nicolas75;572562 Wrote: > Well I've met some really good sound engineers, but they are usually > more humble than you are ... > You may be right, but I would be curious to see how it is "soooo easy" > as you say. :-) > > Those (bad ?) sound engineers would be very happy to learn from > somebody as smart as you are :-)
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... -- Phil Leigh You want to see the signal path BEFORE it gets onto a CD/vinyl...it ain't what you'd call minimal... Touch(wired/XP) - TACT 2.2X (Linear PSU) + Good Vibrations S/W - MF Triplethreat(Audiocom full mods) - Linn 5103 - Aktiv 5.1 system (6x LK140's, ESPEK/TRIKAN/KATAN/SEIZMIK 10.5), Pekin Tuner, Townsend Supertweeters, Blue Jeans Digital,Kimber Speaker & Chord Interconnect cables Kitchen Boom, Outdoors: SB Radio, Harmony One remote for everything. ------------------------------------------------------------------------ Phil Leigh's Profile: http://forums.slimdevices.com/member.php?userid=85 View this thread: http://forums.slimdevices.com/showthread.php?t=74688 _______________________________________________ Touch mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/touch
