This term is typically used to indicate a device capable of providing two different application or compressions.
The dual steam can meet different demands one for hard disk storage and the other for network transmission. Parameters of stream output can be set independently like resolution, frame rate, bit rate, quality and others. or
DVR that can display live video in H.264 and transmits in M-JPEG compression. This may be sometimes referred as Dual Codec / Dual streaming. Our network products like 11series / 21 series / Professional IP series as can work real time even in network. Refer the images given below.