extract mid side channel audio
Mid is (L+R)/2 and Side is (L-R)/2: this tool's Mid mode outputs a result numerically identical to its Average mode, it is the same formula under a different name. The practical difference sits in Side, which drops to zero when both channels are identical and preserves full amplitude when they are completely out of phase, exactly the content that vanishes when summing to mono.
All the content is shared between both channels, so there is nothing left for Side to represent.
This is the riskiest scenario for anyone summing to mono without checking first: the channel that looked like it had content disappears completely.
The highlighted region isolates exactly the problem section, instead of letting it hide inside a favorable average.
Averaging sums L and R and halves the result, which preserves centred content (vocals, kick) but can cancel anything recorded in opposite phase. The L and R modes simply discard one channel: you lose whatever only existed on the other side, but you gain a guarantee that nothing will cancel. When the correlation strip shows negative stretches, that is exactly the trade-off to weigh.
Yes, numerically identical: both compute (L+R)/2 sample by sample. Mid is the name used when the focus is Mid-Side encoding (Mid plus Side), Average is the name used when the focus is just collapsing to one channel, but the exported result is the same file.
Because Side is the difference (L-R)/2, and when both channels are nearly identical that difference approaches zero. A centered voiceover or a mono-compatible studio recording has correlation near +1, so the Side channel of those tracks is naturally low, that is not a defect in the file.
Look at the compatibility verdict instead of trusting a single average correlation number: it merges contiguous windows below -0.1 correlation into highlighted regions, so a 15-second problem hidden inside a 5-minute track shows up isolated, even when the whole-file average would look safe.
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