Transcript Video Recording Systems

VIDEO SYSTEMS
University of Pitesti
Dolnośląska Wyższa Szkoła Przedsiębiorczości i Techniki w
Polkowicach
Dobrica Adrian
Dr inż. ZDZISŁAW PÓLKOWSKI
Polkowice, 2015
TOPICS MENU
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Definition
General information
Characteristics of video streams
Video format
Transport medium
Overview of a network video system
Definition
• Video is an electronic medium for the recording, copying,
playback,broadcasting,and display of moving visual and audio media
• Video
technology
was
first
developed
for
cathode
ray
tube (CRT) television systems, but several new technologies for
video display devices have since been invented. Charles Ginsburg led
an Ampex research team developing one of the first practical video tape
recorder (VTR). In 1951 the first video tape recorder captured live images
from television cameras by converting the camera's electrical impulses and
saving the information onto magnetic video tape.
http://en.wikipedia.org/wiki/Video
Video Recording Systems
• The IP recording and management system is a key part of
your IP camera system. If you select the wrong system, you
could find yourself without the key video evidence you need
when an incident occurs, or worse still your security could be
breached and safety threatened because of the wrong
choice.
http://www.kintronics.com/video-recording-systems/
Block diagram
http://www.kintronics.com/video-recording-systems/
• Video Management Software (VMS) is software only
that runs on your Windows computer and can be scaled
to any size of system.
• Network Video Recorder (NVR) is a complete system
that includes the computer and software and is typically
proprietary and not expandable.
• Cloud service provides remote recording (over the
Internet) for IP cameras at many different locations.
http://www.kintronics.com/video-recording-systems/
Overview of a network video system
• Network video, often also called IP-based video surveillance or IPSurveillance as it is applied in the security industry, uses a wired or wireless
IP network as the backbone for transporting digital video, audio and other
data. When Power over Ethernet (PoE) technology is applied, the network
can also be used to carry power to network video products.
• A network video system allows video to be monitored and recorded from
anywhere on the network, whether it is, for instance, on a local area network
(LAN) or a wide area network (WAN) such as the Internet.
http://www.axis.com/products/video/about_networkvideo/network_video.htm
General information
Persistence of vision:
The eye (or the brain rather) can retain the sensation of an image for a short
time even after the actual image is removed.
1. Frame merging
• This allows the display of a video as successive frames as long as the frame
interval is shorter than the persistence period, The eye will see a
continuously varying image in time.
• Higher frame rate is required with closer viewing and brighter display.
-For TV viewing: 50- 60 fps
-For Movie viewing: 24 fps
-For computer monitor: > 70 fps
2.Line merging
• As with frame merging, the eye can fuse separate lines into one complete
frame, as long as the spacing between lines is sufficiently small.
• The maximum vertical spacing between lines depends on the viewing
distance, the screen size, and the display brightness.
http://electronicaupit.com/forum/index.php?board=4.0
General information
3.Merging pixels
• Similarly, the eye can fuse separate pixels in a line into one continuously
varying line, as long as the spacing between pixels is sufficiently small.
4.Interlacing
• For some reason, the brighter the still image presented to the viewer ... the
shorter the persistence of vision.
• If the space between pictures is longer than the period of persistence of
vision then the image flickers. Therefore, to arrange for two "flashes" per
frame,
• interlacing creates the flashes. The basic idea here is that a single frame is
scanned twice. The first scan includes only the odd lines, the next scan
includes only the even lines.
http://electronicaupit.com/forum/index.php?board=4.0
Characteristics of video streams
• Aspect ratio describes the dimensions of video screens and
video picture elements. All popular video formats are rectilinear,
and so can be described by a ratio between width and height.
The screen aspect ratio of a traditional television screen is 4:3,
or about 1.33:1. High definition televisions use an aspect ratio
of 16:9, or about 1.78:1. The aspect ratio of a full 35 mm film
frame with soundtrack (also known as the Academy ratio) is
1.375:1.
http://electronicaupit.com/forum/index.php?board=4.0
Characteristics of video streams
• Color model name describes the video color representation. YIQ was used
in NTSC television. It corresponds closely to the YUV scheme used in NTSC
and PAL television and the YDbDr scheme used by SECAM television.
• The number of distinct colors a pixel can represent depends on the number
of bits per pixel (bpp). A common way to reduce the amount of data required
in digital video is by chroma subsampling(e.g., 4:4:4, 4:2:2, 4:2:0/4:1:1).
Because the human eye is less sensitive to details in color than brightness,
the luminance data for all pixels is maintained, while the chrominance data is
averaged for a number of pixels in a block and that same value is used for
all of them. For example, this results in a 50% reduction in chrominance data
using 2 pixel blocks (4:2:2) or 75% using 4 pixel blocks(4:2:0). This process
does not reduce the number of possible color values that can be displayed, it
reduces the number of distinct points at which the color changes.
http://electronicaupit.com/forum/index.php?board=4.0
Characteristics of video streams
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Video quality can be measured with formal metrics like PSNR or
with subjective video quality using expert observation.
The subjective video quality of a video processing system is evaluated as
follows:
Choose the video sequences (the SRC) to use for testing.
Choose the settings of the system to evaluate (the HRC).
Choose a test method for how to present video sequences to experts and to
collect their ratings.
Invite a sufficient number of experts, preferably not fewer than 15.
Carry out testing.
Calculate the average marks for each HRC based on the experts' ratings.
http://en.wikipedia.org/wiki/Video
Video format
• Analog video is a video signal transferred by an analog signal. An
analog color video signal contains luminance, brightness (Y)
and chrominance (C) of an analog television image. When combined
into one channel, it is called composite video as is the case, among
others with NTSC, PAL and SECAM.
• Analog video may be carried in separate channels, as in two
channel S-Video (YC) and multi-channel component video formats.
• Analog video is used in both consumer and professional television
production applications. However, digital video signal formats with
higher quality have been adopted, includingserial digital
interface (SDI), Digital Visual Interface (DVI), High-Definition
Multimedia Interface (HDMI) and DisplayPort Interface.
http://en.wikipedia.org/wiki/Video
Transport medium
• Video can be transmitted or transported in a variety of ways.
Wireless broadcast as an analog or digital signal. Coaxial cable
in a closed circuit system can be sent as analog interlaced 1
volt peak to peak with a maximum horizontal line resolution up
to 480. Broadcast or studio cameras use a single or dual
coaxial cable system using a progressive scan format known as
SDI serial digital interface and HD-SDI for High Definition video.
http://en.wikipedia.org/wiki/Video