[FFmpeg-user] encode five wav files to one Dolby Prologic II encoded file

Martin Thomas Schrott list at mtsonline.at
Fri Mar 24 15:15:35 EET 2023

Hi Michael,

yes, it is not documented - wich caused me a headake for many days ;-)

After houndreds of tests I would say 1 = 180°

What is, what I also expekted to get a 360° spectrum from -1 to +1 :-)

And my tests also gave the best results with 0.5 and -0.5 values. :-)

as a shift of more than 180° in one direction would not make sense - 1 
should be the maximum and the half is 90°.

I think an example for how to encode dplii with ffmpeg should be added 
to the ffmpeg docs including the aresample=matrix_encoding and 
aphaseshift filters.

Aditionally it would be great if the matrix_encoding filter could be 
documented - nowhere can be found what this does exactly. After my tests 
I suppose it mixes the volumes following the dolby docs but does not 
shift the phases.



Am 24.03.2023 um 11:50 schrieb Michael Koch:
> Am 23.03.2023 um 13:45 schrieb Paul B Mahol:
>> Using aphase for phaseshift is certain not correct way to do it.
>> You need aphaseshift, with shift being 0.5  and -0.5.
> What's the unit of the "shift" option? Does shift=0.5 mean 90° or 180° 
> phase shift?
> That's unclear in the documentation.
> Michael
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