Main-stream and sub-stream concept was first developed by Hikvision. This technology has been used in Hikvision DVR to offer smooth video streaming for remote monitoring. Now it is widely used in DVR, NVR, IP camera across different manufacturers. This technology also called Dual-stream technology, it adopts one channel main-stream to deliver high definition video for local HD video recording/storage, such as 5 megapixel, 3 megapixel, 2 megapixel (1080p), 1.3 megapixel (720p), meanwhile one channel sub-stream to deliver low or standard definition video over Internet for remotely surveillance (e.g. viewing cameras on a smartphone). Dual-stream technology enabled video surveillance products deliver high definition video for local video storage, meanwhile overcomes 3G/ADSL network bandwidth limitation to deliver smooth low/standard definition video.