Format error setting up AudioQueue for recording, but only happens once in a while - ios

Question

So oddly, this error happens only once in a while, when we are setting up the audio queue (even though I'm doing everything the same way). Device iPhone 5, iOS8.3:
mediaserverd[37] <Error>: 15:14:24.594 ERROR: [0x2883000] >aq> 323: AudioConverterNew from AudioQueueNew returned 'fmt?'
io: 0 ch, 44100 Hz, 'lpcm' (0x00000029) 32-bit little-endian float, deinterleaved
client: 0 ch, 44100 Hz, 'lpcm' (0x0000000C) 16-bit signed integer
Here's the code that triggers it.
SetupAudioFormat(kAudioFormatLinearPCM);
// create the queue
XThrowIfError(AudioQueueNewInput(
&mRecordFormat,
MyInputBufferHandler,
this /* userData */,
NULL /* run loop */, NULL /* run loop mode */,
0 /* flags */, &mQueue), "AudioQueueNewInput failed");
where mRecordFormat is setup like:
void AQRecorder::SetupAudioFormat(UInt32 inFormatID)
{
memset(&mRecordFormat, 0, sizeof(mRecordFormat));
UInt32 size = sizeof(mRecordFormat.mSampleRate);
mRecordFormat.mSampleRate=[AVAudioSession sharedInstance].sampleRate;
size = sizeof(mRecordFormat.mChannelsPerFrame);
mRecordFormat.mChannelsPerFrame=(UInt32)[AVAudioSession sharedInstance].inputNumberOfChannels;
mRecordFormat.mFormatID = inFormatID;
mRecordFormat.mBytesPerFrame =mRecordFormat.mChannelsPerFrame * sizeof (SInt16);
if (inFormatID == kAudioFormatLinearPCM)
{
// if we want pcm, default to signed 16-bit little-endian
mRecordFormat.mFormatFlags = kLinearPCMFormatFlagIsSignedInteger | kLinearPCMFormatFlagIsPacked;
mRecordFormat.mBitsPerChannel = 16;
mRecordFormat.mBytesPerPacket = mRecordFormat.mBytesPerFrame = (mRecordFormat.mBitsPerChannel / 8) * mRecordFormat.mChannelsPerFrame;
mRecordFormat.mFramesPerPacket = 1;
} else if(inFormatID==kAudioFileAIFFType) {
mRecordFormat.mFramesPerPacket = 1;
mRecordFormat.mFormatFlags =
kLinearPCMFormatFlagIsBigEndian
| kLinearPCMFormatFlagIsSignedInteger
| kLinearPCMFormatFlagIsPacked;
}
}
My interpretation of the error is that the phone is recording as 32-bit little-endian float, deinterleaved and I'm trying to setup a queue with a format that is 16-bit signed integer. But why don't I get the error everytime? How to fix it?

Answer 1

AudioStreamBasicDescriptions are really annoying. Here is what I use. I have typedefed AudioStreamBasicDescription to ASBD
ASBD asbdWithInfo(Boolean isFloat,int numberOfChannels,Boolean interleavedIfStereo){
ASBD asbd = {0};
int sampleSize = isFloat ? sizeof(float) : sizeof(SInt16);
asbd.mChannelsPerFrame = (numberOfChannels == 1) ? 1 : 2;
asbd.mBitsPerChannel = 8 * sampleSize;
asbd.mFramesPerPacket = 1;
asbd.mSampleRate = 44100.0;
asbd.mBytesPerFrame = interleavedIfStereo ? sampleSize * asbd.mChannelsPerFrame : sampleSize;
asbd.mBytesPerPacket = asbd.mBytesPerFrame;
asbd.mReserved = 0;
asbd.mFormatID = kAudioFormatLinearPCM;
if (isFloat) {
asbd.mFormatFlags = kAudioFormatFlagIsFloat;
if (interleavedIfStereo) {
if (numberOfChannels == 1) {
asbd.mFormatFlags = asbd.mFormatFlags | kAudioFormatFlagsNativeEndian | kAudioFormatFlagIsPacked | kAudioFormatFlagIsNonInterleaved;
}
}
else{
asbd.mFormatFlags = asbd.mFormatFlags | kAudioFormatFlagIsNonInterleaved | kAudioFormatFlagIsPacked ;
}
}
else{
asbd.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagsNativeEndian | kAudioFormatFlagIsPacked;
if (!interleavedIfStereo) {
if (numberOfChannels > 1) {
asbd.mFormatFlags = asbd.mFormatFlags | kAudioFormatFlagIsNonInterleaved;
}
}
}
return asbd;
}