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Video Compression & Transmission Terminology Glossary

Term Definition
Bandwidth Its popular meaning refers to the amount of data that can be transmitted per second over a wire or network.
When it comes to video surveillance applications you need a high amount of bandwidth to transmit the large files.
For remote viewing, 56K modems will not work well. DHL is OK, and cable modems or T1s (or better) are best.
And you also want the best video compression you can afford to make the files as small as possible.
CIF Common Intermediate Format – a set of resolution standards used in video applications, defined as follows:

  • CIF = 352 x 240 (‘Full CIF’ or just ‘CIF’)
  • QCIF = 176 x 120 (‘Quarter CIF’)
  • 4CIF = 704 x 480 (‘4 times CIF’)
CODEC
(aka “Code-Decode” or “Compression-Decompression”)
A term referring to any technology used to compress and decompress large files such as audio and video files for efficient data transfer.
Compression Standard
(or compression algorithm)
A standard approach or ‘formula’ for compressing (and decompressing) data (in our case, video and audio data).
There are many standard image or video compression algorithms available today (many are described below) and new ones come out each year.
D1 D1 is a video Resolution standard. In NTSC it is 720 x 480 pixels. Its affect on video compression and transmission is due to the fact that the excellent resolution of a D1 image produces larger files to be compressed and transferred.
H.264 Compression
(aka MPEG4+ or MPEG4-Part 10 or AVC (Advanced Video Coding))
The latest MPEG4 compression technology, released in 2003. H.264 provides excellent video compression. You get the same quality image as MPEG4 even at the higher resolutions like full screen D1.
ISO
(aka International Organization for Standardization)
ISO is an international organization founded in 1946 that organized and reviews standards worldwide. Their members such as ANSI (American National Standards Institute) and OSI (Open Systems Interconnection) create the standards and they review them for completeness and other criteria. ISO is not an acronym; the name derives from the greek word iso, which means equal.
Lossy Compression Sometimes a compression algorithm will lose some detail of the original image in its compression of that image. An algorithm that loses some detail of the original image is called a ‘lossy compression’ algoritm. JPEG, for example, is a ‘lossy’ compression.
NTSC National Television Standards Committee – the analog video representation standard used in the US and South America. Compare to PAL.
PAL Phase Alternating Line – the analog video representation standard used in Australia, and most of Europe and Asia. Compare to NTSC.
JPEG Compression
(aka Joint Photographic Experts Group)
A standard format for image compression (defined by the group who gave it its name) It was first introduced around 1986 and is a very common image format used on the web. JPEG is only used for photo (single frame) images (not video). JPEG is a ‘lossy’ image format – some of the detail of the image may be lost in its compression.
JPEG2000 Compression An update to the JPEG compression standard. Released in 2000, this standard offers both lossless and lossy compression and provides much better image quality at smaller filesizes than JPG does. File extension is “.jp2”.
MPEG Compression
(aka M-JPEG or “Moving Picture Experts Group”)
A standard format for video compression first introduced around 1988. MPEG achieves high compression rate by storing only the changes from one frame to another, instead of each entire frame. Although MPEG is lossy compression, the loss of image detail is generally imperceptible to the human eye except at the highest resolutions.MPEG has gone through several revisions as follows:

  • MPEG or MPEG-1 – The original MPEG, produces image quality similar to a conventional VCR
  • MPEG-2 – used in DVDs
  • MPEG-3 – there wasn’t one
  • MPEG-4 – combines MPEG-2 and Apple’s QuickTime technology (see below for more details)
MPEG4 Compression¬†(aka MPEG-4 or H.263) MPEG4 was standardized in 1998 by the ISO and combines MPEG-2 and Apple’s QuickTime technology. This resulted in a nice clear picture but also compressed much better than previous technologies.
MPEG4+ Compression (aka H.264) The latest MPEG4 video compression technology. See H.264 compression for more information.
Proprietary Compression Algorithm This refers to a compression algorithm that does not follow one of the compression standards such as MPEG4. Many times a proprietary algorithm will follow a standard mostly but then tweak it in some specific way. The result may be a better (more efficient or better quality) compression but the downside is that since it uses a proprietary formula it may not be compatible with other products. Many DVRs and IP systems will use a proprietary algorithm within their product (for example to store the images to the hard drive) but provide interfaces in standard formats to communicate with other systems (for example when backing up a particular video event to a DVD).
Resolution
(or Resolution Standard)
Resolution is a measurement of the quality or level of detail of an image. Usually expressed in terms of pixels, dots, or lines per inch. CIF and D1 are examples of some standard resolutions. The higher the resolution is, the greater the detail and number of pixels there will be in the image, and also the larger the recorded video file will be.
Run Length Encoding(RLE) This is a very simple form of data compression in which sequences of the same data value which occurs in many consecutive data elements are stored as a single data value and count, rather than as the original sequence.
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