Downmixing
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Downmixing is a general term used for manipulating audio where a number of distinct audio channels are mixed together to produce a lower number of channels. Also known as fold-down.
Sometimes, "Downmixing" is also used in radio communication to describe a process that brings an IF signal down to baseband via demodulation with a complex carrier frequency.
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[edit] Example
For example when converting 6 channel audio (for example 5.1 audio) to stereophonic sound (2 channels) the process is called downmixing. This example is a common feature of DVD players and Personal computer sound cards.
[edit] Stereo downmixes/(or fold-downs)
[edit] Left total/Right total (Lt/Rt)
Lt/Rt is a downmix suitable for decoding with a Dolby Pro Logic surround sound device.
Lt = L + -3dBC - -3dB(Ls + Rs)
Rt = R + -3dBC + -3dB(Ls + Rs)
(Ls,Rs 90-degree phase shifted)
[edit] Left only/Right only (Lo/Ro)
Lo/Ro is a downmix suitable for stereophonic sound playback on a hi-fi or on headphones.
Lo = L + -3dBC + attLs
Ro = R + -3dBC + attRs
(att=-3dB or -6dB or -9dB or 0)
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