Phil Leigh;572649 Wrote: > No need to be humble when you are correct! :-) > > The point is it really isn't that hard. > > Say you've got a 24/96 file with significant content between 22-40k > > First, apply a savage high-pass filter and takes out everything below > (say) 22k. > Then apply a constant-time pitch shift to bring the residual content > down to between 1-2k (That's quite a big shift - 5 octaves or so). > > What's left will be pretty obvious - either it's uncorrelated noise or > it's the upper harmonics of instruments (mostly cymbals and other > percussive instruments) in the original recording, which will follow > the "beat" of the music. You can easily see & hear which it is. > If you play the two files side by side it should still sound like > music... > > If you want to experiment, get hold of some DVD-A's... > > You can do all this with Audacity (which is free). > > Another method is to compare a DVD-A with its upsampled redbook > equivalent using AudioDiffMaker - this will null out the common > content, leaving just the extra information on the DVD-A - again, since > this will mostly be above the fringe of peoples hearing you need to > pitch-shift it down to understand it - but you can see straight away on > the screen if it's just noise or something that correlates to the > music. > > > If you are imagining that someone would maliciously or creatively pass > a 16/44 track through a software or hardware "harmonics generator" to > create false correlated info above 22k - yes, that is essentially a > variation on the reverse of the process I've just described. > > That's broadly how an Aphex Aural Exciter used to work - albeit not at > the supersonic frequencies - (Rumours/Fleetwood Mac, anyone?). > > However, if you just add white/pink/otherwise shaped noise to a track > it will be obvious. > > If you have what appear to be correlated harmonics of the music it's > impossible to tell if they were on the original recording "multi-track" > masters or artificially generated afterwards, since that is a legitimate > "effect" used in pop/rock mastering frequently anyway! (I'be never heard > of it being done on classical but that's not my field - I'd be > surprised.) > > This is where common sense comes in. What age is the original master? > What equipment was likely to have been used to capture the original > sound? What effects were available then? > > If you can find a real-world example of a DVD-A, SACD or high-rez > download where you suspect that the recording has been "remastered" by > adding HF noise rather than musically correlated upper harmonics we can > pursue this further...
Ssssh.. you just telled them how to do it :) ! Run track through aural exciter(or similar modern plugin) diff the output pitch shift the diff a couple of octaves up add to original track at suitable lower level to mimick that out put has faded a bit, or if ambitious filter at a slope that mimics popular microphones hf behavior, probably not very linear anymore.. Why all this bothering with SACD's anyway ? most music are of non DSD source anyway so a better fidelity 24/48 or 24/96 file must be somewhere ? They actually don't care enough to send a proper file, the reseller has to had it ripped. -- Mnyb -------------------------------------------------------------------- Main hifi: Touch + CIA PS +MeridianG68J MeridianHD621 and assorted amps SiriuS, Classe' Primare and Dynadio speakers, Contour 4 Contour Center, and Contour 1.3SE for the rear ch. Rel Stadium 3 sub. Bedroom/Office: Boom Kitchen: SB3 + powered Fostex PM0.4 Miscellaneous use: Radio (with battery) I use a Controller various ir-remotes and a Eee-PC with squeezeplay to control this ------------------------------------------------------------------------ Mnyb's Profile: http://forums.slimdevices.com/member.php?userid=4143 View this thread: http://forums.slimdevices.com/showthread.php?t=74688 _______________________________________________ Touch mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/touch
