Why I get multiple bounding box

HI,

I'm trying to draw one bbox on my screen, but I don't know why it comes out several bbox like below.

Here is my code.

Ptr<IMetadataPacket> DeviceAgent::generateObjectMetadataPacket()
{
    // ObjectMetadataPacket contains arbitrary number of ObjectMetadata.
    const auto objectMetadataPacket = makePtr<ObjectMetadataPacket>();

    // Bind the object metadata to the last video frame using a timestamp.
    objectMetadataPacket->setTimestampUs(last_video_frame_timestampUs_);
    objectMetadataPacket->setDurationUs(0);

    //for( size_t i = 0; i < this->object_size_; i++ ){

    //    const auto object_metadata = makePtr<ObjectMetadata>();

    //    object_metadata->setTypeId( "nx.sample.helloWorld" );

    //    auto track_id = nx::sdk::UuidHelper::fromStdString( std::to_string( this->object_list_[i].nObjectID ) );

    //    //auto track_id = nx::sdk::UuidHelper::randomUuid();

    //    object_metadata->setTrackId( track_id );

    //    float x = this->object_list_[i].nX / (float)this->video_width_;

    //    float y = this->object_list_[i].nY / (float)this->video_height_;

    //    float width = this->object_list_[i].nWidth / (float)this->video_width_;

    //    float height = this->object_list_[i].nHeight / (float)this->video_height_;

    //    object_metadata->setBoundingBox( Rect( x, y, width, height ) );

    //    objectMetadataPacket->addItem( object_metadata.get() );

    //    DumpDebugMessage( "x:%f y:%f object id:%d uuid:%d", x, y, this->object_list_[i].nObjectID, track_id );

    //}

    if( this->object_size_ != 0 ){
        int i = 0;

        const auto object_metadata = makePtr<ObjectMetadata>();

        object_metadata->setTypeId( "nx.sample.helloWorld" );

        //auto track_id = nx::sdk::UuidHelper::fromStdString( std::to_string( this->object_list_[i].nObjectID ) );

        auto track_id = nx::sdk::UuidHelper::randomUuid();

        object_metadata->setTrackId( track_id );

        float x = this->object_list_[i].nX / (float)this->video_width_;

        float y = this->object_list_[i].nY / (float)this->video_height_;

        float width = this->object_list_[i].nWidth / (float)this->video_width_;

        float height = this->object_list_[i].nHeight / (float)this->video_height_;

        object_metadata->setBoundingBox( Rect( x, y, width, height ) );

        objectMetadataPacket->addItem( object_metadata.get() );
    }

    //// ObjectMetadata contains information about an object on the frame.
    //const auto objectMetadata = makePtr<ObjectMetadata>();
    //// Set all required fields.
    //objectMetadata->setTypeId(kHelloWorldObjectType);
    //objectMetadata->setTrackId(m_trackId);

    //// Calculate bounding box coordinates each frame so that it moves from the top left corner
    //// to the bottom right corner during kTrackFrameCount frames.
    //static constexpr float d = 0.5F / kTrackFrameCount;
    //static constexpr float width = 0.5F;
    //static constexpr float height = 0.5F;
    //const int frameIndexInsideTrack = m_frameIndex % kTrackFrameCount;
    //const float x = d * frameIndexInsideTrack;
    //const float y = d * frameIndexInsideTrack;
    //objectMetadata->setBoundingBox(Rect(x, y, width, height));

    //objectMetadataPacket->addItem(objectMetadata.get());

    return objectMetadataPacket;
}

There is one more question. Why I can't set my unique trackId as string to uuid in setTrackId? I can't get any result if I use it, but randomUuid is work.

        //auto track_id = nx::sdk::UuidHelper::fromStdString( std::to_string( this->object_list_[i].nObjectID ) );

        auto track_id = nx::sdk::UuidHelper::randomUuid();

        object_metadata->setTrackId( track_id );