robert bristow-johnson wrote:> in article 1158180465.381809.175420@i3g2000cwc.googlegroups.com, Andor at > andor.bariska@gmail.com wrote on 09/13/2006 16:47: > > > robert bristow-johnson wrote: > > > >>> robert bristow-johnson wrote: > >>> > >>> ... > >>>> not to discourage the time-domain splicing technique (sometimes it > >>>> works very well) but, if the application is to polyphonic music, TDHS > >>>> might leave glitches because the automated process will find *no* > >>>> decently matched places to splice. > >>> > >>> Robert, > >>> > >>> what in your opinion would be an appropriate procedure for time scaling > >>> a measured room response? > >> > >> you mean to make a little reverberant room sound like a big reverberant room > >> (without reducing the bandwidth of the reverberations)? i never thunked of > >> that before. > >> > >> why would you want to do that? you wouldn't be getting a "true" reverb > >> sound as you would if you went into some cathedral, measured the impulse > >> response, and used that in some massive convolution machine. > > > > But you could scale the cathedral down to a match box if you can time > > compress the impulse response. > > but you lose information. i don't see how time-compressing a cathedral > impulse response (assuming it's a "good" sounding space) would have any > promise of creating a "good" sounding impulse response for a smaller room.Who knows - I don't know what it would sound like, but perhaps it results in usable impulse responses? It's worth a try.> > > I had a look at some of the impulse responses of the pure time and pure > > frequency methods at http://www.dspdimension.com. They produce multiple > > copies of the single main pulse, which would of course be catastrophic > > for a reverb. > > any discrete reflection will be a copy of the main pulse. "good" sounding > spaces have *some* discrete reflections, often the "early reflections", but > that the reflections of the reflections become more and more diffuse and > eventually the impulse response looks like some kinda white noise with an > exponentially decaying envelope.Yes, the noisy tail shouldn't pose much of a problem. But the magic of a good impulse response lies in the early reflections. Now if you mess up the early reflections by arbitrarily placing copies of each reflection somewhere around the start of the impulse response, you'll destroy the information which defines the geometry of the space (cathedral). The trick (I think) is to just scale the parts in between the early reflections.
speed, pitch and tempo
Started by ●September 12, 2006
Reply by ●September 14, 20062006-09-14
Reply by ●September 15, 20062006-09-15
in article 1158267316.972136.20720@h48g2000cwc.googlegroups.com, Andor at andor.bariska@gmail.com wrote on 09/14/2006 16:55:> > robert bristow-johnson wrote: > >> in article 1158180465.381809.175420@i3g2000cwc.googlegroups.com, Andor at >> andor.bariska@gmail.com wrote on 09/13/2006 16:47: >> >>> robert bristow-johnson wrote: >>> >>>>> robert bristow-johnson wrote: >>>>> >>>>> ... >>>>>> not to discourage the time-domain splicing technique (sometimes it >>>>>> works very well) but, if the application is to polyphonic music, TDHS >>>>>> might leave glitches because the automated process will find *no* >>>>>> decently matched places to splice. >>>>> >>>>> Robert, >>>>> >>>>> what in your opinion would be an appropriate procedure for time scaling >>>>> a measured room response? >>>> >>>> you mean to make a little reverberant room sound like a big reverberant >>>> room >>>> (without reducing the bandwidth of the reverberations)? i never thunked of >>>> that before. >>>> >>>> why would you want to do that? you wouldn't be getting a "true" reverb >>>> sound as you would if you went into some cathedral, measured the impulse >>>> response, and used that in some massive convolution machine. >>> >>> But you could scale the cathedral down to a match box if you can time >>> compress the impulse response. >> >> but you lose information. i don't see how time-compressing a cathedral >> impulse response (assuming it's a "good" sounding space) would have any >> promise of creating a "good" sounding impulse response for a smaller room. > > Who knows - I don't know what it would sound like, but perhaps it > results in usable impulse responses? It's worth a try. >be my guest. please! and please tell us how it turns out. it could be worth an AES convention/conference paper. i dunno.>> >>> I had a look at some of the impulse responses of the pure time and pure >>> frequency methods at http://www.dspdimension.com. They produce multiple >>> copies of the single main pulse, which would of course be catastrophic >>> for a reverb. >> >> any discrete reflection will be a copy of the main pulse. "good" sounding >> spaces have *some* discrete reflections, often the "early reflections", but >> that the reflections of the reflections become more and more diffuse and >> eventually the impulse response looks like some kinda white noise with an >> exponentially decaying envelope. > > Yes, the noisy tail shouldn't pose much of a problem. But the magic of > a good impulse response lies in the early reflections. Now if you mess > up the early reflections by arbitrarily placing copies of each > reflection somewhere around the start of the impulse response, you'll > destroy the information which defines the geometry of the space > (cathedral).for a particular space, certainly moving around the early reflections at random will change the character of the room. there might be some yet undiscovered algorithm of moving the early reflections around with the perceptual property that nearly everyone cannot hear the difference. that wouldn't surprize me but i dunno.> The trick (I think) is to just scale the parts in between > the early reflections.dunno about that either. -- r b-j rbj@audioimagination.com "Imagination is more important than knowledge."
