core audio offline rendering issue on iOS 8

I want to apply reverb effect on a sound file and want to save it on disk using Core Audio. I successfully apply the effect and played it using kAudioUnitSubType_RemoteIO. Now I want to save it on disk so I use kAudioUnitSubType_GenericOutput and call AudioUnitRender and I used same code listed below.

Triggering UI code from Audio Unit Render Proc on iOS

Now Problem is that when I run same code from above link on iOS7 it works fine. When I run it on iOS 8 device it simply save a file having no sound. Can any one help me?

Thanks