CMSampleBuffer's audio format changes when coming from the background

Hi,

I'm capturing Audio and Video using AVFoundation's AVCaptureSession using the AVCaptureVideoDataOutputSampleBufferDelegate & AVCaptureAudioDataOutputSampleBufferDelegate to collect CMSampleBuffers and write them to file using AVAssetWriter.

The issues I'm facing is that while recording if the user goes to the background and returns, the CMSampleBuffer's AudioFormat changes from:

this

•   FormatList Array: {
    	Index: 0 
    	ChannelLayoutTag: 0x640001 
    	ASBD: {
    	mSampleRate: 48000.000000 
    	mFormatID: 'lpcm' 
    	mFormatFlags: 0xc 
    	mBytesPerPacket: 2 
    	mFramesPerPacket: 1 
    	mBytesPerFrame: 2 
    	mChannelsPerFrame: 1 
    	mBitsPerChannel: 16 	}} 
  

to this:

•   FormatList Array: {
    	Index: 0 
    	ChannelLayoutTag: 0x640001 
    	ASBD: {
    	mSampleRate: 48000.000000 
    	mFormatID: 'lpcm' 
    	mFormatFlags: 0xc 
    	mBytesPerPacket: 8 
    	mFramesPerPacket: 1 
    	mBytesPerFrame: 8 
    	mChannelsPerFrame: 4 
    	mBitsPerChannel: 16 	}} 
  

This obviously creates an issue with the AudioInput in the AVAssetWriter and fails the writing

Does anyone have an idea what going on?

As to the CaptureSession setup:

• Inputs:

Front / back camera & internal microphone

• outputs:

AVCaptureVideoDataOutput & AVCaptureAudioDataOutput

I am changing the active format in the videoInput's device when I start the session

Thanks, Yoav