From Hydrogenaudio Knowledgebase
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| Channel coupling is a method used to reduce [[bitrate]] demand by coding the stereo channel information more efficiently. there are several channel coupling methods. In mp3 the general term is [[joint stereo]].
| | #REDIRECT [[Joint stereo]] |
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| [[MP3]] can use 2 different channel coupling methods: mid/side-coding and [[intensity stereo]]. Mid/Side-coding calculates a "mid"-channel by addition of left and right channel (l+r)/2 and a "side"-channel (l-r)/2. With more mono-like signals one can use less [[bitrate]] to encode the side-channel, so that the overall bitrate will be less than encoding the left and right channel. [[intensity stereo]] destroys phase information, so it's used only at low [[bitrate|bitrates]].
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| Correctly implemented [[MP3]] mid/side stereo (like in [[LAME]]) does very little or no damage to the stereo-image and increases compression efficiency either by reducing size or increasing overall quality.
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| [[Ogg Vorbis]] and several lossless audio compressors can also use lossless channel coupling. In lossless channel coupling the channels will remain exactly the same as with stereo coding after the decoding.
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| [[Ogg Vorbis]] uses [[lossless]] channel coupling for high [[bitrate|bit rates]] only.
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Latest revision as of 05:22, 16 July 2023
