It means a channel of video images passing through the video coder, and output multi- independent bit streams as shown in the figure:
The resolution, frame rate, bit rate and other parameters of output bit stream can be set independently. The output dual steam can meet different demands, for example, one for hard disk storage and the other for network transmission.
HD Surveillance :
5.0MP (2560x1920), 3.0MP(2048x1536), 2.0MP(1920x1080), 1.3MP (1280x720)
WD1 (960x675), D1 (704x576), CIF(352x288)