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

[Paul B Mahol]

On 4/6/20, Ted Park <kumowoon1025 at gmail.com> wrote:
> Hi,
>
>> 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.


It is not that simple, it involves some complicated operations.

>
> Regards,
> Ted Park
>
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