Yes, I disagree with the "always". "Not always needed" means "it's sometimes
needed", my point is that it's never needed, until proven otherwise. Your
video proves that sometimes it's not needed, but not that sometimes it's
needed.
-----Message d'origine-----
From: Nigel Redmon
Sent: Wednesday, February 04, 2015 6:51 PM
To: A discussion list for music-related DSP
Subject: Re: [music-dsp] Dither video and articles
I totally understood the point of your video, that dithering to 16bit isn't
always needed - but that's what I disagree with.
Sorry, Didier, I’m confused now. I took from your previous message that you
feel 16-bit doesn’t need to be dithered ("dithering to 16bit will never make
any audible difference”). Here you say that you disagree with "dithering to
16bit isn't always needed”. In fact, you are saying that it’s never
needed—you disagree because “isn’t always needed” implies that it is
sometimes needed—correct?
On Feb 4, 2015, at 5:06 AM, Didier Dambrin <di...@skynet.be> wrote:
Then, it’s no-win situation, because I could EASILY manufacture a bit of
music that had significant truncation distortion at 16-bit.
Please do, I would really like to hear it.
I have never heard truncation noise at 16bit, other than by playing with
levels in a such a way that the peaking parts of the rest of the sound
would destroy your ears or be very unpleasant at best. (you say 12dB, it's
already a lot)
I totally understood the point of your video, that dithering to 16bit
isn't always needed - but that's what I disagree with.
-----Message d'origine----- From: Nigel Redmon
Sent: Wednesday, February 04, 2015 10:59 AM
To: A discussion list for music-related DSP
Subject: Re: [music-dsp] Dither video and articles
Hi Didier—You seem to find contradictions in my choices because you are
making the wrong assumptions about what I’m showing and saying.
First, I’m not steadfast that 16-bit dither is always needed—and in fact
the point of the video was that I was showing you (the viewers) how you
can judge it objectively for yourself (and decide whether you want to
dither). This is a much better way that the usual that I hear from people,
who often listen to the dithered and non-dithered results, and talk about
the "soundstage collapsing" without dither, “brittle” versus “transparent"
, etc.
But if I’m to give you a rule of thumb, a practical bit of advice that you
can apply without concern that you might be doing something wrong in a
given circumstance, that advice is “always dither 16-bit reductions”.
First, I suspect that it’s below the existing noise floor of most music
(even so, things like slow fades of the master fader might override that,
for that point in time). Still, it’s not hard to manufacture something
musical that subject to bad truncation distortion—a naked, low frequency,
low-haromic-content sound (a synthetic bass or floor tom perhaps). Anyway,
at worst case, you’ve added white noise that you are unlikely to hear—and
if you do, so what? If broadband noise below -90 dB were a deal-breaker in
recorded music, there wouldn’t be any recorded music. Yeah, truncation
distortion at 16-bits is an edge case, but the cost to remove it is almost
nothing.
You say that we can’t perceive quantization above 14-bit, but of course we
can. If you can perceive it at 14-bit in a given circumstance, and it’s an
extended low-level passage, you can easily raise the volume control
another 12 dB and be in the same situation at 16-bit. Granted, it’s most
likely that the recording engineer hears it and not the end-listener, but
who is this video aimed at if not the recording engineer? He’s the one
making the choice of whether to dither.
Specifically:
..then why not use a piece of audio that does prove the point, instead? I
know why, it's because you can’t...
First, I would have to use my own music (because I don’t own 32-bit float
versions of other peoples’ music, even if I thought it was fair use to of
copyrighted material). Then, it’s no-win situation, because I could EASILY
manufacture a bit of music that had significant truncation distortion at
16-bit. I only need to fire up one of my soft synths, and ring out some
dull bell tones and bass sounds. Then people would accuse me of fitting
the data to the theory, and this isn’t typical music made in a typical
high-end study by a professional engineer. And my video would be 20
minutes long because I’m not looking at a 40-second bit of music any more.
Instead, I clearly explained my choice, and it proved to be a pretty good
one, and probably fairly typical at 16-bit, wouldn’t you agree? As I
mentioned at the end of the video, the plan is to further examine some
high-resolution music that a Grammy award-winning engineer and producer
friend of mine has said he will provide.
...and dithering to 16bit will never make any audible difference.
If you mean “never make any audible difference” in the sense that it won’t
matter one bit to sales or musical enjoyment, I agree. I imagine
photographers make fixes and color tweaks that will never be noticed in
the magazine or webpage that the photo will end up in either. But I
guarantee you, there are lots of audio engineers that will not let that
practically (using the word in the original “practical" sense–don’t read
as “almost") un-hearable zipper in the fade go. If they know it’s there,
and in some cases they CAN actually hear it, with the volume cranked, you
can tell them all day and all night that they are wasting there time
dithering, because listeners will never hear it, but they will want to get
rid of it. And the cost of that rash action to get rid of it? Basically
nothing. Hence my advice: Dither and don’t worry about it—or listen to the
residual up close and see if there’s nothing to worry about, if you
prefer.
On Feb 3, 2015, at 10:24 PM, Didier Dambrin <di...@skynet.be> wrote:
Sorry, but if I sum up this video, it goes like this:
you need dithering to 16bit and I'm going to prove it, then the video
actually proves that you don't need it starting at 14bit, but adds "it's
only because of the nature of the sound I used for demo".
..then why not use a piece of audio that does prove the point, instead?
I know why, it's because you can't, and dithering to 16bit will never
make any audible difference.
It's ok to tell the world to dither to 16bit, because it's nothing
harmful either (it only mislays people from the actual problems that
matter in mixing). But if there is such a piece of audio that makes
dithering to 16bit any audible, without an abnormally massive boost to
hear it, I'd like to hear it.
Andrew says he agrees, but then adds that it's important when you
post-edit the sound. Yes it is, totally, but if you're gonna post-edit
the sound, you will rather keep it 32 or 24bit anyway - the argument
about dithering to 16bit is for the final mix.
To me, until proven otherwise, for normal-to-(not abnormally)-high
dynamic ranges, we can't perceive quantization above 14bit for audio, and
10bits for images on a screen (debatable here because monitors aren't
linear but that's another story). Yet people seem to care less about
images, and there's gradient banding all over the place.
-----Message d'origine----- From: Andrew Simper
Sent: Wednesday, February 04, 2015 6:06 AM
To: A discussion list for music-related DSP
Subject: Re: [music-dsp] Dither video and articles
Hi Nigel,
Isn't the rule of thumb in IT estimates something like: "Double the
time you estimated, then move it up to the next time unit"? So 2 weeks
actually means 4 months, but since we're in Music IT I think we should
be allowed 5 times instead of 2, so from my point of view you've
actually delivered on time ;)
Thanks very much for doing the video! I agree with your recommended
workflows of 16 bit = always dither, and 24 bit = don't dither. I
would probably go further and say just use triangular dither, since at
some time in the future you may want to pitch the sound down (ie for a
sample library of drums with a tom you want to tune downwards, or
remixing a song) then any noise shaped dither will cause an issue
since the noise will become audible.
All the best,
Andrew
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