Network Video Surveillance Technologies
The chain from photons to packets
Understand the signal path: lens and sensor, image processing (exposure, white balance, noise reduction), compression, then network transport. Questions often test where a given artifact originates, so map symptoms to stages: motion blur is an exposure/shutter issue, blocking is compression, and tearing is usually a client or decoder issue rather than the camera.
Compression and codecs
Know the difference between intra-only codecs (Motion JPEG) and inter-frame codecs (H.264, H.265). Inter-frame codecs send I-frames plus predicted P/B frames, giving lower bitrate at the cost of latency and error propagation. H.265 roughly halves bitrate versus H.264 at similar quality. Zipstream-style smart streaming reduces bitrate by dropping detail in irrelevant areas while preserving forensic regions. Trap: candidates assume lower bitrate always means lower quality; the right answer usually depends on scene content and motion.
Light, sensors, and low-light behavior
Distinguish sensitivity (sensor and lens speed), noise, and frame rate. WDR handles scenes with both bright and dark areas by combining exposures; it is not the same as simple brightness gain. IR illumination is monochrome and has range limits. Thermal cameras detect emitted heat and are unaffected by visible-light conditions but have lower resolution.
Network fundamentals
Know PoE classes and budgets, VLANs, multicast versus unicast, and the effect of packet loss on video. RTSP carries streams; ONVIF provides interoperability profiles. Trap: confusing bandwidth with storage - bitrate drives both, but retention math must include frame rate and recording schedule.
Rule of thumb
Estimate storage as bitrate (Mbps) x 3600 x hours / 8 = MB per camera per period. A 4 Mbps stream for 24 hours is about 43 GB before overhead - always add margin for motion spikes.