[sc-users] FMHEncode1/2 and ambdec

[Iain Mott <mott@xxxxxxxxxxxxxxx>]

Hello list,

Is it possible to use Fons Adriaensen's ambdec to decode FMHEncode1/2 
encoded 2nd order signals? If so, which of FMHEncode's two scaling modes 
correspond to one (or two) of the 'N3D', 'SN3D' and Furse-Malham 
scalings available in ambdec?

I'll paste below the paragraph on scaling in the ambdec manual

Thanks,

Iain


In order to correctly use some of the options discussed below, the 
following must be understood.
Ambisonic signals are traditionally scaled in a number of dierent ways.
For mathematical analysis it is very convenient to use the normalised 
form, meaning that each
spherical harmonic has unity power when integrated over the sphere. This 
is called the 'N3D'
form of Ambisonic signals. A close variation on this is the 
'semi-normalised' or 'SN3D' form. This also has desirable
mathematical properties, and is used by some existing software, for 
example the Ambisonic
tools from IEM, Graz. The alternative to both, and widely used, is the 
so-called Furse-Malham form. This applies some gain factors to the 
signals so that they all have the same maximum level over all 
directions. The
only exception is the pressure signal W which, for historical reasons, 
is attenuated by 3 dB.
Many Ambisonic applications and audio les use the Furse-Malham 
representation.
AmbDec allows to use all three representations, both for the input 
signals and for the matrix
coecients. If the two settings are dierent, AmbDec will automatically 
apply the necessary
gain factors to convert between them. So you can design a decoder matrix 
using the normalised
form (which is usually less confusing, in particular for higher orders), 
and then use it with signals
scaled according to the Furse-Malham standard. Important note: the 
normalised form used is always the 3-D one, even for an horizontal-only 
decoder. The reason for this is that all decoders are used in 3-D space 
| unless your speaker are innite vertical line sources the rules of 
physical 3-D space apply, even when analysing a 2-D
decoder.


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