[FFmpeg-devel] [PATCH] [RFC] libavfilter HRTF/room acoustics filter [1/2]

Michael Niedermayer michael at niedermayer.cc
Mon Aug 8 22:59:51 EEST 2016

On Mon, Aug 08, 2016 at 06:27:44PM +0200, Carl Eugen Hoyos wrote:
> 2016-08-07 2:08 GMT+02:00 Michael Niedermayer <michael at niedermayer.cc>:
> >> On a somewhat related matter: I was browsing through the matrix encoder
> >> in libavresample/audio_mix_matrix.c, and possibly rediscovered the bug
> >> in https://trac.ffmpeg.org/ticket/4175 . Also, the 5-channel coefficient
> >> seems to disagrees with Dolby (see the notes I wrote at some point while
> >> editing the Wikipedia section in
> >> https://en.wikipedia.org/wiki/Talk:Dolby_Pro_Logic#Source_of_the_DPLII_encoding_matrix.3F).
> >
> > is this issue also affecting libswresample ?
> The fact that users have reported several times that our Dolby downmix is not
> correct / not perfect indicates that there is an issue affecting
> libswresample, no?

There are 2 things here.
first, some of the downmix requires a phase shift, there is no
implementation of that in either resampler.

the way i understood the mail here is that the coefficients themselfs
are wrong too, that should not really be in case of libswresample, but
of course a wrong reference might have been used or whatever

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Never trust a computer, one day, it may think you are the virus. -- Compn
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