Dave Hunt <davehuntau...@btinternet.com> wrote: > One of these complexities is presumably indicated by the phrase "Note > that two-channel UHJ requires the player to use different shelf > filters than for three- and four-channel UHJ (and B-Format)" at > http://en.wikipedia.org/wiki/Ambisonic_UHJ_format. > > Any clues as to why this should be so ?? If we get back something > close to three-channel B-Format, why should it be filtered > differently from a straight three-channel B-Format ?? The encoding/ > decoding has no frequency conscious components. Admittedly, the gains > of the filters may need to differ between 2D and 3D decoding.
See the thread on this mailing list from December 2008 with the Subject "decoding an UHJ-B stereo file to Ambisonics Quad". The thread included this post from Geoffrey Barton: <quote> Date: Tue Dec 30 12:16:42 EST 2008 Subject: [Sursound] decoding an UHJ-B stereo file to Ambisonics Quad Sorry to shatter your simple world, but the shelf filters do have to be different for 2 channel UHJ! As the BHJ-> 'WXY' decoding has magically produced three channels from two, there is information missing. This manifests itself as phase- shifts between the derived WXY signals. If you optimise the shelves to maximise rv at lf and ev at hf using these decoded signals, the resulting values are not the same as for b- format. You also have to watch the way MAG quoted these values as sometimes he quoted the 'kernel' values for b-format rather than the 'normal' b-format. Geoffrey </quote> Regards, Martin -- Martin J Leese E-mail: martin.leese stanfordalumni.org Web: http://members.tripod.com/martin_leese/ _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
