# I use FMOD\_OUTPUTTYPE\_WAVWRITER\_NRT, but not work

**URL:** <https://qa.fmod.com/t/i-use-fmod-outputtype-wavwriter-nrt-but-not-work/11991>\
**Category:** FMOD Engine\
**Created:** [July 17, 2015, 6:43am UTC](https://qa.fmod.com/t/i-use-fmod-outputtype-wavwriter-nrt-but-not-work/11991 "2015-07-17T06:43:26Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![qq200600](https://avatars.discourse-cdn.com/v4/letter/q/c77e96/32.png) [@qq200600](https://qa.fmod.com/u/qq200600)\
**Post date:** [July 17, 2015, 6:43am UTC](https://qa.fmod.com/t/i-use-fmod-outputtype-wavwriter-nrt-but-not-work/11991/1 "2015-07-17T06:43:26Z")

</div>

```
result = system->setOutput(FMOD_OUTPUTTYPE_WAVWRITER_NRT);
    ERRCHECK(result);
    
   char cDest[200] = {0};
    NSString *fileName=[NSString stringWithFormat:@"%@/addeffects_sound.wav", [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0]];
    [fileName getCString:cDest maxLength:200 encoding:NSASCIIStringEncoding];
    
    printf(fileName.cString);
    result = system->init(32, FMOD_INIT_NORMAL, cDest);
    
   // result = system->init(32, FMOD_INIT_NORMAL, extradriverdata);
    //ERRCHECK(result);

    result = system->getMasterChannelGroup(&mastergroup);
    ERRCHECK(result);

    result = system->createSound(Common_MediaPath("drumloop.wav"), FMOD_DEFAULT, 0, &sound);
    ERRCHECK(result);

    result = system->playSound(sound, 0, false, &channel);
    ERRCHECK(result);

```

////I add up code to effects.cpp, and it will create addeffects\_sound.wav. and i add dap to it. but can not play . why? please help me

---

<div class="post-metadata">

**Author:** ![mathew](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/mathew/32/431_2.png) [@mathew](https://qa.fmod.com/u/mathew)\
**Post date:** [July 19, 2015, 11:33pm UTC](https://qa.fmod.com/t/i-use-fmod-outputtype-wavwriter-nrt-but-not-work/11991/2 "2015-07-19T23:33:56Z")

</div>

You need to call System::update to operate the non-realtime version of wav writer. Each call to System::update will generate 1 DSP block of samples which is usually 1024 samples.