Dark Shikari (talk | contribs) slight corrections |
Timharwoodx (talk | contribs) reverting page because editor refuses to accept existance of obvious grammar errors an 8 year old child could see - lets try again. Can you reach the level of an 8 year old child? |
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'''Quarter pixel''' (often also called as q-pel or qpel) refers to a quarter of a standard [[pixel]]. It is an often-used term in video technology. |
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==Operation== |
==Operation== |
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Advanced video encoding methods such as those based upon [[MPEG-4]] specifications, for example [[XviD]], [[3ivx]], and [[DivX]], use [[motion estimation]] algorithms to significantly improve [[video compression]]. The default level of resolution for motion estimation for most [[MPEG-4]] implementations is half a pixel, although quarter pixel is specified under the standard. [[H.264/MPEG-4_AVC]] specifies quarter pixel as default. |
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==Implementations== |
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Gains in compressibility from more precisely describing intra-frame motion, are typically offset by the increased constant bitstream overhead of running a higher level of description. Therefore, enabling QPEL does not typically produce smaller file sizes. However, since QPEL delivers sharper images, an equivalent sized QPEL enabled file, will generally be perceived as offering higher visual quality, than a non QPEL file. To this extent, while QPEL files may not be smaller, they can be said to offer a higher level of visual detail compression. |
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[[Category:Video codecs]] |
[[Category:Video codecs]] |
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[[Category:Image processing]] |
[[Category:Image processing]] |
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[[de:Qpel]] |
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[[de:Quarter Pixel Motion Compensation]] |
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[[pl:Qpel]] |
[[pl:Qpel]] |
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Revision as of 18:04, 25 December 2007
Quarter pixel (often also called as q-pel or qpel) refers to a quarter of a standard pixel. It is an often-used term in video technology.
Operation
Advanced video encoding methods such as those based upon MPEG-4 specifications, for example XviD, 3ivx, and DivX, use motion estimation algorithms to significantly improve video compression. The default level of resolution for motion estimation for most MPEG-4 implementations is half a pixel, although quarter pixel is specified under the standard. H.264/MPEG-4_AVC specifies quarter pixel as default.
Implementations
Gains in compressibility from more precisely describing intra-frame motion, are typically offset by the increased constant bitstream overhead of running a higher level of description. Therefore, enabling QPEL does not typically produce smaller file sizes. However, since QPEL delivers sharper images, an equivalent sized QPEL enabled file, will generally be perceived as offering higher visual quality, than a non QPEL file. To this extent, while QPEL files may not be smaller, they can be said to offer a higher level of visual detail compression.
Hardware compatibility
QPEL requires up to twice as much processing power to encode, and 30-60% more processing power to decode. For this reason, and to enable wider hardware compatibility, QPEL is disabled in the default DIVX encoding profiles.