Re: [PD] Equal-power crossfade?
Hi, On Mon, Feb 06, 2012 at 02:22:34PM +0100, Pierre Massat wrote: I need a simple equal-power crossfade between two signals. I asked the same question a few years ago, but i just can't remember how to do it... This is used in rj's e_pan.pd: left = cos(p) * signal right = sin(p) * signal where p is in radians from 0 to PI/2 (i.e. multiply your 0...1 panning by 1.5708...) Ciao -- Frank BarknechtDo You RjDj.me? _ __footils.org__ ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Equal-power crossfade?
Thanks Frank! Pierre 2012/2/6 Frank Barknecht f...@footils.org Hi, On Mon, Feb 06, 2012 at 02:22:34PM +0100, Pierre Massat wrote: I need a simple equal-power crossfade between two signals. I asked the same question a few years ago, but i just can't remember how to do it... This is used in rj's e_pan.pd: left = cos(p) * signal right = sin(p) * signal where p is in radians from 0 to PI/2 (i.e. multiply your 0...1 panning by 1.5708...) Ciao -- Frank BarknechtDo You RjDj.me? _ __footils.org__ ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Equal-power crossfade?
Here's an argument for plain linear crossfade. I get power boosts with cosine crossfades... best, J On Mon, Feb 6, 2012 at 8:53 AM, Pierre Massat pimas...@gmail.com wrote: Thanks Frank! Pierre 2012/2/6 Frank Barknecht f...@footils.org Hi, On Mon, Feb 06, 2012 at 02:22:34PM +0100, Pierre Massat wrote: I need a simple equal-power crossfade between two signals. I asked the same question a few years ago, but i just can't remember how to do it... This is used in rj's e_pan.pd: left = cos(p) * signal right = sin(p) * signal where p is in radians from 0 to PI/2 (i.e. multiply your 0...1 panning by 1.5708...) Ciao -- Frank Barknecht Do You RjDj.me? _ __footils.org__ ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list -- Jaime E Oliver LR jo2...@columbia.edu www.jaimeoliver.pe 858 750 0924 (cel) linear-cross.pd Description: Binary data ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Equal-power crossfade?
There are some pan algorithms in the 'pan' library also, included in Pd-extended. They're all pd abstractions. .hc On Feb 6, 2012, at 9:29 AM, Jaime Oliver wrote: Here's an argument for plain linear crossfade. I get power boosts with cosine crossfades... best, J On Mon, Feb 6, 2012 at 8:53 AM, Pierre Massat pimas...@gmail.com wrote: Thanks Frank! Pierre 2012/2/6 Frank Barknecht f...@footils.org Hi, On Mon, Feb 06, 2012 at 02:22:34PM +0100, Pierre Massat wrote: I need a simple equal-power crossfade between two signals. I asked the same question a few years ago, but i just can't remember how to do it... This is used in rj's e_pan.pd: left = cos(p) * signal right = sin(p) * signal where p is in radians from 0 to PI/2 (i.e. multiply your 0...1 panning by 1.5708...) Ciao -- Frank BarknechtDo You RjDj.me? _ __footils.org__ ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list -- Jaime E Oliver LR jo2...@columbia.edu www.jaimeoliver.pe 858 750 0924 (cel) linear-cross.pd___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list 'You people have such restrictive dress for women,’ she said, hobbling away in three inch heels and panty hose to finish out another pink-collar temp pool day. - “Hijab Scene #2, by Mohja Kahf ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Equal-power crossfade?
Make sure to use the interval 0 - Pi/2, panning beyond will only crossfade back and forth On 6 February 2012 15:29, Jaime Oliver jaime.oliv...@gmail.com wrote: Here's an argument for plain linear crossfade. I get power boosts with cosine crossfades... best, J On Mon, Feb 6, 2012 at 8:53 AM, Pierre Massat pimas...@gmail.com wrote: Thanks Frank! Pierre 2012/2/6 Frank Barknecht f...@footils.org Hi, On Mon, Feb 06, 2012 at 02:22:34PM +0100, Pierre Massat wrote: I need a simple equal-power crossfade between two signals. I asked the same question a few years ago, but i just can't remember how to do it... This is used in rj's e_pan.pd: left = cos(p) * signal right = sin(p) * signal where p is in radians from 0 to PI/2 (i.e. multiply your 0...1 panning by 1.5708...) Ciao -- Frank Barknecht Do You RjDj.me? _ __footils.org__ ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list -- Jaime E Oliver LR jo2...@columbia.edu www.jaimeoliver.pe 858 750 0924 (cel) ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Equal-power crossfade?
On Mon, Feb 06, 2012 at 02:42:01PM +0100, Frank Barknecht wrote: Hi, On Mon, Feb 06, 2012 at 02:22:34PM +0100, Pierre Massat wrote: I need a simple equal-power crossfade between two signals. I asked the same question a few years ago, but i just can't remember how to do it... This is used in rj's e_pan.pd: left = cos(p) * signal right = sin(p) * signal where p is in radians from 0 to PI/2 (i.e. multiply your 0...1 panning by 1.5708...) Oh, well, actually you were looking for crossfade, not panning. It's basically the same idea, though. In the rj library you could use [c_cpxfade]. The helpfile for this compares it with the linear [c_xfade] which has the hole in the middle. Ciao -- Frank BarknechtDo You RjDj.me? _ __footils.org__ ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Equal-power crossfade?
On Mon, Feb 06, 2012 at 09:29:33AM -0500, Jaime Oliver wrote: Here's an argument for plain linear crossfade. I get power boosts with cosine crossfades... Your example is a bit broken (there is no panning going on at all), but I get the same result with a the fixed version or with [e_pan] in the rj library when adding left and right signal together and taking the RMS. The boost in the center is to be expected: In the center with CP-panning, left and right channels both are multiplied by about 0.707 instead of 0.5 with a linear pan, so adding them together will make the center louder. Perception-wise this results in the signal appearing nearer to you than with linear panning, which is the reason this is used: With CP-panning the signal will appear to move around you in a constant circle whereas with linear panning it will move farther away from you as it gets to the center, it will move as if on an oval. Avoiding this kind of movement is the motivation for CP-panning. Ciao -- Frank BarknechtDo You RjDj.me? _ __footils.org__ ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Equal-power crossfade?
Here's an argument for plain linear crossfade. I get power boosts with cosine crossfades... best, J You'll want to use linear crossfades for correlated signals (similar spectrum and same phase), cosine for non-correlated signals (noise, different frequencies, arbitrary phase, etc.). Of course for similar signals with arbitrary phase, there's no guarantee that the output will really be constant power, since you could get cancellations or reinforcements. But unless you know in advance that the phases are correlated, it's best to use a cosine crossfade. Incidentally I'm working on a frequency domain algorithm that forces mixed signals to be correlated and in phase, by summing their magnitudes. But it's no magic trick since it does this by inducing a time varying phase shift. This isn't the silver bullet that you might be hoping for, but I think it should make a neat variation of the usual chorus effect. ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Equal-power crossfade?
Your example is a bit broken (there is no panning going on at all), you're right. ... coffee excuse ... here is a fixed version in case someone is interested. the subject of the e-mail however, does not ask to pan, but to crossfade without loosing or adding power. What the example shows is a linear crossfade where the RMS remains constant during the crossfade. best, J -- Jaime E Oliver LR jo2...@columbia.edu www.jaimeoliver.pe 858 750 0924 (cel) linear-cross.pd Description: Binary data ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Equal-power crossfade?
On Mon, Feb 06, 2012 at 10:15:51AM -0800, Jaime Oliver wrote: Your example is a bit broken (there is no panning going on at all), you're right. ... coffee excuse ... here is a fixed version in case someone is interested. the subject of the e-mail however, does not ask to pan, but to crossfade without loosing or adding power. Yeah, I confused that right from the start ... missing-coffee-excuse ... What the example shows is a linear crossfade where the RMS remains constant during the crossfade. This has its roots indeed in the use of fading identical signal(s). If you use different input sounds, the CP-fade gives nicer results. Attached is an example that uses the linear/cp crossfades from the rj-library as subpatches and fades two different signals and then the same signal twice. Ciao -- Frank BarknechtDo You RjDj.me? _ __footils.org__ crossfade-compare.pd Description: application/puredata ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Equal-power crossfade?
All very interesting stuff, thanks! I didn't need anything too special so i've adapted Hans' equal-power pan (I've turned it upside down to make a crossfader). I only needed it for the ring modulator patch i've just posted on my blog ( http://guitarextended.wordpress.com/2012/02/06/ring-modulator-effect-using-pure-data/ ) Cheers! Pierre 2012/2/6 Frank Barknecht f...@footils.org On Mon, Feb 06, 2012 at 10:15:51AM -0800, Jaime Oliver wrote: Your example is a bit broken (there is no panning going on at all), you're right. ... coffee excuse ... here is a fixed version in case someone is interested. the subject of the e-mail however, does not ask to pan, but to crossfade without loosing or adding power. Yeah, I confused that right from the start ... missing-coffee-excuse ... What the example shows is a linear crossfade where the RMS remains constant during the crossfade. This has its roots indeed in the use of fading identical signal(s). If you use different input sounds, the CP-fade gives nicer results. Attached is an example that uses the linear/cp crossfades from the rj-library as subpatches and fades two different signals and then the same signal twice. Ciao -- Frank BarknechtDo You RjDj.me? _ __footils.org__ ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Equal-power crossfade?
Le 2012-02-06 à 14:42:00, Frank Barknecht a écrit : On Mon, Feb 06, 2012 at 02:22:34PM +0100, Pierre Massat wrote: I need a simple equal-power crossfade between two signals. I asked the same question a few years ago, but i just can't remember how to do it... This is used in rj's e_pan.pd: left = cos(p) * signal right = sin(p) * signal where p is in radians from 0 to PI/2 (i.e. multiply your 0...1 panning by 1.5708...) That's for panning, not for crossfading. crossfading is similar, but is the other way around : signal = left * cos(p) + right * sin(p) But if left=-right (opposite phase) then the crossfade will quickly fade out to silence and back in ; and if left=right, then your power gain will be (cos(p)+sin(p))² = cos²(p)+2sin(p)cos(p)+sin²(p) = 1+2sin(p)cos(p) = 1+sin(2p). This goes up to double power (amplitude is multiplied by 1,414). Generally speaking, as long as L and R don't have frequencies in common, this works perfectly, but as soon as they do, you have to do proper phase addition : the cosines are added separately from the sines : if you know a sinusoïd by its amplitude and phase offset, convert to cartesian before adding... this will show you how such things add up. __ | Mathieu BOUCHARD - téléphone : +1.514.383.3801 - Montréal, QC___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Equal-power crossfade?
Le 2012-02-06 à 13:13:00, Scott Nordlund a écrit : Incidentally I'm working on a frequency domain algorithm that forces mixed signals to be correlated and in phase, by summing their magnitudes. But it's no magic trick since it does this by inducing a time varying phase shift. This isn't the silver bullet that you might be hoping for, but I think it should make a neat variation of the usual chorus effect. This means you do FFT, then convert to polar, then do linear crossfade in the shortest of the two paths ? (so that the phase shift is always between -π and +π) If you do it quickly, it becomes a pitch shift, but if not panning too fast, it shouldn't be a problem. __ | Mathieu BOUCHARD - téléphone : +1.514.383.3801 - Montréal, QC___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
Re: [PD] Equal-power crossfade?
Le 2012-02-06 à 13:13:00, Scott Nordlund a écrit : Incidentally I'm working on a frequency domain algorithm that forces mixed signals to be correlated and in phase, by summing their magnitudes. But it's no magic trick since it does this by inducing a time varying phase shift. This isn't the silver bullet that you might be hoping for, but I think it should make a neat variation of the usual chorus effect. This means you do FFT, then convert to polar, then do linear crossfade in the shortest of the two paths ? (so that the phase shift is always between -π and +π) If you do it quickly, it becomes a pitch shift, but if not panning too fast, it shouldn't be a problem. It's not specifically intended for a crossfader (though it could easily be used that way), just summing in general. It's a typical weighted-overlap-add FFT thing. The magnitude of the output is the sum of the input magnitudes (so they're effectively always in phase and never cancel). The phase can be a number of things: the phase of the sum of the inputs (i.e. the phase of the usual vector sum), or the phase of the input with the largest magnitude (per bin), or either of those but constrained to be within a certain range with respect to one of the inputs... or something like that. I haven't had a lot of time to mess with it, but it's been in the back of my mind as a generally neat idea. ___ Pd-list@iem.at mailing list UNSUBSCRIBE and account-management - http://lists.puredata.info/listinfo/pd-list
