In network video surveillance,the analog audio&video signals are imaging, capturing and encoding to digital audio&video signal to transfer on network is commonly called "stream".

Dual stream, that means it has 2 kinds of stream and enables you to take advantage of two different streams from an IP camera, NVR or DVR. One stream can be high definition video for recording, while the other stream can be a lower resolution for live display. (We need to view cctv on Mobile phone. If internet is slow, sub stream video will play smoothly & if internet is fast main stream video will be HD quality.)