Infrared (IR) illuminators with a wavelength of 940 nm do not produce any visible glow. This wavelength is completely invisible to the human eye, making it ideal for covert surveillance applications where the presence of IR illumination needs to be undetectable. Other wavelengths like 650 nm, 750 nm, and 850 nm can produce a faint red glow that may be visible in low light conditions.

To achieve four H.264 streams at 30 fps from the same camera product that can deliver two full resolution 30 fps H.264 streams, the resolution of the streams must be decreased. By lowering the resolution, the camera reduces the amount of data processed and transmitted for each stream, making it possible to support additional streams. Axis Network Video documentation indicates that stream configuration, including resolution and frame rate adjustments, allows cameras to manage multiple streams effectively while maintaining performance.

Axis Official Documentation Extract:
"A video decoder is a device that receives video streams from IP cameras over the network, decodes the streams, and outputs the video to a monitor, typically using HDMI or other standard video outputs. This allows users to view live network video on standard monitors or televisions without the need for a computer."
- Source: AXIS Video Decoder Product Page
Supporting Extract from Axis Study Guide:
"Video decoders play a crucial role in network video systems where there is a need to display live video feeds on standard monitors. Unlike video encoders, which convert analog video to digital IP video streams, decoders convert IP video streams back into video signals that can be displayed on HDMI or composite video monitors."
- Axis Communications Academy, Network Video Fundamentals, 2022
References:
Axis Video Decoder Product Documentation
Axis Communications Academy, Network Video Fundamentals, 2022 (p. 35-36) Summary:A video decoder is the correct device to use when you need to display live network video on an HDMI monitor. It takes the network stream and converts it to a format compatible with the monitor's HDMI input, which neither a video encoder, recorder, nor a connectivity hub can do directly.

External (non-integrated) IR illumination can significantly enhance the performance of surveillance cameras in low-light conditions. By increasing contrast in the scene, it allows the camera to capture clearer images with more detail. Additionally, external IR illumination provides more flexibility in placement and coverage, ensuring that the entire area of interest is adequately illuminated. This can be particularly useful in large or irregularly shaped areas where integrated IR might not be sufficient. Axis documentation supports the use of external IR illuminators to improve image quality and scene visibility in low-light environments.

Axis P-iris technology is designed to optimize the iris position for optimal depth of field, resolution, and image contrast. It also helps in managing challenging lighting conditions such as backlighting by controlling the amount of light reaching the image sensor. This allows the camera to produce clear images even when facing direct sunlight or other bright light sources.