CMSampleBufferSetDataBufferFromAudioBufferList returning error 12731 - ios

Question

I am trying to capture app sound and pass it to AVAssetWriter as input.
I am setting callback for audio unit to get AudioBufferList.
The problem starts with converting AudioBufferList to CMSampleBufferRef.
It always return error -12731 which indicates that required parameter is missing
Thanks Karol
-(OSStatus) recordingCallbackWithRef:(void*)inRefCon
flags:(AudioUnitRenderActionFlags*)flags
timeStamp:(const AudioTimeStamp*)timeStamp
busNumber:(UInt32)busNumber
framesNumber:(UInt32)numberOfFrames
data:(AudioBufferList*)data
{
AudioBufferList bufferList;
bufferList.mNumberBuffers = 1;
bufferList.mBuffers[0].mData = NULL;
OSStatus status;
status = AudioUnitRender(audioUnit,
flags,
timeStamp,
busNumber,
numberOfFrames,
&bufferList);
[self checkOSStatus:status];
AudioStreamBasicDescription audioFormat;
// Describe format
audioFormat.mSampleRate = 44100.00;
audioFormat.mFormatID = kAudioFormatLinearPCM;
audioFormat.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
audioFormat.mFramesPerPacket = 1;
audioFormat.mChannelsPerFrame = 1;
audioFormat.mBitsPerChannel = 16;
audioFormat.mBytesPerPacket = 2;
audioFormat.mBytesPerFrame = 2;
CMSampleBufferRef buff = NULL;
CMFormatDescriptionRef format = NULL;
CMSampleTimingInfo timing = { CMTimeMake(1, 44100), kCMTimeZero, kCMTimeInvalid };
status = CMAudioFormatDescriptionCreate(kCFAllocatorDefault, &audioFormat, 0, NULL, 0, NULL, NULL, &format);
[self checkOSStatus:status];
status = CMSampleBufferCreate(kCFAllocatorDefault,NULL,false,NULL,NULL,format,1, 1, &timing, 0, NULL, &buff);
[self checkOSStatus:status];
status = CMSampleBufferSetDataBufferFromAudioBufferList(buff,
kCFAllocatorDefault,
kCFAllocatorDefault,
0,
&bufferList);
[self checkOSStatus:status]; //Status here is 12731
//Do something with the buffer
return noErr;
}
Edit:
I checked bufferList.mBuffers[0].mData and it is not null so probably that's not a problem.

Answer 1

Since there is a similar question without answer all over the internet.
I managed to solve it and the recording fully works.
My problem was wrong parameter passed to CMSampleBufferCreate.
numSamples instead of 1 should be equal to numberOfFrames.
So the final call is:
CMSampleBufferCreate(kCFAllocatorDefault,NULL,false,NULL,NULL,format,
(CMItemCount)numberOfFrames, 1, &timing, 0, NULL, &buff);