Subject: Re: [linux-audio-user] Audio 3-D Demo --- Any Interest in Software?
From: Jan Depner (eviltwin69_AT_cableone.net)
Date: Tue Jan 06 2004 - 00:34:13 EET
Ron is dead-set against this becoming part of JAMin (which I tend to
agree with just because of the overhead). I was thinking of it in terms
of a polishing application. When I was reading up on mastering (trying
to get a handle on it) one of the things that caught my eye was a
suggestion to use an overall reverb on the stereo master to try to
provide a sense of "one room", what I was calling cohesiveness, for all
of the instruments. It seems that this may be a good way to do that, or
am I way off base here?
Jan
On Mon, 2004-01-05 at 15:49, davidrclark_AT_earthlink.net wrote:
> Thanks very much to those on the user list who listened to the demo
> and/or responded regarding 3-D Audio. I really appreciate all of the
> feedback. I'll try to answer some of the queries and comment on
> responses in one combined email rather than have a string of
> individual responses, so this is a little long. However, many of the
> themes are related, so I'd prefer to answer in this all-in-one manner.
>
> On "harshness" (Mark Constable) and "extreme" separation (Jörn) plus
> Mark's observations of the demo clips:
>
> Both the harshness and the extreme separation are adjustable. These
> effects people noticed aren't a necessary result of the 3-D processing
> by any means. The separation is exaggerated for this demo. The
> monophonic clip was included simply to emphasize that I did not merely
> take the reverberated, stereophonic output of the synth (clips #2 and
> #4) and "improve" it a little; instead I completely started over with
> very dull, dry, monophonic recordings (#1 and #5).
>
>
> Cohesiveness (Jan), preprocessing and bus-oriented reverbs (Mark
> Knecht):
>
> The 3-D processing provides a more well-integrated or cohesive sound
> due to the physical basis of the processing. In using typical DSP-
> oriented techniques, you are essentially processing the audio in a
> non-physical manner, despite the terminology "early reflections" and
> so on. The 3-D processing involves solution of the wave equation in
> three dimensions, providing a solid physical basis. I have found that
> far less tweaking is necessary for this approach than with the usual
> DSP-oriented processing that is the norm.
>
> As Mark Knecht wrote, this approach lends itself more to
> preprocessing, or determining in advance what processing to do, then
> doing it. The good news is that the result will be closer to
> something you can use than it would be using the normal
> mixing/processing approach. The bad news is that the best way to use
> this new approach is to rethink the whole process of mixing and
> mastering.
>
>
> ToPlug-In or not to Plug-In:
>
> Some people would like to see this implemented as a plugin, but that's
> putting something new in an old container --- which can be done, but
> one has to ask if that's really what one wants to do. If so, then I'd
> be happy to do it, but in the long run, it may be better to rethink
> the whole process.
>
> The mathematical basis for all of this is the solution of the wave
> equation. Once you've developed methods for doing that in 1-, 2-, and
> 3-D, you can build a reverber/echoer/stereo-separator OR you can build
> an SF2 generator OR LOTS of other things. If I were to make these
> programs available for someone else, how shall I package them? I
> could build any one of a number of different programs that utilize the
> routines I've developed, each of which can do completely different
> things. So rather than speak to developers about how to improve my
> programs or something like that which was suggested, I really need to
> speak with potential users about what they might need or want, whether
> that be a plugin or something completely different.
>
> For example, these same programs can also be used to create
> instruments. (A room can be regarded as part of a three-dimensional
> instrument.) One could solve the wave equation in two dimensions
> (drums, cymbals, etc.), in one dimension (guitars, pianos, etc.) or in
> other geometries (for example pipes --- organs, and so on).
>
>
> On the approach used --- IR?:
>
> Mark Knecht asked whether or not this work was IR-based. I assume
> that this means "impulse response" function based. Well, yes this is
> how the user would see the application of 3-D processing at the very
> end of the line, but there is a lot else going on. First one needs to
> generate the impulse response functions, then generate the impulses,
> then generate the "recorded" signals. The recorded signals can be
> decomposed into subcomponents (for example split into frequency
> bands), then the various impulse response functions can be applied.
> The programs I've written do all of this, so it's much more than
> writing a plugin. If I were to merely do that simple part of it, then
> I'd have to supply some "canned" impulse response functions and
> transfer some information on how to utilize them properly (or
> improperly like I do!). I could do this, but I suspect soon enough
> people would want more information or additional impulse response
> functions. The "IR" application step is the simplest part of this
> whole process.
>
>
> On documentation:
>
> Jörn asked about whether or not the code was documented so that one
> could see what was going on. No, it's really not. Some sort of
> instruction would be necessary, and I'd have to generate that. I'm
> not aware of anywhere else I could point one to, either. This is
> rather original work I've done, and the information is scattered about
> in mathematical physics textbooks, books on acoustics, and in books on
> signal processing. It is done in C++, so some of the code is in a
> library --- but some of that may also be of interest. One thing I did
> was to start completely from scratch. You don't need anything else
> other than a C++ library to link to. The scripts are Korn shell with
> a little Python.
>
>
> What next?
>
> To summarize a little bit: I can do a lot of different things here,
> depending upon what people are interested in. I can try to write a
> plugin that applies impulse response functions that I have generated;
> I could perhaps make available the programs for producing them; I
> could write a program that assists in applying them; I could write an
> instrument generator; I could release a library of the utilities. Or
> I could just do what Jörn suggested and wrap up what I've already
> done. I suspect this would be the least useful approach for most
> people, but the best approach for me and for potential collaborators.
>
> Thanks once again for your comments and for listening to the demo.
> I'd appreciate further discussion, either here or privately by email.
> I've got a little more on the idea of a plugin and on real-time
> concerns which I'll send a little later.
>
>
>
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