32float to 24fixed DEFINITIVE THREAD

Heylow everybody.



My question will be simple : In a floating point based DAW (mine is Sonar)

Should we use dithering on a 32-bit float mix down file (during mastering process) when we want (to export) a 24-bit mastered file?





First, we got a positive answer to this question

Quote:

Hermetech Mastering Forgetting about later conversion to lossy formats, I always dither 32 bit float to 24 bit before: A) Leaving the digital chain and sending the signal out of a DAC (either to the analogue chain or the monitors). My interface and converters only work at 24 bit. B) Rendering the final client file (if they have asked for 24 bit). I can hear a difference when I take the dither off. Yes, it's subjective, and theoretically below the noise floor, but I swear it sounds better with it on. Bob Katz recommends this in both his books, and Bob Olhsson has often stated on here and on other forums that he can hear the difference. I'm patiently waiting for Sonoris Dither to be updated with a 24 bit dither, so I don't have to keep slapping on an Elephant just for the dither when leaving the digital chain...

Then, we have a kind of "yes/no" answer to this question

Quote:

dkatz42 Going from 32 float to 24 fixed is NOT truncating; there are only 24 data bits in the 32 bit float. If the signal is at a lower level but actually has 24 bits of content (say, a fader is pulled down), low order bits will be lost in the conversion, but those bits would be thrown away at the DAC anyhow, which is a 24 fixed device. It's easy to demonstrate that you will end up with *exactly* the SAME bits going to the DAC in either case. As I said earlier, the value in 32 bit floats are in dynamic range, not in resolution (other than a marginal improvement in roundoff error when doing lots of intermediate calculations.) The other issue is that the bottom three or four bits in a 24 bit sample are garbage anyhow, as the converters simply aren't accurate enough to put something useful there. This means that dithering beyond 24 data bits, assuming that you had them (which you don't) is essentially fruitless. The 24/16 conversion is a different animal, because it *is* very lossy, and dithering provides a way of preserving a couple of bits beyond the 16 in a statistical way.

And another still interesting kind of "yes/no" answer to this question

Quote:

Lawrence The *only* benefit I can see using 32-bit float files anytime is maybe *rendering* (and only rendering, if it leaves the converters or hit any digital I/O pipe it'll be truncated to 24 again) a 32-bit float in-the-box final mix file. What this does is keep the daw from truncating your mix to 24-bits. It is *subjectively and theoretically* useful if you plan on doing more dsp processes later in a mastering app like Wavelab or Sound Forge (or the same daw) which I think also operate as 32-bit float internally. In this case you won't be applying more dsp to a file that's already been truncated. Some (like me) choose instead to just add 24-bit dither at the mix bus (with no noise shaping) and render 24-bit mix files, with the dither (theoretically & subjectively) minimizing the effect of the truncation from 32-bit float to 24. Most do neither. There's much debate about how many times a file has to be truncated before you actually start to hear it. I think it's probably many, many times in most cases. IMHO recording 32-bit float tracks is a waste of hard disk space

Finaly, we got a negative answer to this question

Quote:

FabienTDR Dithering is a super cheap process, there aren't many reasons why a dev would ignore dithering. BUT, one of them is a floating point environment, where the whole theory of dithering doesn't make any sense. There's no way or true need to "dither" floating point data (it's not dither in this case, it's pure damage). This applies to all modern floating point based DAWs. Reason, too. Be suspicious when you see a dither option in a floating point environment, it's straight bullshit. - Dithering is a pure fixed point concept that can ONLY be added in a TRUE fixed point environment, with fixed point math. The problem with reason is uncontrolled bandwidth extension "by design".

The question could also be read as : whether adding dither is compromising the quality of conversion, compared to just a "truncated" 32float to 24fixed file.

Now, as noobs (who want to learn and being able to provide the best material to listeners), you'll certainly understand why we still ask this question.

Thank you for your answers

32float to 24fixed DEFINITIVE THREAD