Re: [Cs-dev] [Csnd] bformdec 8-ring

Date	2007-07-13 22:37
From	"Art Hunkins"
Subject	Re: [Cs-dev] [Csnd] bformdec 8-ring
	So let's see if I understand correctly (talking about ambisonics in Csound): 1) Zero degrees for all speaker arrangements is east (to the right). 2) 90 degrees is north (straight ahead) for all speaker arrangements. 3) Increasing degrees results in counterclockwise motion; decreasing, in clockwise motion. 4) Your recommendation for stereo is to mix the 8-ring format thus: outo a3 + a4 + a5 + a6, a1 + a2 + a7 + a8. (a3 through a6 are the Left side channels, the remainder the right side channels. This seems to give a good result for me. (I tried also: outo a1 + a2 + a3 + a4, a5 + a6 + a7 + a8 - which did not work.) Art Hunkins ----- Original Message ----- From: "Victor Lazzarini" To: "Art Hunkins" ; "Developer discussions" ; Cc: Sent: Friday, July 13, 2007 2:19 AM Subject: Re: [Cs-dev] [Csnd] bformdec 8-ring > yes, now we are back to my original comment, > stereo is problematic. The way I do stereo is > to use the 8-channel ring and mix the left annd > right hand signals down into L-R. That seems to > be the most satisfactory. > > Another thing you can do is binaural. Place the > 8 speaker signals through the HRTF, using the > known positions and then mixdown the 8 stereo > signals. I heard Jean Jacob Hoffman is doing this, > perhaps you can look in his site for suggestions. > > Victor > > > > > Victor, > > > > I think I'm pretty much with you now, and can verify both > > your 8-ring configuration and a comparable 4-ring (quad). > > > > What doesn't now seem to correspond, however, is stereo. > > The doc specifies speaker placement at 330 degrees and 30 > > degrees. Following the logic that 0 degrees is east, this > > gives placement appoximately at mid back right (330) and > > mid front right (30). In terms of stereo field it covers > > the east quadrant rather than the desired north. My tests > > seem to verify this. > > > > Obviously the problem arises because coverage of the > > soundspace is not symmetrical. What do we do about this? > > > > Art Hunkins > > > > ----- Original Message ----- > > From: "Victor Lazzarini" > > To: "Art Hunkins" ; "Developer > > discussions" > > Cc: > > Sent: Thursday, July 12, 2007 5:43 PM > > Subject: Re: [Cs-dev] [Csnd] bformdec 8-ring > > > > > > > > > > > I observe two issues: > > > > 1) Your zero-degree point is 90 degrees to the > > > > listener's right. The documentation implies that zero > > > > is immediately in front of the listener (this is also > > > > intuitive). 2) The documentation implies clockwise > > > > movement (as degrees increase), not counterclockwise > > > > movement. This clockwise movement implies > > > > channel/speaker numbers increasing with clockwise > > movement. > > > > That's right, the documentation is problematic. 0 > > > degrees is right (east), 90 is front (north), 180 left > > > (west) and 270 back (south). This is not so > > > counter-intuitive, as it just a trigonometric circle. > > > > > > > > > > > Would you agree that your speaker setup, reinterpreted > > > > in light of the above, is the equivalent of the > > > > following stereo pairs (front to back) - rotated 90 > > > > degrees counterclockwise (to put zero straight ahead) > > > > and with numbering reversed (so as to rotate > > > > clockwise): (8,1) (7,2) (6,3) (5,4) or outc a8, a1, a7 > > > > , a2, a6, a3, a5, a4 (with respect to bformdec > > outputs) > > > > I am not sure I follow it. The speaker setup is as I > > > gave in my e-mail and that is what should be figured in > > > the manual page. Angles are not clockwise. It's just > > > easy to apply the numbering I gave. The numbering I gave > > > is for stereo pairs (L, R) front to back. The one you > > > listed does not work. Front is 3,2 (not 8,1) etc.; so > > > you will have: > > > > > > a1,a2,a3,a4,a5,a6,a7,a8 bformdec ... > > > outq a3,a2,a4,a1,a5,a8,a6,a7 > > > > > > if you have the following speaker/channels from the > > > front: > > > 1 2 > > > 3 4 > > > > > > 5 6 > > > > > > 7 8 > > > > > > > > > > > > > > Furthermore, I assume that applying all the same > > > > reasoning to quad, but with the usual quad numbering > > > > (channels) for outq (LF = 1, LR = 2, etc.): outq a4, > > > > a3, a1, a2 (With this setup, quad ambisonics seems to > > work for me.) > > > > I have not tested quad, so I can't tell. I suggest it > > > would be RF,LF,LB,RB (counterclockwise starting from > > RF). > > > > > > > > > Somehow, I should think we need to get csound's > > > > ambisonic audio output into a format that is readily > > > > understandable by all. To my mind, the out statement > > > > is the place to do this. > > > > > > I hope this is clearer. > > > > > > > > > > > Art Hunkins > > > > > > > > ----- Original Message ----- > > > > From: "Victor Lazzarini" > > > > To: "Developer discussions" > > > > ; > > > > ; "Art Hunkins" > > > > Sent: Thursday, July 12, 2007 1:47 > > > > PM Subject: Re: [Csnd] [Cs-dev] bformdec 8-ring > > > > > > > > > > > > > Ok, we'll leave the angles out. Say your speaker > > > > > set up for a ring is: > > > > > > > > > > 1. mid front right > > > > > 2. front right > > > > > 3. front left > > > > > 4. mid front left > > > > > 5. mid back left > > > > > 6. back left > > > > > 7. back right > > > > > 8. mid back right > > > > > > > > > > Then you can plugin bformat outs 1-8 straight into > > > > 1-8. > > > > > > If you are working pair-wise L-R from the front, > > > > > then your pairs will be bformat outputs (3,2) (4,1) > > > > > (5,8) and (6,7). > > > > > > > > > > I hope this clears it up. > > > > > > > > > > Victor > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > I am very confused, and it may well be at least > > > > > > partly on the conceptual level. > > > > > > > > > > > > I'm trying to understand the bformdec > > > > > > documentation. It describes speaker placement, for > > > > > > quad, as starting at right front and running > > > > > > clockwise to left front. It also references > > > > > > degrees (on a unit circle), with straight ahead > > > > > > being zero degrees and degrees moving clockwise > > > > > > through 360. I think I understand this so far. (No > > > > > > reference is made to angles; since I am > > > > > math-challenged, I would like to leave them out of > > > > > > the discussion.) > If one is dealing with quad > > > > > > output from bformdec: a1, a2, a3, a4 bformdec > > > > > > > > > > > > the output options seem to be: > > > > > > 1) outq a1, a2, a3, a4 > > > > > > requiring verbal explanation of what this actually > > > > > > means in terms of speaker placement (as in > > > > > > "channel 1 is RF, channel 2 is RR" etc.; or > > > > > > > > > > > > 2) outq a4, a3, a1, a2 > > > > > > reinterpreting bformdec's output in terms of > > > > > > normal quad speaker/channel terminology - which > > > > > > (if I understand correctly) is LF = 1, LR = 2, RF > > > > > = 3, RR = 4. > > > > > > > I've less idea what such a reinterpretation might > > > > > > be for 8-channel circular mode. I've made the > > > > > > assumption (which certainly needs explanation to > > > > > > the "user") that the (normal?) counting of > > > > > > channels procedes in stereo pairs from front to > > > > > > rear. Assuming this, the output line would read: > > > > > 2) outo a8, a1, a7, a2, a6, a3, a5, a4 > > > > > > > I'd much appreciate being shown the error of my > > > > > > assumptions and thinking. There's either something > > > > > > wrong with my thinking, or with bformdoc, because > > > > > > - as I mentioned before - I'm not getting expected > > > > > > results with either quad or 8-channel bformdec. > > > > > > Using my test file, there is no speaker > > > > > > arrangement in which get a clear circular movement > > > > > > through 360 degrees. The placement is simply wrong > > > > > > , particularly in the range from 90 - 270 degrees. > > > > > > (I'm depending principally on strong aural and > > > > > visual LED evidence in a quad setting.) > > > > > > > Victor is happy; I'm not. > > > > > > > > > > > > And I'd still like to try out john ff's proposed > > > > > > bformdec, if there's any way to do so. > > > > > > > > > > > > Art Hunkins > > > > > > > > > > > > ----- Original Message ----- > > > > > > From: "Victor Lazzarini" > > > > > > To: "Developer > > > > > > discussions" > > > > > > Sent: Thursday, July 12, 2007 10:10 AM Subject: > > > > > [Cs-dev] bformdec 8-ring > > > > > > > > > > > > > > Dear all, > > > > > > > > > > > > > > I just ran the bformdec using the 8-ring setup > > > > > > > in the studio and as I said before here it works > > > > > > > as expected. The speaker positions are as > > > > > > follows: > > > > > > > > bformdec out speaker pos > > > > > > > (degrees) 1 22.5 > > > > > > > 2 67.5 > > > > > > > 3 112.5 > > > > > > > 4 157.5 > > > > > > > 5 202.5 > > > > > > > 6 247.5 > > > > > > > 7 292.5 > > > > > > > 8 337.5 > > > > > > > > > > > > > > Angles are measured counterclockwise from the > > > > > > > right, so right -> 0, front ->90, left ->180 > > > > > > and back 270. > > > > > > > > Victor > > > > > > > Victor Lazzarini > > > > > > > Music Technology Laboratory > > > > > > > Music Department > > > > > > > National University of Ireland, Maynooth > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > ---------------------------------------------------------- > > > > --------------- This SF.net email is sponsored by DB2 > > > > > > > Express Download DB2 Express C - the FREE > > version of DB2 express and take control of your XML. No > > > > > > > limits. Just data. Click to get it now. > > > > > > > http://sourceforge.net/powerbar/db2/ > > > > > > > _______________________________________________ > > > > > > > Csound-devel mailing list > > > > > > > Csound-devel@lists.sourceforge.net > > > > > > > > > > > > > > > > > > > > > > > > https://lists.sourceforge.net/lists/listinfo/csound-devel > > > > > > -- Send bugs reports to this list. > > > > > > To unsubscribe, send email to > > > > > > csound-unsubscribe@lists.bath.ac.uk > > > > > > > > > > > > > > > > > > ---------------------------------------------------------- > > > > --------------- This SF.net email is sponsored by DB2 > > > > Express Download DB2 Express C - the FREE version of > > > > DB2 express and take control of your XML. No limits. > > > > Just data. 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