Sursound List Excerpts

From Ambisonia

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[edit] Audacity

As of May 1 2007, Richard Dobson has begun "poking at" Audacity and/or libsndfile in order to improve support for Ambisonics (B-Format) material.

Subject: 	
Re: [Sursound] Podium - for multichannel files?
	Sent By:
	sursound-bounces@music.vt.edu  On: Tuesday, May 01, 2007 6:35:19 AM
To: 	Surround Sound discussion group

I have now downloaded the sources. It uses libsndfile for file i/o, and
that has now been updated to recognise the .amb GUID.   Audacity is
unable to identify channels (after the intial "left" and 'right"), so  a
quad file just has "mono" idents for channels 3 and 4.

The real issue though is going to be in writing files. It looks like
changing it to write (generic) files in WAVE_EX format is in itself
simple (a different flag sent to libsndfile); but the source is mssing a
whole bunch of 3rd-party libraries, so it will be a while before I can
actually build it. Probably easier just to ask on the media-api list to
make the change. But getting it to write files in a specific m/c format
will be a different matter. That is where making changes (somehow) to
the libsndfile API will be needed, to accommodate new format
specifications.

This is the ongoing problem with inventing surround-sound file formats.
The inventing is (mostly) the easy part. The hard part is extending APIs
that hitherto have never had to specify more than the sample type,
number of channels and sample rate, and WAVE/AIFF file types, to define
a whole slew of more-or-less esoteric matrix or speaker-feed
configurations (where many are exclusive to one or other file type) -
without gratuitously breaking existing applications using that API! Any
API that has presumed that configurations only need to specify speaker
positions will be flummoxed by something like B-Format.


Richard Dobson



Bruce Wiggins wrote:
> crikey, I never knew Audacity would do that!  It even reads B-format
> wave files!
>  
> cheers
>  
> Bruce