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

[Paul B Mahol]

On Thu, Mar 23, 2023 at 11:14 AM Martin Thomas Schrott <list at mtsonline.at>
wrote:

> Hi,
>
>
> if anyone needs it - here is the sample extended with manual phaseshift:
>
> https://forum.doom9.org/showthread.php?t=184793
>
>
> best wishes
>
> Martin
>
>
> Am 14.03.2023 um 15:09 schrieb Martin Thomas Schrott:
> > Hi guys,
> >
> >
> > okay I realiced how to get five separate wav files into one stream:
> >
> > ffmpeg -i $fl -i $fr -i $fc -i ${bl}_shift.wav -i ${br}_shift.wav
> > -filter_complex "[0:0][1:0][2:0][3:0][4:0]amerge=inputs=5,
> > aresample=matrix_encoding=dplii" out.wav
> >
> >
> > but I am still not getting correct dplii encoded channels.
> >
> >
> > Anyone an idea what I am doing wrong?
> >
> >
> > * how would I do the phaseshift correctly?
> >
> > * does matrix_encoding=dplii do the mixing or do I have to add another
> > command ... what does matrix_encoding=dplii do exactly?
> >
> >
> > thanks for any help
> >
> > Martin
> >
> >
> >
> > Am 05.03.2023 um 20:18 schrieb Martin Thomas Schrott:
> >> Hey Guys,
> >>
> >>
> >> after days of reading documentary, searching the net and all lists,
> >> trying and loosing, I hope someone here can help me to succeed.
> >>
> >>
> >> I read, some say ffmpeg is not capable of encoding, others say ffmpeg
> >> can do it. Some say it misses the phaseshift of the surround
> >> channels, others and the docu tell, it can.
> >>
> >> So after all I found, I would guess ffmpeg should be able to take
> >> five wav files as input and output one wav file in stereo, that is
> >> correctly dolby Prologic II encoded including the phaseshifts. But I
> >> cannot find how this has to be done to work correctly and there is
> >> not a single example anywhere to be found.
> >>
> >>
> >> I tryed countless ways so I post one of them and hope you can guide
> >> me where to go or what to change to be successful. :-)
> >>
> >>
> >> This one is with manual phaseshift of the default 0.0 that should be
> >> 90 degrees for the two back channels, as nowhere is stated if the
> >> matrix_encoding does apply this automatically.
> >>
> >> /Applications/ffmpeg -y -i bl.wav -af aphaseshift bl_phaseshift.wav
> >>
> >> /Applications/ffmpeg -y -i br.wav -af aphaseshift br_phaseshift.wav
> >>
> >>
> >>
> >> /Applications/ffmpeg -y -i fl.wav -i fc.wav -i fr.wav -i
> >> bl_phaseshift.wav -i br_phaseshift.wav -map 0 -map 1 -map 2 -map 3
> >> -map 4 -af aresample=matrix_encoding=dplii surround.wav
> >>
> >>
> >> it gives an error, that a wav file exactly expects one stream. I
> >> thought the matrix_encoding would output the five wav files in one
> >> stereo stream?
> >>
> >> If I change to .aac as output I would get a file, but this would not
> >> be a correctly encoded Dolby Prologic II file. This would have
> >> distroyed back channels.
> >>
> >> Same if I do not apply the phaseshift manually.
> >>
> >>
> >> So I am doing something wrong - anybody here who can help me to find
> >> the correct commands?
> >>
> >> Would be so thankful. I also did not find a working solution without
> >> ffmpeg, so if someone has an alternative this also would be okay -
> >> even I would prefer the ffmpeg way :-)
>

Using aphase for phaseshift is certain not correct way to do it.

You need aphaseshift, with shift being 0.5  and -0.5.


> >>
> >>
> >>
> >> best wishes,
> >>
> >> Martin
> >>
> >>
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> >>
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