreadcallback never is called during playback

**URL:** <https://qa.fmod.com/t/pcmreadcallback-never-is-called-during-playback/11770>\
**Category:** Unity\
**Created:** [December 20, 2014, 3:41am UTC](https://qa.fmod.com/t/pcmreadcallback-never-is-called-during-playback/11770 "2014-12-20T03:41:45Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![wadrwadr](https://avatars.discourse-cdn.com/v4/letter/w/7993a0/32.png) [@wadrwadr](https://qa.fmod.com/u/wadrwadr)\
**Post date:** [December 20, 2014, 3:41am UTC](https://qa.fmod.com/t/pcmreadcallback-never-is-called-during-playback/11770/1 "2014-12-20T03:41:45Z")

</div>

Hello Guys,

I’m writing a Unity class to playback and capture audio data from a microphone.  
Playback part works fine I can hear my voice in the headphones but I cannot access audio samples because pcmsetposcallback is never called during playback.  
It is called only once inside createSound method.  
I think i’m missing some setting , also tried several OR combinations for FMOD.MODE flag but with no luck.

Thanks in advance.  
Walter

public class AudioInit : MonoBehaviour {

```
FMOD.System lowlevel = null;
FMOD.Sound snd = null;

// callbacks delegates
FMOD.SOUND_PCMREADCALLBACK pcmreadcallbackPtr = new FMOD.SOUND_PCMREADCALLBACK (pcmreadcallbackFunc);
FMOD.SOUND_PCMSETPOSCALLBACK pcmsetposcallbackPtr = new FMOD.SOUND_PCMSETPOSCALLBACK(pcmsetposcallbackFunc);
int driverId;

// Use this for initialization
void Start () {

	int channels = 1;
	int sampleRate = 8000;
	float recordTime = 1.0f;

	// get low level instance
	FMOD_StudioSystem.instance.System.getLowLevelSystem(out lowlevel);

	// fill sound info struct
	FMOD.CREATESOUNDEXINFO soundInfo = new FMOD.CREATESOUNDEXINFO ();		
	soundInfo.cbsize = System.Runtime.InteropServices.Marshal.SizeOf (typeof(FMOD.CREATESOUNDEXINFO));
	soundInfo.length = (uint)(sampleRate * channels * sizeof(byte) * recordTime);		
	soundInfo.numchannels = channels;
	soundInfo.defaultfrequency = sampleRate;
	soundInfo.format = FMOD.SOUND_FORMAT.PCM8;
	soundInfo.pcmreadcallback = pcmreadcallbackPtr;
	soundInfo.pcmsetposcallback = pcmsetposcallbackPtr;
	soundInfo.dlsname = IntPtr.Zero;

	// FMODE MODE flag
	FMOD.MODE mode = FMOD.MODE.OPENUSER | FMOD.MODE.LOOP_NORMAL;

	// create sound
	FMOD.RESULT res = lowlevel.createSound((string)null, mode, ref soundInfo, out snd);
	
	if (res != FMOD.RESULT.OK) {
		Debug.Log ("ERROR snd " + res.ToString ());
		return;
	}

	// get driver
	res = lowlevel.getDriver (out driverId);		
	if (res != FMOD.RESULT.OK) {
		Debug.Log ("ERROR getDriver " + res.ToString ());
		return;
	}

	// start record from microphone
	res = lowlevel.recordStart (driverId, snd, true);		
	if (res != FMOD.RESULT.OK) {
		Debug.Log ("ERROR recordStart " + res.ToString ());
		return;
	}

	uint pos = 0;
	uint tries = 10;
	// wait for a valid record position
	while ( !(pos > 0) && (tries--) > 0 ) {

		if ( lowlevel.getRecordPosition(driverId, out pos) == FMOD.RESULT.OK ){
			System.Threading.Thread.Sleep(100);
		} else { break; }
	}
	if ( !( pos > 0 )) {
		Debug.Log ("ERROR invalid record position");
		return;
	}

	// start playback
	FMOD.Channel chn;
	res = lowlevel.playSound (snd, new FMOD.ChannelGroup (IntPtr.Zero), false, out chn);

	if (res != FMOD.RESULT.OK) {
		Debug.Log ("ERROR recordStart " + res.ToString ());
		return;
	}

}

// not used
static FMOD.RESULT pcmsetposcallbackFunc(IntPtr soundraw, int subsound, uint position, FMOD.TIMEUNIT postype)
{
	return FMOD.RESULT.OK;
}

// only called once during lowlevel.createSound execution 
static FMOD.RESULT pcmreadcallbackFunc (IntPtr sound, IntPtr data, uint len){
	
	Debug.Log("pcmreadcallback sample size " + len.ToString());
	return FMOD.RESULT.OK;
}

// Update is called once per frame
void Update () {
}

```

}

---

<div class="post-metadata">

**Author:** ![nick1](https://avatars.discourse-cdn.com/v4/letter/n/47e85d/32.png) [@nick1](https://qa.fmod.com/u/nick1)\
**Post date:** [January 5, 2015, 6:28am UTC](https://qa.fmod.com/t/pcmreadcallback-never-is-called-during-playback/11770/2 "2015-01-05T06:28:50Z")

</div>

Those callbacks aren’t what you want.

Each frame use System.getRecordPosition() to track how much audio has been recorded since the last frame, and then use Sound.@lock() to get a pointer to the data and copy it out. Be aware you’ll have to deal with the buffer wrapping around.