AudioBufferList *AEAllocateAndInitAudioBufferList(AudioStreamBasicDescription audioFormat, int frameCount) {
int numberOfBuffers = audioFormat.mFormatFlags & kAudioFormatFlagIsNonInterleaved ? audioFormat.mChannelsPerFrame : 1;
int channelsPerBuffer = audioFormat.mFormatFlags & kAudioFormatFlagIsNonInterleaved ? 1 : audioFormat.mChannelsPerFrame;
int bytesPerBuffer = audioFormat.mBytesPerFrame * frameCount;
AudioBufferList *audio = malloc(sizeof(AudioBufferList) + (numberOfBuffers - 1) * sizeof(AudioBuffer));
if (!audio) {
    return NULL;
}
audio->mNumberBuffers = numberOfBuffers;
for (int i = 0; i < numberOfBuffers; i++) {
    if (bytesPerBuffer > 0) {
        audio->mBuffers[i].mData = calloc(bytesPerBuffer, 1);
        if (!audio->mBuffers[i].mData) {
            for (int j = 0; j < i; j++) free(audio->mBuffers[j].mData);
            free(audio);
            return NULL;
        }
    } else {
        audio->mBuffers[i].mData = NULL;
    }
    audio->mBuffers[i].mDataByteSize = bytesPerBuffer;
    audio->mBuffers[i].mNumberChannels = channelsPerBuffer;
}
return audio;}

- (OSStatus)renderToBufferList:(AudioBufferList *)bufferList
               writeToFile:(ExtAudioFileRef)audioFile
              bufferLength:(NSUInteger)bufferLength
                 timeStamp:(AudioTimeStamp *)timeStamp {
[self clearBufferList:bufferList];
AudioUnit outputUnit = self.engine.outputNode.audioUnit;
OSStatus status =AudioUnitRender(outputUnit, 0, timeStamp, 0, (UInt32)bufferLength, bufferList);



float *data1 = bufferList->mBuffers[0].mData;
float *data2 = bufferList->mBuffers[1].mData;;

for(int i=0; i<bufferLength/4; i++)
{
    if(data1[i]!=0||data2[i]!=0)
    NSLog(@"%f - %f",data1[i],data2[i]);
}

if (status != noErr) {
    NSLog(@"Can not render audio unit");
    return status;
}
timeStamp->mSampleTime += bufferLength;
status = ExtAudioFileWrite(audioFile, (UInt32)bufferLength, bufferList);
if (status != noErr)
    NSLog(@"Can not write audio to file");

- (NSString *)renderAudioAndWriteToFile {
    AVAudioOutputNode *outputNode = self.engine.outputNode;
    AudioStreamBasicDescription const *audioDescription = [outputNode outputFormatForBus:0].streamDescription;
    NSString *path = [self filePath];
    ExtAudioFileRef audioFile = [self createAndSetupExtAudioFileWithASBD:audioDescription andFilePath:path];
    if (!audioFile)
        return nil;
    AVURLAsset *asset = [AVURLAsset assetWithURL:self.file.url];
    NSTimeInterval duration = CMTimeGetSeconds(asset.duration);
    NSUInteger lengthInFrames = (NSUInteger) (duration * audioDescription->mSampleRate);

    const NSUInteger kBufferLength = 1024; //3756;

    AudioBufferList *bufferList = AEAllocateAndInitAudioBufferList(*audioDescription, kBufferLength);
    AudioTimeStamp timeStamp;
    memset (&timeStamp, 0, sizeof(timeStamp));
    timeStamp.mFlags = kAudioTimeStampSampleTimeValid;
    OSStatus status = noErr;
    for (NSUInteger i = kBufferLength; i < lengthInFrames; i += kBufferLength) {
        status = [self renderToBufferList:bufferList writeToFile:audioFile bufferLength:kBufferLength timeStamp:&timeStamp];
        if (status != noErr)
            break;
    }
    if (status == noErr && timeStamp.mSampleTime < lengthInFrames) {
        NSUInteger restBufferLength = (NSUInteger) (lengthInFrames - timeStamp.mSampleTime);
        AudioBufferList *restBufferList = AEAllocateAndInitAudioBufferList(*audioDescription, (Float32)restBufferLength);
        status = [self renderToBufferList:restBufferList writeToFile:audioFile bufferLength:restBufferLength timeStamp:&timeStamp];
        AEFreeAudioBufferList(restBufferList);
    }


    SInt64 fileLengthInFrames;
    UInt32 size = sizeof(SInt64);
    ExtAudioFileGetProperty(audioFile, kExtAudioFileProperty_FileLengthFrames, &size, &fileLengthInFrames);
    AEFreeAudioBufferList(bufferList);
    ExtAudioFileDispose(audioFile);
    if (status != noErr)
        [self showAlertWithTitle:@"Error" message:@"See logs for details"];
    else {
        NSLog(@"Finished writing to file at path: %@ n File size must be %f Mb", path,(tmpData.length/1024.0)/1024.0);
        [self showAlertWithTitle:@"Success!" message:@"Now you can play a result file"];
    }
    return path;
}