ruffrecords
Well-known member
Does this not simply demonstrate that there is absolutely no more information in a 24/192 data stream than there is in a 24/48 stream if the sampled signal is below 48K/2 .
Cheers
Ian
Cheers
Ian
The limits of audibility are well studied but is relatively easy to just deliver 20-20kHz and not worry about it.bluebird said:I think people should actually loosen the boundaries of audible sound a bit. When doing a simple tone sweep I can't hear above 17K as a guy in his 40's. My kid says he might be able to "feel" the tone a bit above 18K if its loud enough. But that's still 2000hz away from 20K.
IMD is not "air" more like LF grunge...Does it really matter if there is inter-modulation distortion around 19 or 20K anyhow? Maybe thats the "air" people hear sometimes. Maybe crappy converters with bad filters will come back like vinyl did!
Dan Lavry's work wrt sample rate and a/d conversion is very well respected , but I doubt he discounts HF linearity (IMD).P.S. Anyone going down the sample rate rabbit hole should read Dan Lavery's papers.
http://www.lavryengineering.com/pdfs/lavry-white-paper-the_optimal_sample_rate_for_quality_audio.pdf
IMD is caused by non-linearity... When a pure tone is distorted by non-linearity it creates (higher) harmonic overtones. When multiple tones are distorted by non-linearities the distortion products are (higher and lower) sum and difference frequencies.bluebird said:Oops corrected the spelling.
Thanks John, I was just asking as I don't know much about IMD or its effects. Looks like I should study up on it a bit. I just got an AP system one and believe there are tests you can set up for testing IMD.
Do you know if low pass filters in digital conversion cause IMD? Or just resonant peaks around the cutoff frequency?
john12ax7 said:Also, in my case 192 was worse than 96.
The gold standard for pitch shifting back in the day involved what was called a "rotating head" tape machine. Four(?) heads were wired in parallel and spaced around a revolving drum that was in contact with the moving tape. By varying the rotation velocity of the head assembly you could shift the pitch of the recorded material up/down. (This is similar to how VCRs work but for a different reason, VCRs need to trick the tape/head into high velocity relative to the actual tape speed to record and playback the HF video content. )kambo said:timestretch algorithms are getting better for sure.
JohnRoberts said:The gold standard for pitch shifting back in the day involved what was called a "rotating head" tape machine.
JR
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