--On 27 January 2012 19:01 +0000 Paul Hodges <[email protected]>
wrote:
It could well be that the BBC made no change at all to their Matrix-H
encoding as a result of the publication of HJ. H fell within HJ (by
intent) and so continued to be acceptable.
I have (so far) found just one reference to HJ in the relevant BBC reports
that I know of. This is in BBC RD 1979/25: "Spherical harmonic analysis
and some applications to surround sound". This report discusses the M, S
and T components of a sound field (W, Y, X to us). It remarks that it is
not easy to convert from pair-wise panned signals to MST, but that both can
be fed to a System HJ (13LP2) encoder with satisfactory results. A diagram
shows on the HJ tolerance diagram the two loci for pairwise panned-potted
and hypercardioid signals, apparently defined by "option 13LP2 of HJ". It
then gives a detailed analytical account of the Soundfield microphone
(after remarking that the inventors had not).
Searching for 13LP2 and HJ together showed me just one paper, which I don't
have access to. The abstract is here: <http://is.gd/MU9ijH> (it's in the
IEEE library, if you don't like abbreviated URLs). The abstract says it
describes the hierarchical UHJ system, and then goes on: "The design and
development of the 424 System HJ is discussed in some detail, although this
paper necessarily only gives a brief account of the many facets of this
involved subject." It looks as if this might be a useful paper for those
interested in HJ to read.
Paul
--
Paul Hodges
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