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Image Compression
Technology
VisionNet Network DVR compress video prior to record them into
"Storage Buffer". The compression purpose is to save space and
enhance network transmission. For instance, SW-80 compress each
frame into 2.5kb in size.
There are many Digital Compression Standard in
the field of computing. And many mores are still in research and
development. Until now, remarkably one include Motion JPEG, MPEG-1,
MPEG-2 and MPEG-4.
Motion JPEG:
With motion JPEG, each frame within the video is stored as a
complete image in the JPEG format. The still images are displayed at
a high frame rate to produce very high-quality video, but at the
cost of producing comparatively large file sizes.
Applications: Webcam, mobile......
MPEG-1:
Moving Picture Encoding Group international standard ISO/IEC 11172.
This standards produce "VCR quality", giving performance of up to
352x288 pixel, 30fps, max 1.86Mbit/s.
As the available resolution is quite limiting, and the size of video
is relatively large, one hour recording takes up to 650-700 MB.
Applications: VCD
MPEG-2:
Moving Picture Encoding Group international standard ISO/IEC 13818.
Most widely known standard for DVD, that offers high quality video
suitable for installations where TV-quality is needed. This standard
provide a resolution of 720x480 pixels at 30fps NTSC or 720x576,
25fps PAL. The bit rate is typically 1-10 Mbit/s. Although this
format is excellent for image quality, but the recording size takes
up to GB level.
Applications: DVD
MPEG-4:
Moving Picture Encoding Group international standard ISO/IEC 14496.
This standard covers a wide variety of applications ranging from the
video displayed in cellular phones, to full feature-length movies
shown in a cinema. MPEG 4 is widely used to be the video standard of
the future.
This format contains many enhancements to any of the early MPEG
standards: for example, it offers narrower bandwidth and can mix
video with text, graphics and 2-D and 3-D animation layers. High
performance hardware and sophisticated techniques are required to
produce MPEG-4 video, therefore, many security companies can't adopt
this format in their products. In fact, this format provide image
quality comparable to MPEG2, depending on frame rate and resolution,
the recording size is excellent for security surveillance recording.
One hour of video with 25fps takes 150-200MB.
Applications: VisionNet Network DVR, digital movie......
For more
information:
Video Camera Selection Guide - White Paper | 
