On 02/13/2011 05:02 AM, Eric Benjamin wrote:
> I was recently perusing the Ambisonics 2010 Symposium web site and came 
> across 
> the pages devoted to a streaming concert.  The audio (4th order Ambisonics) 
> is 
> available as a downloadable Ogg Vorbis file:
> 
> http://ambisonics.iem.at/xchange/ambisonicssymposium_stream/concert-ambisonics-recording-ogg/at_download/file
> 
> 
> I downloaded the file and then spent most of the night trying to play it.  I 
> downloaded more than a dozen Ogg players and converters and almost all of 
> them 
> choked on the stream.  I did find two ways to decode the file, one of them 
> being 
> the latest version of Audacity and the other being an add-in filter file for 
> Cool Edit.  Both of these agree that the file has nine channels, but 6 of 
> them 
> are empty.  Not a satisfactory experience!  Either the decoders are broken or 
> the file is.
> 
> Have any of you been able to successfully decode this file?

i just ran it through oggdec, and i'm seeing the same: 9 channels, and
all but the first three are silence.

anyways, how can this file be "ambisonic"? it uses spherical
decomposition alright, but i doubt it could provide meaningful
information when played back over an inward-facing sphere of speakers.

iiuc, it's meant to be reproduced by either an outward-facing
higher-order point source such as an icosahedron, or via wfs (where you
would take a subset of the signals and only look at the frontal part of
the trombone sound, to be able to reproduce the frontal directivity of
the instrument).


-- 
Jörn Nettingsmeier
Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487

Meister für Veranstaltungstechnik (Bühne/Studio), Elektrofachkraft
Audio and event engineer - Ambisonic surround recordings

http://stackingdwarves.net

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