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SHAKE: mirrors, yaws, pitches and/or rolls the soundfield, but only in unit steps of 90 degrees, and only for first order files (see 'yaw', 'pitch', 'roll' for other angles/orders). The constraints make for a very fast/clean transformation. Giving a syntax for the 48 possible movements is though less easy/clean: -'flip' mirrors left to right and vice/versa (so the concert violinist will move from left stage to right stage). - 'flop' mirrors front to back (and vice/versa) (so the orchestra will move onto the back wall, but if you face the backwall, left and right will be inverted (it is a mirrored image afterall). ('flip+flop' will mirror to the backwall and mirror left to right, the same as rotating 180 degrees horizontally.). - 'flap' mirrors ceiling and floor. Any combination (upto once each) of 'flip+flap+flop' can be used. No whitespace and join the words with a '+' sign. - you can move the x-axis (the Front position) to any new coordinate '(a,e)', e.g. '(180,0)' is the same as 'flip+flop'. The brackets are obligatory and 0 <= a <= 360 with -90<= e <= 90 (standard polar coordinates (azimuth rotates anti-clockwise from 0 at Front to 90 at Left, etc.). Or you can Yaw or Pitch or Roll (but only one), using 'y|p|r 0|90|180|270' -but with no white space. 'y0' achieves nothing. 'y180' is equivalent to the previous examples (e.g. '(180,0)'). But, none of these shorthands will (easily?) describe the 48 possible placements. 'ULF' places the Upper sounds Up, the Left sounds to the left and the Front sounds to the Front(i.e. makes no change). 'URB' is equivalent to our repeated example. A table giving all 48 positions and their translation into the different notations is given on the Web. (Easy possible names for this command (roll, pitch) have special meanings. Die (singular of dice) was played with, but it also has another meaning (in Perl at least), 'shake' was (un)fortunately the next to come to mind ....) Usage "ambman --shake in.wav out.wav parameter" With examples of value for parameter being: "flip" "flip+flap" "flop+flap" "(270,-90)" "r180" "p90" "y270" "BDR"
Because this function includes mirroring options it can (unlike conventional yaw, pitch or roll conversions) produce an enantiomorphic soundfield (indeed 24 of the 48 options are such mirror images).
The non-technical explanation of the above is that if one were to
construct a die, one has two options of how to do so. Firstly (often
seemingly forgotten by artists!) 1 is always opposite 6, etc. (the two,
opposing faces always total 7). We are in the same situation: front
is always opposite back, etc. (That is not to say that skewing
soundfields is not possible, just that it is a totally different
If you make a die (following those rules) and then make its mirror image, the two will be different. One can never be rotated to become the other (absent quickly flipping it over in the fourth-dimension (not advised))
Apologies the digression.
October 2007, updated November 2007.
Copyright © 2007 Michael Chapman.