Resolution

Digital network camera resolutions are based on a common global standard, that refers to pixels rather than TV lines.

The table below will guide you through some of the common resolution settings (in pixels) and how they correspond to different market standards. The earlier standards are from the analog world and are based on TV line resolutions.

Resolution	Pixels	Typical market	Comments
CIF	352 x 240	US , Japan	NTSC standard
CIF	352 x 288	Europe	PAL standard
4CIF	704 x 480	US , Japan	NTSC standard
4CIF	704 x 576	Europe	PAL standard

QVGA	320 x 240	Global	Digital standard
VGA	640 x 480	Global	Digital standard
XVGA	1024 x 768	Global	Digital standard
MegaPixel	1280 x 960	Global	Digital standard

Analog vs Digital technology (lines and pixels)

Interlaced scan
The "standard" NTSC system uses 525 scanning lines to create a picture. The picture is made up of two fields: The first field has 262.5 odd lines (1,3,5...) and the second field has 262.5 even lines (2,4,6...). The odd lines are scanned in 1/60th of a second, and the even lines follow in the next 1/60th of a second. This presents an entire frame of 525 lines in 1/30th of a second.

Progressive scan
Instead of splitting each video frame into two sequential fields like standard interlaced NTSC video, progressive-scan video displays the entire frame in a single sweep. Where standard NTSC video displays 30 frames, progressive scan displays 60 full frames per second.

Resolution
The sharpness of a video image is generally described either in terms of "lines of resolution," or pixels. The resolution you see depends on two factors: the resolution of your display and the resolution of the video signal. Video images are rectangle- shaped. There is both horizontal resolution and vertical resolution.

Vertical resolution: The number of lines (or pixels) that can be resolved from the top of an image to the bottom. The vertical resolution of the analog NTSC TV standard is 480 lines in the final image. All typical NTSC sources — VHS, cable and broadcast TV (analog), non-HD digital satellite TV, DVD players, camcorders, etc. — have vertical resolution of 480 lines.

Horizontal resolution: The number of lines (or pixels) that can be resolved from one side of an image to the other. Horizontal resolution is a trickier concept, because the horizontal resolution varies according to the source. Some examples for typical sources: VHS (240 lines), analog TV broadcasts (330 lines), non-HDTV digital satellite TV (up to 380 lines), and DVD players (540 lines).

Next topic