Ripping HDCD in iTunes?

[Dusty Chalk]

Hmm. Coming from the visual world, I never thought this through. Let me see if I've got this straight..

In imaging, you've got n-number of steps between two absolute values - black and white, or some arbitrary ink coverage values that you're printer has chosen to represent them. If you have 8 bits, you have 256 usable steps; 16 bits and you have 64K-odd usable steps. (8 bits is generally fine for output, BTW, but doesn't have enough headroom to allow for much editing - editing used here in the sense of tonal manipulation).

If I'm hearing grawk right, in audio, only one end of the scale is fixed. You go down from 0db in steps that are fixed in size, rather than being proportional to some absolute value for "really very quiet". With a longer word length, you get a different value (in terms of energy, say) for your "really very quiet" value, and thus, if the "really very quiet" value is lower than the 80 or so db down that real gear can produce (or the 6 db down that pop recordings might have), then your longer word is wasted. The waveform drawn in the usable part of the dynamic range would come out identical either way.

Filbert? grawk? Is this what you're saying?

Okay, that was great, you definitely have a gift for putting things in a way that I can understand. (I'm still not sure I understand Dan's compatability comment, but I'm not going to ask him now, since he's probably drunk off his rocker. And I haven't gone off and tried to figure it out on my own yet.) Now do me...er...you know what I mean, translate what I was trying to say for Dan & co..

But...although I agree that when the "top" 16 bits are 0x0000 or 0x0001 (sticking with positive values), that the lower 8 bits would make no difference, it's when the values are 0x7FFF and so on that they would have a cumulative effect on the sound.

[grawk]

What I meant is that bits 1-16 are the same in 16 and 24 bit recordings. So as long as your content would fit in 96db, there is no difference between 16 and 24 bits. That way, you can play back a 24 bit recording using a 16 bit dac, and it will work just fine.

[Dusty Chalk]

(a) But that's a dynamic range thing.

( And in the real world, they'd be different. If they were both based on the same 24-bit master, the 16-bit redbook recording would have been dithered down to obscure the quantization error, whereas the 16-bit DAC with 24-bit input would probably just truncate it.

You know, I have a 16-bit DAC, that's something I can try on my own.

[grawk]

Right, but that's a decoding problem. You obviously apply dither on the last bit when converting from 24 to 16 bits. The format was written that way so as to be compatible, not to make it ideal.

[Dusty Chalk]

So why do you need dither if you can't hear the bottom-most bit?

[grawk]

You obviously can hear the bottom bits when the music is quiet, and ears are really good at picking up "wrong" even when it's very quiet. Dither exists to make the errors unobtrusive. Besides, I'm not arguing that 16 bits is more than you need. I'm arguing that 24 bits is more than you need, that 16 is enough. Plus, just because it's possible to master correctly for 16 bits, doesn't mean that everything being converted from 24 to 16 was mastered correctly.

Edited August 26, 2009 by grawk

[Dusty Chalk]

So you shouldn't need to dither 24-bit audio, then, right?

[grawk]

24bit audio doesn't need to be dithered when played back at 24 bits, right.

If you mean playing back 24 bit audio at 16 bit, then you definitely need to dither, unless it was mastered for 16 bit compatibility.

[Dusty Chalk]

No, I meant if you were, say, starting from a 32-bit master or something. So theoretically, if one was starting from a 24-bit master and listening in 20-bit, one wouldn't need dithering either? You could just truncate?

[grawk]

No, I'm not saying that. It all depends on the master. You'd want dither to prevent bit alignment errors in almost every situation. When you convert from higher bit depths to lower, you have to do soemthing to make sure there's no bit alignment errors from the conversion, and you want to make sure to remove excess headroom to make sure you don't lose data. If you have 80db of data, but leave 30db of headroom (reasonable when recording in 24bit), you need to move everything up, so you only leave 6db of headroom.

[Dusty Chalk]

You mean if the bits slip while entering the DAC? I guess that could happen. Do you really think they worry about that? Because there's no excuse for alignment errors during the downsampling process. And shouldn't that functionality be built into the DAC? (Arguably.) And yeah, there are other reasons which wouldn't directly effect the listening experience also, like DC offset (again, arguably -- not necessarily the responsibility of the author of the bitstream to alot for that, if the DAC was bullet proof [could handle any legal inputs]), but since it's so easy to accomodate for in the dithering process, why not?

I would suggest that the headroom argument could be rendered moot by putting criteria on the input -- assume all the headroom had already been taken up (with some entirely unrealistic hypothetical inaudible soft limiter, or by the mastering digitizer knowing his gear well enough to know exactly where to put levels). But both of those are relatively minor arguments.

So by the same token, you'd have to retract your stance on that would apply to 24-bits as well, neh? (In the downsampling from 32-bit example.)

[grawk]

We've gone so hypothetical that I can no longer follow what it is you're trying to say.

[Dusty Chalk]

32- or even 64-bit internal is not at all hypothetical.

[Pars]

Do you have any other HDCDs?

HDCD list - Head-Fi: Covering Headphones, Earphones and Portable Audio

Ahh, thanks. Going thru the list I didn't find much if any that I have. I did find Blondie Live, and looking at the jewel case, it was marked HDCD (even though it was a BMG pressing). Put it in, and once I hit play the HDCD light came on. Thanks, answered my question.

[The Monkey]

I ripped some this past weekend. Will try to light the light this week.

[deepak]

I ripped some this past weekend. Will try to light the light this week.

It's great. The little voice in your head goes "hell yeah son" when it comes on

[Sherwood]

I'm glad I'm not the only one whose little voice is Big Black from Rob and Big.