AMBMAN shake

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Temporary documentation.

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 subject.)
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.


full notationflip/flop/flap polar YPR
ULF (0,0)
ULB flop
URF flip
URB flip+flop (180,0) y180
UFL
UFR (90,0) y90
UBL (270,0) y270
UBR
DLF flap
DLB flop+flap p180
DRF flip+flap r180
DRBflip+flop+flap
DFL
DFR
DBL
DBR
LUF
LUB
LDF r90
LDB
LFU
LFD
LBU
LBD
RUF r270
RUB
RDF
RDB
RFU
RFD
RBU
RBD
FUL (270,90)
FUR
FDL
FDR (90,0)
FLU
FLD (0,90)
FRU (180,90)
FRD p270
BUL
BUR (90,-90)
BDL (270,-90)
BDR
BLU (0,-90) p90
BLD
BRU
BRD (180,-90)

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Available (from release 0.5.3) via the main index page.

October 2007, updated November 2007.

Copyright © 2007 Michael Chapman.