[FFmpeg-user] Upmixing Dolby Pro Logic audio - still not possible?

Ted Park kumowoon1025 at gmail.com
Mon Apr 6 19:28:57 EEST 2020


> I see no mention of Dolby Pro Logic on that page, and according to this
> comment[1] that filter uses its own (necessarily heuristic) algorithm;
> it does not use the Pro Logic channel information embedded in the
> source.
> I'm interested in doing this in a "lossless" fashion, where the
> resulting multi-channel audio is identical to that produced by a
> Dolby Pro Logic-enabled AVR.

Do you mean the old DPL, or even DPLII, without the various enhancements Dolby put on it to extend patents?
If so I think all there is to it is doing the reverse operation for the matrixing applied to the channels (I don’t think there is any metadata if it’s not the IIz, IIx, etc variants.)

And the matrices have been reverse engineered pretty much to perfection so if you really don't want to get a reference decoder (which aren’t that expensive, though you might want an empty equipment rack handy) you could get the matrix coefficients by googling for them and do the math and get the separated channels by hand.

Ted Park

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