Hi Michael, I know that you already understand this, and comment that this is for internal calculations, but for the sake of anyone who might misinterpret your 32-bit vs 64-bit comment, I’ll point out that this is a situation of error feedback—the resulting error is much greater than the sample sizes you’re talking about, and can result in differences far above the 24-bit level. A simple example is the ubiquitous direct form I biquad, which goes all to hell in lower audio frequencies with 24-bit storage (unless you noise shape or increase resolution).
Nigel > On Feb 6, 2015, at 10:24 AM, Michael Gogins <michael.gog...@gmail.com> wrote: > > Do not believe anything that is not confirmed to a high degree of > statistical signifance (say, 5 standard deviations) by a double-blind > test using an ABX comparator. > > That said, the AES study did use double-blind testing. I did not read > the article, only the abstract, so cannot say more about the study. > > In my own work, I have verified with a double-blind ABX comparator at > a high degree of statistical significance that I can hear the > differences in certain selected portions of the same Csound piece > rendered with 32 bit floating point samples versus 64 bit floating > point samples. These are sample words used in internal calculations, > not for output soundfiles. What I heard was differences in the sound > of the same filter algorithm. These differences were not at all hard > to hear, but they occurred in only one or two places in the piece. > > I have not myself been able to hear differences in audio output > quality between CD audio and high-resolution audio, but when I get the > time I may try again, now that I have a better idea what to listen > for. > > Regards, > Mike > > > > ----------------------------------------------------- > Michael Gogins > Irreducible Productions > http://michaelgogins.tumblr.com > Michael dot Gogins at gmail dot com > > > On Fri, Feb 6, 2015 at 1:13 PM, Nigel Redmon <earle...@earlevel.com> wrote: >>> 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 > -- > 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 -- 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
