Some recording parameters may need motion to be supported by the camera. Motion + Lo-Res recording requires dual-streaming to be supported by the camera.
If dual-streaming is supported, the System tries to set second stream settings to low quality as follows:
•2 to 7 FPS
•320p to 480p (some cameras may set secondary stream resolution up to 720p). If the primary stream is 480p or less, it can be used for software motion detection as well.
Not only is the second stream used for recording, it is also used for motion detection and to save bandwidth and CPU during playback. See "Setting up Motion Mask and Motion Sensitivity" and "CPU and Bandwidth Saving during Playback".