Re: [LAU] placement.

Jorn, Thanks for the explanation.

I've found the wxyz wavs for a couple of fons's conf files, so i'm going to
try those. My brain smells like a burning battery at the moment, trying to
absorb enough ambisonics knowledge to be almost dangerous, and with the
experiments i'm conducting.

I tried the split IR, and you're right, it sounded awful. I'm just not smart
enough with this stuff yet.

Can't make LAC 2009, although i'd dearly like to turn up with a dictaphone,
and wheelbarrow full of parchment for note taking. Perhaps 2010 might be on
the cards though.

I'm having some success with more modest IRs, for position experimentation.
There's three in my little conf file, aand i've truncated 2 of them. Not
exactly scientific, but it's good for listening, and getting my head around
emulating, however crudely, an orchestral spacial model.

I'm doing this for stereo at the moment, but don't rule out a near future
multi channel recording model.

Not using firewire here, so that's ok.

I'm fond of pizza, with the very occasional sip of fine cognac.

Helps me think.

Honest.

Alex.

On Tue, Jan 20, 2009 at 8:34 PM, Jörn Nettingsmeier <
nettings@email-addr-hidden-hochschule.de> wrote:

> alex stone wrote:
> > I've done some crude experimenting and ask at this point, how do i
> > determine the format (i.e. short b-form ir or not) of a particular
> > IR? Is there a device or some sort of utility that i can use to do
> > this?
>
> to clarify things, there are no "short" or "long" IRs. what fons means
> is: the early reflections are the most characteristic aspect of a room,
> and they affect localisation the most. therefore, if you want to have
> ultra-realistic reverb, use an IR that was measured with the speaker
> where your intended instrument is and a soundfield microphone where the
> listening spot is. of course, in practice this is not done.
>
> so instead you use one reverb IR instead. it can be short (tail
> truncated) to save CPU, because the tail is decorrelated (blurred) and
> does not provide localisation cues, hence it would be wasteful to render
> it in b-format.
>
> the problem is: you will probably not get such a two-stage reverb
> calibrated unless you have a lot of experiences with both b-format and
> convolvers.
> if you can make it to lac2009, let's talk this through over pizza
> (that's how i learned my first steps in ambisonics from fons, and it
> works suprisingly well).
>
> an IR can only be in b-format if it contains 4 channels (WXYZ) for full
> 3D or 3 channels (WXY) for planar surround only.
>
> > The reason i ask is, i have a set of IR's for a hall, recorded 3
> > front stage, left middle right, and 3 back stage, left middle right.
> > I built a jconv .conf file with these IRs, and the result was near
> > 100% CPU, and a vertiable flood of Xruns. (AMD 64 Dual Core X2 5600+,
> > 64bit Ubstudio) I understand from this, i've used 'full' IRs, and
> > Jconv is attempting to process them all at once.
>
> probably, and the cpu usage goes up quickly the longer the IRs are.
> also, jconv has the nasty tendency to starve ffado hardware threads (not
> really jconv's fault, but needs some tuning), so if you are using a
> firewire interface, you might be in for some fun. it can be done though,
> works nicely for me, but it requires some poking.
>
> > So, I gather from what you've written, that there is either a
> > mechanism for creating short b-form IRs from a single IR wav, or i'll
> > have to find a specific IR that is recorded in such a way that i can
> > use portions, or sections of the IR, without taking such a
> > performance hit, or there is a mathematical means of extrapolating
> > sections from a single ir, already present in Jconv, and i'm not
> > 'getting it', at this point.
>
> as i said, i would recommend against attempting such a split reverb
> method, because very likely things will go haywire at some point.
> better bribe fons :)
>
> for now, i'd recommend to use one single reverb for all sources, and
> only vary the dry/wet ratio according to the distance to the virtual
> listening spot. should be really ok.
>
> what is your desired output format? plain old stereo, or 3d ambisonics?
>
>
>
>
>
>

_______________________________________________
Linux-audio-user mailing list
Linux-audio-user@email-addr-hidden
http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user
Received on Tue Jan 20 20:15:01 2009