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'''Data compression ratio''', also known as '''compression power''', is a [[computer science]] term used to quantify the reduction in data-representation size produced by a [[data compression|data compression algorithm]]. The data compression ratio is analogous to the physical [[compression ratio]] used to measure physical compression of substances.  
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==Definitions==
Data compression ratio is defined as the ratio between the ''uncompressed size'' and ''compressed size'':<ref name=CompressionRatioBroadcastEngineering>{{cite news |title=Pixel grids, bit rate and compression ratio |publisher=Broadcast Engineering |url=http://broadcastengineering.com/storage-amp-networking/pixel-grids-bit-rate-and-compression-ratio |date=2007-12-01 |accessdate=2013-06-05}}</ref><ref name=CompressionRatioDigitalVideoandHD>{{cite news |title=Digital Video and HD: Algorithms and Interfaces |edition=2nd |author=[[Charles Poynton]] |publisher=[[Morgan Kaufmann Publishers]] |isbn=9780123919267 |date=2012-02-07 |accessdate=2013-06-05}}</ref><ref name=CompressionRatioHEVCdraft10>{{cite news |title=High Efficiency Video Coding (HEVC) text specification draft 10 (for FDIS & Consent) |publisher=JCT-VC |url=http://phenix.it-sudparis.eu/jct/doc_end_user/current_document.php?id=7243 |date=2013-01-17 |accessdate=2013-06-05}}</ref><ref name=CompressionRatioLogitechAVCStandard>{{cite news |title=The H.264 Advanced Video Coding (AVC) Standard |publisher=Logitech |url=http://www.logitech.com/assets/45120/logitechh.pdf |format=PDF |accessdate=2013-06-05}}</ref><ref name=CompressionRatioSonyBroadcastApplications>{{cite news |title=White Paper on Performance Characteristics of MPEG-2 Long GoP vs AVC-I video compression techniques for Broadcast Applications |publisher=[[Sony]] |url=http://pro.sony.com/bbsccms/assets/files/micro/xdcam/solutions/MPEG-2_Long_GoP_vs_AVC_Comp-Strategies.pdf |format=PDF |accessdate=2013-06-05}}</ref>
 
:<math> {\rm Compression\;Ratio} = \frac{\rm Uncompressed\;Size}{\rm Compressed\;Size}</math>
 
Thus a representation that compresses a 10[[MegaByte|MB]] file to 2MB has a compression ratio of 10/2 = 5, often notated as an explicit ratio, 5:1 (read "five" to "one"), or as an implicit ratio, 5/1. Note that this formulation applies equally for compression, where the uncompressed size is that of the original; and for decompression, where the uncompressed size is that of the reproduction.  
 
Sometimes the '''space savings''' is given instead, which is defined as the reduction in size relative to the uncompressed size:
 
:<math>{\rm Space\;Savings} = 1 - \frac{\rm Compressed\;Size}{\rm Uncompressed\;Size}</math>
 
Thus a representation that compresses a 10MB file to 2MB would yield a space savings of 1 - 2/10 = 0.8, often notated as a percentage, 80%.
 
For signals of indefinite size, such as [[streaming audio]] and video, the compression ratio is defined in terms of uncompressed and compressed [[Bit rate|data rates]] instead of data sizes:
 
:<math> {\rm Compression\;Ratio} = \frac{\rm Uncompressed\;Data\;Rate}{\rm Compressed\;Data\;Rate}</math>
 
and instead of space savings, one speaks of '''data-rate savings''', which is defined as the data-rate reduction relative to the uncompressed data rate:
 
:<math>{\rm Data\;Rate\;Savings} = 1 - \frac{\rm Compressed\;Data\;Rate}{\rm Uncompressed\;Data\;Rate}</math>
 
For example, uncompressed songs in CD format have a data rate of 16 bits/channel x 2 channels x 44.1&nbsp;kHz ≅ 1.4 Mbit/s, whereas [[Advanced Audio Coding|AAC]] files on an iPod are typically compressed to 128 kbit/s, yielding a compression ratio of 10.9, for a data-rate savings of 0.91, or 91%.  
 
When the uncompressed data rate is known, the compression ratio can be inferred from the compressed data rate.
 
==Lossless vs. lossy==
[[Lossless compression]] of digitized data such as video, digitized film, and audio preserves all the information, but can rarely do much better than 2:1 compression because of the intrinsic [[information entropy|entropy]] of the data. In contrast, [[lossy compression]] (for example [[JPEG]], or [[MP3]]) can achieve much higher compression ratios at the cost of a decrease in quality, as visual or audio compression artifacts from loss of important information are introduced. A compression ratio of at least 50:1 is needed to get [[1080i]] video into a 20 Mbit/s [[MPEG transport stream]].<ref name=CompressionRatioBroadcastEngineering/>
 
==Uses==
The data compression ratio can serve as an measure of the [[complexity]] of a data set or signal, in particular it is used to approximate the [[algorithmic complexity]].
 
==References==
<references/>
 
==External links==
*[http://www.cartesianinc.com/Tech/tech-overview.html Nondegrading lossy compression]
 
[[Category:Data compression]]
[[Category:Engineering ratios]]

Latest revision as of 00:34, 9 March 2014



You see I run a toy shop online. Now while that gives me authority on subject of it also gets customers to think I'm pitching them gifts i want the particular buy. Less than! If my brother asked me which were the best gifts for Christmas, I'd say specific.

Alan Jones was MC and the warm-up included a video clip taking a gentle hearted the Clinton's last days in office. Scenes included Clinton washing the Presidential car, clipping the hedges and playing switchboard operator within the Oval Open area. A great scene from a press conference showed Clinton waking a single sleeping reporter.

If you've got a bright room, hang new, fully mature plants in the room. This will a number of circumstances impression how the room is perfect for growing beautiful bouquets. If you have some rooms which receive little sunlight, brighten them track of a light coloured coat of wallpaper. Finally, one of internet site ways to raise the appearance of any room is to simply raise the wattage among the lightbulbs - the room will not show better, it furthermore look much bigger.

When you consider landscaping, consider your water needs due to the local climate. These factors will help you that to plant. For example, if your area has water limitations or restrictions, then you need to choose low maintenance plants that require little water.

Let us discuss the important thing monetary costs associated with home buying to compare against your monthly rent check. You will notice points to take into account when opting for buying versus renting.

The petrol powered types are while being two-stroke or four-stroke models. With two-stroke models you want mix the fuel properly as it is not possible to purchase ready mixed fuel. You will be getting to buy both petrol and oil and make sure you mix the quantities to the very best ratio for your chosen brush cutter. The instructions for this should along with the brush cutter. Two-strokes have fewer moving parts and so there is less to go to wrong with them; thus, less secours.

We Actually take on calculated risk or the market will never pay us for our services. In addition, automobile has to relocate far enough to create a profit without letting legal action of protection eat us up. Excessive protection (risk avoidance) can come in is also important . of option premiums, too close-in stop-loss orders - and overdone, complex spread strategies. Matching a forecast to a method is a critical skill techniques in commodity trading.

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