How to solve no sound output from virtual audio device(BlackHole 2ch) when I use BlackHole to capture system output audio on Mac?

Question

I have a conundrum:

I'm using BlackHole try to capture system output audio on macOS, BlackHole drive can create an virtual audio device, like BlackHole 2ch, which supports 2 channels.
when I select this virtual device as audio output device, I do really can capture system output audio through a corresponding virtual input device created by BlockHole at the same time with virtual output device.

But, there is no sound playback from virtual output device, I cannot hear any voice from speaker or headphone.
I know it must be write some lines of code in BlackHole_DoIOOperation() function, but I don't know any direction, can anyone give me some suggestion? Thanks

This is virtual output device created by BlackHole

This is virtual input device created by BlackHole

here is BlackHole_DoIOOperation() function source code:
I suspect caused by this line of code, so I removed it, but still doesn't work.
// memset(ioMainBuffer, 0, inIOBufferFrameSize * NUMBER_OF_CHANNELS * sizeof(Float32));

static OSStatus BlackHole_DoIOOperation(AudioServerPlugInDriverRef          inDriver,
                                        AudioObjectID                       inDeviceObjectID,
                                        AudioObjectID                       inStreamObjectID,
                                        UInt32                              inClientID,
                                        UInt32                              inOperationID,
                                        UInt32                              inIOBufferFrameSize,
                                        const AudioServerPlugInIOCycleInfo* inIOCycleInfo,
                                        void*                               ioMainBuffer,
                                        void*                               ioSecondaryBuffer)
{
    //  This is called to actuall perform a given operation. For this device, all we need to do is
    //  clear the buffer for the ReadInput operation.
    DebugMsg("BlackHole DoIOOperation()");
    #pragma unused(inClientID, inIOCycleInfo, ioSecondaryBuffer)
    
    //  declare the local variables
    OSStatus theAnswer = 0;
    
    //  check the arguments
    FailWithAction(inDriver != gAudioServerPlugInDriverRef, theAnswer = kAudioHardwareBadObjectError, Done, "BlackHole_DoIOOperation: bad driver reference");
    FailWithAction(inDeviceObjectID != kObjectID_Device, theAnswer = kAudioHardwareBadObjectError, Done, "BlackHole_DoIOOperation: bad device ID");
    FailWithAction((inStreamObjectID != kObjectID_Stream_Input) && (inStreamObjectID != kObjectID_Stream_Output), theAnswer = kAudioHardwareBadObjectError, Done, "BlackHole_DoIOOperation: bad stream ID");
    
    // IO Lock
    pthread_mutex_lock(&gDevice_IOMutex);

    // From BlackHole to Application
    if(inOperationID == kAudioServerPlugInIOOperationReadInput)
    {

        Float32* buffer = (Float32*)ioMainBuffer;
        UInt64 mSampleTime = inIOCycleInfo->mInputTime.mSampleTime;

        for (UInt32 frame = 0; frame < inIOBufferFrameSize; frame++)
        {
            for (int channel = 0; channel < NUMBER_OF_CHANNELS; channel++)
            {
                // don't do anything if muted
                if (!gMute_Output_Master_Value)
                {
                    // write to the ioMainBuffer
                    buffer[frame*NUMBER_OF_CHANNELS+channel] = ringBuffer[((mSampleTime+frame)%kDevice_RingBufferSize)*NUMBER_OF_CHANNELS+channel];
                }
                else
                {
                    buffer[frame*NUMBER_OF_CHANNELS+channel] = 0;
                }
                
                // clear ring buffer after 8192 samples.
                ringBuffer[((mSampleTime+frame-8192)%kDevice_RingBufferSize)*NUMBER_OF_CHANNELS+channel] = 0;

            }
        }
    }
    
    // From Application to BlackHole
    if(inOperationID == kAudioServerPlugInIOOperationWriteMix)
    {
        DebugMsg("output...");
        Float32* buffer = (Float32*) ioMainBuffer;
        UInt64 mSampleTime = inIOCycleInfo->mOutputTime.mSampleTime;
        for (UInt32 frame = 0; frame < inIOBufferFrameSize; frame++)
        {
            for (int channel = 0; channel < NUMBER_OF_CHANNELS; channel++)
            {
                // don't do anything if muted
                if (!gMute_Output_Master_Value)
                {
                    // write to internal ring buffer
                    DebugMsg("channel: %d", channel);
                    ringBuffer[((mSampleTime + frame) % kDevice_RingBufferSize) * NUMBER_OF_CHANNELS + channel] += buffer[frame * NUMBER_OF_CHANNELS + channel] * gVolume_Output_Master_Value;
                }
                else
                {
                    buffer[frame * NUMBER_OF_CHANNELS + channel] = 0;
                }
                
                // clear ring buffer after 8192 samples.
                ringBuffer[((mSampleTime + frame - 8192) % kDevice_RingBufferSize) * NUMBER_OF_CHANNELS + channel] = 0;
            }
        }
        theAnswer = kAudioHardwareBadObjectError;
        
        // clear the io buffer
        // memset(ioMainBuffer, 0, inIOBufferFrameSize * NUMBER_OF_CHANNELS * sizeof(Float32));
    }
    
    pthread_mutex_unlock(&gDevice_IOMutex);

Done:
    return theAnswer;
}