On 09/15/2014 01:57 AM, Stefan Schreiber wrote:
The Ambisonics community might have to speed up certain developments if
you want to stay competitive.
- Whereas there are some (main) microphones for recording in Auro
8.0/9.0/10.0 format available, there doesn't seem to happen enough <
practical > work related to HOA microphones. The "4th order" Eigenmike
is on the market, but has some practical limitations concerning noise,
frequency range, aliasing etc.
There is no established standardized main microphone for Auro 3D. In
fact, practices vary wildly, so that different Auro 3D productions have
totally different degrees of localisation, crosstalk, and channel
decorrelation. This has dramatic effects on up- or downmixing
algorithms, if format conversions are required later in the production
chain.
One vocal proponent of Auro 3D as a classical recording format insists
that a huge square of omnis is the only acceptable miking technique. No
comment.
The format just defines speaker positions, not signal relationships.
Just today at IBC, I looked at Schoeps' "3D ORTF" prototype for Auro
ambience recording, which is a cube of supercardioids. It apparently
works well, but it's just one of many proposals, each with their
strengths and weaknesses.
It is easily possible to create a higher-order recording even without a
native HOA microphone, as long as it's understood that any ambient
microphones are used such that they do not contribute to any co-incident
holophonic image, but just add highly decorrelated diffuse field
information which is to some extent "artificial". In that sense, they
are not "ambisonic", they just use the Ambisonic format to include some
decorrelated ambience with sufficiently low crosstalk.
In practice, almost no recording stays single-point co-incident, except
for purist POA recordings under very controlled conditions, and only
when no "shaping" of the result is required or desired.
--
Jörn Nettingsmeier
Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487
Meister für Veranstaltungstechnik (Bühne/Studio)
Tonmeister VDT
http://stackingdwarves.net
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