Dithering to 24 bit question (64 bit plugins/DAW)

[aleatoric]

Let me see if I understand this correctly.

When I am working with 24 bit source files and using 64 bit precision plugins (in a 48 bit or 64 bit DAW) I should apply a flat 24 bit dither (no noise shaping) at the end of my chain right? I always bounce processed 24 bit source files to 24 bit and only apply 16 bit noise shaping dither in my assembly DAW (WaveBurner) after any SRC or fades . My understanding is that in this situation I should be applying a flat 24 bit dither when bouncing to 24 bits. However if my final target medium was 24 bits (for DVD audio or archival purposes) I would then use a 24 bit noise shaping dither. Is that making sense? Also, yes I know this is a very minor detail in the grand scheme of things but none the less I would like to confirm that I am indeed doing this "correctly". Thanks.

[aleatoric]

No one huh?

[the unik]

mmm...When bouncing, that may be correct, though I think it's already done by the plugin itself, processing internaly at 64 bit and resulting in a 24 bits output, not sure though, it may depend on the plugin actually...

AFAIC I don't bounce, just record back the track in realtime into the daw.

Originally Posted by aleatoric

Let me see if I understand this correctly.

When I am working with 24 bit source files and using 64 bit precision plugins (in a 48 bit or 64 bit DAW) I should apply a flat 24 bit dither (no noise shaping) at the end of my chain right? I always bounce processed 24 bit source files to 24 bit and only apply 16 bit noise shaping dither in my assembly DAW (WaveBurner) after any SRC or fades . My understanding is that in this situation I should be applying a flat 24 bit dither when bouncing to 24 bits. However if my final target medium was 24 bits (for DVD audio or archival purposes) I would then use a 24 bit noise shaping dither. Is that making sense? Also, yes I know this is a very minor detail in the grand scheme of things but none the less I would like to confirm that I am indeed doing this "correctly". Thanks.

[CZ101]

Originally Posted by aleatoric

Let me see if I understand this correctly.

When I am working with 24 bit source files and using 64 bit precision plugins (in a 48 bit or 64 bit DAW) I should apply a flat 24 bit dither (no noise shaping) at the end of my chain right? I always bounce processed 24 bit source files to 24 bit and only apply 16 bit noise shaping dither in my assembly DAW (WaveBurner) after any SRC or fades . My understanding is that in this situation I should be applying a flat 24 bit dither when bouncing to 24 bits. However if my final target medium was 24 bits (for DVD audio or archival purposes) I would then use a 24 bit noise shaping dither. Is that making sense? Also, yes I know this is a very minor detail in the grand scheme of things but none the less I would like to confirm that I am indeed doing this "correctly". Thanks.

It depends on what's going on in your DAW..

If your DAW by default dithers from floating point or 48 bit back into 24-bit integer (which it should, either set by you or by design), then adding an additional dither stage (later or as a plugin on the DAW's output bus, etc), with or without noise shaping is redundant for a 24 bit target medium.

If your assembly program is WaveBurner, I'm assuming your DAW is Logic? If you're going 24 bit file to 64 bit fp process to 24 bit output from Logic (either D/A or bounced file), the conversion from 24 bits to 64 bits and back again dithers down automatically by default in Logic - this internal dither may or may not include noiseshaping (anyone know? either way, ns for >=32 bit floating point to 24 bit integer dither won't reaaally matter, imho).

So the "flat 24 bit dither" you speak of is probably already happening in your DAW, and maybe even w/ noiseshaping included in the process (internally, not sure)... Best to avoid having either of them happen subsequently - alone or together...

Anyone please correct me if I am wrong about this..

[Petrus]

Dither or no dither at 24 bits: the artefacts would be around -140 dBFS. With the best possible recording systems* the bottom 20-30 dB will be just noise anyway, so why bother polishing the bottom 6 dB of that pile of dust?

*)The very best converters get about 120 dB dynamic range, as do mic preamps. The last 3-4 bits are just random noise always, even if nominally using 24 bits.

[CZ101]

Originally Posted by Petrus

Dither or no dither at 24 bits: the artefacts would be around -140 dBFS. With the best possible recording systems* the bottom 20-30 dB will be just noise anyway, so why bother polishing the bottom 6 dB of that pile of dust?

*)The very best converters get about 120 dB dynamic range, as do mic preamps. The last 3-4 bits are just random noise always, even if nominally using 24 bits.

Well, if he's dithering from 24-bit to 24-bit then yes, the dither noise would be inaudible to most humans on most systems.. But it's unnecessary...

Also, most stuff these days will get dithered to 16 bit at some point, so although dithering 64 fp - 24 bit - 24 bit might not make that much of a difference, the extraneous 24 bit dither will become more audibly apparent when that file is dithered to 16 bit.

[Bob Olhsson]

My experience has been that failing to dither a 24 bit file can definitely come back around and bite you with crunchy sound upon subsequent processing.

The dithered 24 bit files should sound exactly the same or subtly smoother. Unfortunately sometimes 24 bit software dithering is broken so you always need to use your ears.

[CZ101]

Originally Posted by Bob Olhsson

My experience has been that failing to dither a 24 bit file can definitely come back around and bite you with crunchy sound upon subsequent processing.

The dithered 24 bit files should sound exactly the same or subtly smoother. Unfortunately sometimes 24 bit software dithering is broken so you always need to use your ears.

Interesting.. So you're saying that (let's just use Logic as an example) if you were bouncing to a 24 bit file from Logic, you'd still make sure that there be dithering (that you approved of, sonically) -to- 24 bits going on at the end of the chain.. If so, then I've learned something.

What about the possibility of that 24 bit file being dithered to 16 bit in the future? Would you still put it through 24 bit - 24 bit dither if you thought it might later end up as 16 bit?

[Coyoteous]

Not to answer for BO, but dither when you reduce word-length... simple as that.

I use flat TPDF, unless I know material will have not further processing... which is never.

[Bob Olhsson]

What dithering does is to randomize the bottom bit where the audio cuts off so that the truncation sounds like hiss rather than like distortion. The dither level always needs to be appropriate for the word length you are truncating to and some software developers have screwed this up.

Dither is not used to mask the distortion, it simply eliminates it provided it is done properly.

[cjac9]

Bob,
I'm mixing down in PTLE with a Waves L2 for dithering only. Should I use noise shaping, if so which profile? Moderate, Normal or Ultra?

Thanks,
cjac9

[UnderTow]

Originally Posted by cjac9

Bob,
I'm mixing down in PTLE with a Waves L2 for dithering only. Should I use noise shaping, if so which profile? Moderate, Normal or Ultra?

Thanks,
cjac9

If this is the final bit reduction to 16 bit, you can use shaping. Use yours ears to decide which one (if any). If you are going to 24 bit, no shaping.

Alistair

[Cellotron]

In my direct experience there's been no audible difference between the sound of truncating the sum of my DAW's 64bit processing to 24bit versus dithering the same to 24bit. Obviously OMMV! (and this may in fact depend on what processing you apply and what DAW app you use)

Best regards,
Steve Berson

[mr.farkendorfer]

Originally Posted by aleatoric

Let me see if I understand this correctly.

When I am working with 24 bit source files and using 64 bit precision plugins (in a 48 bit or 64 bit DAW) I should apply a flat 24 bit dither (no noise shaping) at the end of my chain right? I always bounce processed 24 bit source files to 24 bit and only apply 16 bit noise shaping dither in my assembly DAW (WaveBurner) after any SRC or fades . My understanding is that in this situation I should be applying a flat 24 bit dither when bouncing to 24 bits. However if my final target medium was 24 bits (for DVD audio or archival purposes) I would then use a 24 bit noise shaping dither. Is that making sense? Also, yes I know this is a very minor detail in the grand scheme of things but none the less I would like to confirm that I am indeed doing this "correctly". Thanks.

Hi,

What is the level of the analog noise floor [e.g. mic pres, hiss, pickup / amp hum, microphones, "component noise", ambient sound,......] in your material?

Is all that quieter than -96dBfs?

[aleatoric]

Originally Posted by Cellotron

In my direct experience there's been no audible difference between the sound of truncating the sum of my DAW's 64bit processing to 24bit versus dithering the same to 24bit.

+1. This is a somewhat older thread of mine. I have concluded that there is really no need to dither to 24 bits. In my listening tests it proves inaudible. That being said if the final delivery format intended for listening is 24 bits I will apply a noise shaping 24 bit dither. It certainly does not hurt. If anything there could be an audible benefit if DA converters ever started performing at a true 24 bit resolution (144dB dynamic range).

[Bob Olhsson]

I'd say it's more often than not inaudible however I've also gotten bit occasionally and for sure the dither is more inaudible if it's working right.

I use the L2 on moderate for 24 bit. or the others with no noise shaping for my mixes. I've occasionally sent pro tools mixes back for a re-bounce using the dithered mixer plug and gotten a less crunchy sounding master.

Samplitude is the only DAW application I've encountered that just handles dither properly and lots of folks say it sounds better. Pro Tools le sounds just as good to me with 24 bit dither using the same converters and monitor system.

[mr.farkendorfer]

Originally Posted by Bob Olhsson

I've occasionally sent pro tools mixes back for a re-bounce using the dithered mixer plug ....

And they bought it?

Not the whole mix, just the bounce?