>Mastering engineers can hear truncation error at the 24th bit but say it is >subtle and may require experience or training to pick up.
Quick observations: 1) The output step size of the lsb is full-scale / 2^24. If full-scale is 1V, then step is 0.0000000596046447753906V, or 0.0596 microvolt (millionths of a volt). Hearing capabilities aside, the converter must be able to resolve this, and it must make it through the thermal (and other) noise of their equipment and move a speaker. If you’re not an electrical engineer, it may be difficult to grasp the problem that this poses. 2) I happened on a discussion in an audio forum, where a highly-acclaimed mastering engineer and voice on dither mentioned that he could hear the dither kick in when he pressed a certain button in the GUI of some beta software. The maker of the software had to inform him that he was mistaken on the function of the button, and in fact it didn’t affect the audio whatsoever. (I’ll leave his name out, because it’s immaterial—the guy is a great source of info to people and is clearly excellent at what he does, and everyone who works with audio runs into this at some point.) The mastering engineer graciously accepted his goof. 3) Mastering engineers invariably describe the differences in very subjective term. While this may be a necessity, it sure makes it difficult to pursue any kind of validation. From a mastering engineer to me, yesterday: 'To me the truncated version sounds colder, more glassy, with less richness in the bass and harmonics, and less "front to back" depth in the stereo field.’ 4) 24-bit audio will almost always have a far greater random noise floor than is necessary to dither, so they will be self-dithered. By “almost”, I mean that very near 100% of the time. Sure, you can create exceptions, such as synthetically generated simple tones, but it’s hard to imagine them happening in the course of normal music making. There is nothing magic about dither noise—it’s just mimicking the sort of noise that your electronics generates thermally. And when mastering engineers say they can hear truncation distortion at 24-bit, they don’t say “on this particular brief moment, this particular recording”—they seems to say it in general. It’s extremely unlikely that non-randomized truncation distortion even exists for most material at 24-bit. My point is simply that I’m not going to accept that mastering engineers can hear the 24th bit truncation just because they say they can. > On Feb 6, 2015, at 5:21 AM, Vicki Melchior <vmelch...@earthlink.net> wrote: > > The following published double blind test contradicts the results of the old > Moran/Meyer publication in showing (a) that the differences between CD and > higher resolution sources is audible and (b) that failure to dither at the > 16th bit is also audible. > > http://www.aes.org/e-lib/browse.cfm?elib=17497 > > The Moran/Meyer tests had numerous technical problems that have long been > discussed, some are enumerated in the above. > > As far as dithering at the 24th bit, I can't disagree more with a conclusion > that says it's unnecessary in data handling. Mastering engineers can hear > truncation error at the 24th bit but say it is subtle and may require > experience or training to pick up. What they are hearing is not noise or > peaks sitting at the 24th bit but rather the distortion that goes with > truncation at 24b, and it is said to have a characteristic coloration effect > on sound. I'm aware of an effort to show this with AB/X tests, hopefully it > will be published. The problem with failing to dither at 24b is that many > such truncation steps would be done routinely in mastering, and thus the > truncation distortion products continue to build up. Whether you personally > hear it is likely to depend both on how extensive your data flow pathway is > and how good your playback equipment is. > > Vicki Melchior > > On Feb 5, 2015, at 10:01 PM, Ross Bencina wrote: > >> On 6/02/2015 1:50 PM, Tom Duffy wrote: >>> The AES report is highly controversial. >>> >>> Plenty of sources dispute the findings. >> >> Can you name some? >> >> Ross. >> -- -- dupswapdrop -- the music-dsp mailing list and website: subscription info, FAQ, source code archive, list archive, book reviews, dsp links http://music.columbia.edu/cmc/music-dsp http://music.columbia.edu/mailman/listinfo/music-dsp
