> > > Message: 5 > Date: Sat, 15 Jan 2011 19:44:05 +0100 > From: f...@kokkinizita.net > Subject: Re: [Sursound] Available UHJ encoders? > To: Surround Sound discussion group <sursound@music.vt.edu> > Message-ID: <20110115184405.GA4117@zita2> > Content-Type: text/plain; charset=us-ascii > > On Sat, Jan 15, 2011 at 06:19:33PM +0000, d...@york.ac.uk wrote: > >> problem with Fon's code is that the filter poles are pre-optimised >> for a limited range of sample rates (44.1/88.2 and 48/96) and I'd >> like more even more choice. > > 192 kHz ??? > >> It shows a little bit more phase >> difference variance at the higher frequencies than the CSound >> implementation but unless I am missing something it is only a four >> pole per leg implementation, as opposed to CSounds (and Geoffrey's) >> 6 poles per leg. > > Yes, 2 second order sections in series. > >> In both cases, however, the low end (under a >> hundred Hz) becomes problematic at the higher sampling rates, > > Are you sure ? > > I measure +/- 4 degrees error in the range 20Hz .. 20kHz, even > at 96 kHz. Below 20Hz it gets worse of course.
UHJ needs all the help it can get, and the analogue design Dave referred to is 6 pole/zeroes in each of the 0 and 90 degree sections, designed for a phase ripple of <1degree 20~20k. Too much ripple gives blurring and mis-location in the images. IMHO 4 degrees is way too much. rgds, Geoffrey _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
