Dither Question

[Julia123]

I have a project I mixed in Ableton. I am going to transfer it to DP and use Ozone to 'Master' it. Would it be best to export a 32 bit 48Hz undithered Wave file out of Ableton and import into DP? Next, should I use Ozone to dither when I export the final Wav (I hear the hype it's great), or DP and to what final format just for general use? I think I heard some odd dither effects in an Ozone dither test I ran but I really can't say what I was hearing for sure. I've always used DP's dither up until now (and just mixed all in DP) and never noticed it before, nor has anyone with better ears ever commented that my DP dither was bad I Trust you guys best. I've been over at the Ableton forum since I've been using it for some things---geeze--I don't want to say anything negative but no comparison!!! Thanks.

[FMiguelez]

Hi, Julia.

Dither is used when you reduce the bit depth of the audio to mask the quantising distortion.
You didn't specify the settings you used in Ableton Live's session. If it works as DP, with 32 bit floating point math, and you used 48 KHz as your sampling rate, then I'd take it out of Ableton with those same settings.
So you'd have a "Final Mix" out of Live printed as 32 bits and 48 KHz, probably WAV or AIFF.
Once your final mix is in DP (make sure DP is set exactly like that too, with no auto conversions ), master it away.
To print your master, you'd need to know what delivery format you need. I usually print my masters to 24/44.1, 16/44.1, mp3 and AAC (set to high-resolution). I bounce all these formats from this DP session (simply change your bounce settings as needed).
You would, of course, use dither as your last plug-in for the first two formats. For the last 2, you probably don't need dither, since it's a different process, but I'm not sure about it. Hopefully someone else can confirm if you need dither for mp3 or AAC, which I doubt.

Mind that, if you used 48 KHz as your sampling rate, you probably will need to convert it down to 44,1 for some media delivery (CD), and this adds a layer of complication, since you want to make sure this conversion is as transparent as possible with the least amount of artefacts. I've done this with DP, and it works great.
Let me try to find a recent thread, where I asked about exactly this sampling rate conversion issue, as well as the best way and order to do it ...

Hopefully this helps.

[FMiguelez]

http://www.motunation.com/forum/viewtop ... 2&p=506093

It's a little different in your case, since I already had the 24-bit masters printed in that example. If I were you, I'd change the sampling rate in DP (in case you need to deliver it with a 44,1 sampling rate) . I'd setup DP to 32 bits FP/44.1, then activate automatic conversions when the SR changes. Import it and let DP do its thing. Once it's been converted, master and dither from that, according to whatever you need.

OR, simply master them at the current SR, and do the SR conversion later, as the last step. I'm not sure what's best, in this particular case.

[Julia123]

Thanks, this helps immensely. Ableton is 32 bit so I can export that.

You would, of course, use dither as your last plug-in for the first two formats.

So if I bounce from 32 down to 48 & 44.1 and decide to use DP's dither from bounce, I should assume it will automatically add it as long as I have it checked? I was previously exporting from the soundbites list.

If I were you, I'd change the sampling rate in DP (in case you need to deliver it with a 44,1 sampling rate) . I'd setup DP to 32 bits FP/44.1, then activate automatic conversions when the SR changes. Import it and let DP do its thing. Once it's been converted, master and dither from that, according to whatever you need.

I think this is what I was probably hearing with my bad Ozone test, I didn't down sample first. When I've used DP, I down sampled 48 to 44.1 from their soundbites window and I'm guessing DP is smart enough to know what order to do this. Big lesson there! Also I didn't pay attention to the auto conversions in the past, I will now! I'm going to run a quick dither comparison of DP vs Ozone while doing this correctly and see what I get just out of curiosity. Thanks so much!

[stubbsonic]

Hopefully, I won't muddy the waters here.

I'd suggest you look at what the file format is for the mix you've produced in Ableton, and confirm the actual specs of the audio file itself.

If the actual file format is 24-bit, (or even 16-bit) it obviously won't matter what you "export as". You wouldn't gain anything by upsampling or upping bit depth of the file. But it might be worthwhile to re-render your mix at 24-bit and 48K (or higher).

BTW, I've found DP's sample-rate conversion (SRC) to be quite good.

I'd suggest making your mp3's and AAC's from the 16 bit versions. Though it is possible to have 24-bit mp3 and AAC's, I've had problems in the past with some players not working with them. I expect the 24-bit mp3's probably sound better, but I'm not sure what the rules are.

I always use fixed rate mp3s, at 320 kbps. But I'm curious if others like using VBR (variable bit-rate). I always used Normal Stereo, and not "Joint Stereo".

[FMiguelez]

I'd suggest you look at what the file format is for the mix you've produced in Ableton, and confirm the actual specs of the audio file itself.

If the actual file format is 24-bit, (or even 16-bit) it obviously won't matter what you "export as". You wouldn't gain anything by upsampling or upping bit depth of the file. But it might be worthwhile to re-render your mix at 24-bit and 48K (or higher).

Yes. I could've been clearer.
She won't gain anything by changing the bit depth of the individual audio files in her Ableton project. But she would gain resolution if she bounces or renders the final mix at whatever Ableton works. If it's like DP, which processes internally everything at 32 bits FP, then her final mix (the summing of all her tracks and FXs) would benefit from staying at that same word length (not truncating from 32 bit FP to 24 (or 16) bits).

I'd suggest making your mp3's and AAC's from the 16 bit versions. Though it is possible to have 24-bit mp3 and AAC's, I've had problems in the past with some players not working with them. I expect the 24-bit mp3's probably sound better, but I'm not sure what the rules are.

I always use fixed rate mp3s, at 320 kbps. But I'm curious if others like using VBR (variable bit-rate). I always used Normal Stereo, and not "Joint Stereo".

I use only fixed rate too.
What I am REALLY wondering now, is bouncing a master in AAC or mp3 format... If you have as your last plug-in in the mastering chain something like Waves' L2, which it forces you to quantise to 24 bits with or without dither, what happens with these formats?
Do they even need to be dithered?
And if not, what should one do with the IDR part of the L2? Just shut it down? I ask because I think it would still truncate from 32 bFP to 24 bits, without dither, if one turns it off...

So, how would one handle this situation for AAC and mp3 files? I think I've been doing it wrong, because I always get my masters from the same session, and simply change the formats in the BTD dialog box as needed, without regard for this issue. Hmmmm....

[FMiguelez]

Thanks, this helps immensely. Ableton is 32 bit so I can export that.

You would, of course, use dither as your last plug-in for the first two formats.

So if I bounce from 32 down to 48 & 44.1 and decide to use DP's dither from bounce, I should assume it will automatically add it as long as I have it checked? I was previously exporting from the soundbites list.

I think you're confusing those parameters.
32 bits FP refers to the bit depth of the project for processing, and it will use that same setting for new audio recordings. This is what DP uses natively to process audio and effects, independently of the same setting for the session audio files. You have the choice to record/import audio files as 32, 24 or 16 bits.

44.1 or 48 KHz refer to the sample rate.

You only dither when you reduce the bit depth of your audio, at the very last step, i.e., if you're bouncing down from 32 bFP (DP's native processing) to 24 or 16 bits.
But if you BOUNCE to Disk, in DP, and you need dither, you must add a dither plugin in the last insert. The Dither option under the Audio menu DOES NOT dither when bouncing (it only uses it for other processes, but not BTD).

If I were you, I'd change the sampling rate in DP (in case you need to deliver it with a 44,1 sampling rate) . I'd setup DP to 32 bits FP/44.1, then activate automatic conversions when the SR changes. Import it and let DP do its thing. Once it's been converted, master and dither from that, according to whatever you need.

I think this is what I was probably hearing with my bad Ozone test, I didn't down sample first. When I've used DP, I down sampled 48 to 44.1 from their soundbites window and I'm guessing DP is smart enough to know what order to do this. Big lesson there! Also I didn't pay attention to the auto conversions in the past, I will now! I'm going to run a quick dither comparison of DP vs Ozone while doing this correctly and see what I get just out of curiosity. Thanks so much!

My advise would be to, first of all, have a clear picture of the needed formats for whatever delivery medium you use.
Will it be for a CD release? Or will it only be to sell it in iTunes?
Each medium will need different formats. You might not need to downsample from 48 to 44.1 if you won't release a CD, for instance.

Either way, to downsample from 48 to 44.1, you have 2 choices. You master everything normally and downsample "the master", or you downsample your final mix first, and master from that resulting file. I am not quite sure about which is the most transparent of the two.

[Julia123]

Stubsonic: The Ableton was exported and saved at 32 bit 48K and works at 32 bit like DP. Thanks for the info.

So if I bounce from 32 down to 48 & 44.1 and decide to use DP's dither from bounce, I should assume it will automatically add it as long as I have it checked? I was previously exporting from the soundbites list.

I think you're confusing those parameters.

Whoops, I meant to say from 32 to 24 & 16, sorry. I checked the manual and it did say that when Dither is checked it does add it when bouncing a mix to disc.

[FMiguelez]

So if I bounce from 32 down to 48 & 44.1 and decide to use DP's dither from bounce, I should assume it will automatically add it as long as I have it checked? I was previously exporting from the soundbites list.

I think you're confusing those parameters.

Whoops, I meant to say from 32 to 24 & 16, sorry. I checked the manual and it did say that when Dither is checked it does add it when bouncing a mix to disc.

The manual is wrong!

Seriously. At least in that instance
It's been an old error that has never been corrected.

MagicDave made a post, long ago, telling us about that Dither command in the menus. I think it's for things like merging, creating new soundbites, etc, but NOT for bouncing (despite what the manual wrongly claims)

[FMiguelez]

There's a more complete description of this Dither command situation by Magic Dave, but I can't find it...

http://www.motunation.com/forum/viewtop ... 515#p50834

[FMiguelez]

I only found a reference to it, but not the original...
From:
http://www.motunation.com/forum/viewtop ... 853#p50853

1. Insert the MW limiter in the last plug in slot on your Master fader

In DP 2.7 or earlier, you would also want the fader at unity gain.In DP3, you can change the position of channel inserts to post fader (they were originally pre fader). There's a little handle at the bottom of the channel inserts. If you drag this up, inserts below that handle are now post fader. That means you could change the fader level and you would be adjusting signal going into the limiter, as opposed to changing the output level of the limiter.

2. Make that insert slot Post Fader (DP 3 only)

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3. In the MW limiter, choose 16 bit (Quantization)

When you go from a higher bit depth to a lower bit depth, what you don't want to do is just chop off the bottom bits. If you make a 24 bit sample into a 16 bit sample by losing the bottom 8 bits, that's called truncation and you are losing any info in those bottom bits. The better way to do it is to quantize the higher number to a lower number. Essentially you are rounding off the bottom 8 bits into the next 3 or 4 bits above that. In other words, the resulting 16 bits contain a rounded version of the former 24 bit sample and that rounding ended up in the bottom 3 or 4 bits of the 16 bit sample. An unfortunate side effect of bit rounding is distortion of signals that occupy those rounded bits. It's important to understand that quantization only effects the bottom of the sample and therefore only effects very soft signals that are represented by those bottom bits. A loud signal that lives in the top of the sample is not affected by the quantization.

The MW limiter works at 64 bit float. It then rounds down to 32 bit float for output into the MAS signal path. MAS rounds down to 24 bit fixed integer for output to D/A converter and print to file.

However, notice the little button in the bottom left hand corner of the MW Limiter? Bit quantization is always on in this plug. The maximum bit quantization is 24 bits. That means that even though the sample outputting from the MW limiter is 32 bits, the sample has been quantized into the top 24 bits. The whole point of the limiter is to do exactly that, limit the top end of the signal. The MW limiter does not add any gain. It can't. And what it will do is limit any input signal to 24 fixed bits.

When rounding from floating point to fixed integer, dither is not required.

I always have a Limiter on a master fader when I work in DP. I usually set the limiter to 24 bit while I'm tracking, then drop to 16 bit as I start to mix. If you just want to forget about it, leave it at 16 bit.

If you are not doing your own mastering, it is very much desirable to provide a 24 bit file to the mastering house. Obviously for that you would leave the Limiter at 24 bit and BTD at 24 bit.

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4. Dither is optional. Noiseshaping is a sub option of Dither

Dither is the process of randomizing the bottom bits. This randomization produces noise. Dither is noise. This process obscures quantization distortion. If you had a signal that was suffering from quantization distortion, applying dither would soften the distortion but introduce low level noise to the audio.

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Noiseshaping is a variation of the randomization and the result is a different spectral shape of the dither noise. Think of it as the difference between white and pink noise. There's no mystery as to what dither noise sounds like. Set the quantization of the MW Limiter to 4 or 6 bits. Now turn on dither. You will hear the dither noise. Select noise shaping. Now you hear the difference in the frequency curve of the dither noise. When you go from a higher bit depth to a lower bit depth, you should always quantize. Dithering however, should be considered an option, not a requirement. Dithering should be applied if the program material benefits from it. Noiseshaping should be selected based on what you hear (and prefer). One example of when I would not use dither is highly compressed rock music. If the tracks are just loud all the way through, you may never be using the bottom bits of the sample. Adding dither would only introduce noise and would not fix any distortion.

The time to be picky about dither and noiseshaping is when you have an audio track with a wide dynamic range. The best example to illustrate this is a single piano note. As the note decays, it uses lower and lower bits in the sample. When the note gets into the bottom 3 bits of a quantized 16 bit sample, you'll hear the quantization distortion. If you add dither, you won't get the distortion but you will hear low level noise (kinda like tape hiss). You make the choice as to the noise shape curve.

If you care about these subjects you should do basic tests like recording a piano note so you actually hear what these processes do. Just following rules about how to engineer won't get you good sounds. The experience of actually hearing the difference gives you the expertise to make an educated decision about what processes you should use.

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5. Choose 16 bits from the Bounce to disk window

Choosing 16 bit in BTD means that DP writes a 16 bit file. Since the output of DP is always 24 bit, a 16 bit BTD just truncates the last 8 bits. You want to make sure there is no useful information in those last 8 bits before you BTD. That's where the MW Limiter comes in. The output of the master fader to D/A converter or file is always 24 bit. If the Limiter is used and set to quantize to 16 bits, the output to file or D/A converter is still 24 bit, but the last 8 bits are now zeroed out. They no longer contain audio data. What had been 24 bits of info has now been rounded into the top 16 bits. That means that when BTD truncates the bottom 8 bits, it's OK because there's no data in those bits.

When you choose the output for a bounce, DP is rounding to 24 bit fixed. If the bounce is to 24 bit, you get all 24 bits. If the bounce is to 16 bit, the bottom 8 bits are truncated by the bounce process. That's why you should use the MW limiter to quantize to 16 bits, even if your source files are 16 bits.

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6. Dither option under the Audio menu does nothing when you BTD

When you bounce to disk, the Dither option under the Audio menu does nothing.

There's been lots of talk about what the Dither option under the Audio menu does. I asked The Person Who Knows and got this reply:

Dither under the Audio menu is applied when DP creates an audio file. There is a difference between DP creating an audio file or that audio file being created by MAS. For example, recording, rerecording, or bouncing is a MAS function. Pitch shifting, creating crossfades, printing a destructive effect, or merging audio are all DP functions. When DP creates an audio file directly, it is going from the floating point number to either a 16 bit or 24 bit fixed integer sample. Rounding happens automatically. The only difference between the dither in the Audio menu and the dither in the MW Limiter is that the Audio menu dither doesn't have the sub-option of noiseshaping.

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-Magic Dave

[Julia123]

The manual is wrong!

Seriously. At least in that instance
It's been an old error that has never been corrected.

Holy Cr**! So that's why the dither was unnoticeable Thanks for posting the dither info by Dave.

[Phil O]

Regarding SRC: iZotope supposedly has some of the best SRC on the market (some comparisons here: http://src.infinitewave.ca/). I'm using Ozone 6 and the stand-alone version has SRC. Simply export an audio file and if you select a lower sample rate than the original file it does it automatically. I rarely need SRC, but when I do I use Ozone. Ive also been using it for dither when mastering, but I use the Ozone plug-in in DP for that. It has several dither options, so you can listen before you bounce and select the option that sounds best.

Phil

[Julia123]

Thanks for the info on Ozone's rep and link. I've been too busy to dig in and analyze/compare this but I intend to. I have a follow up question. Looking at the manual, I can't tell whether when you convert the bit down to 16 from 24 or 32 within the soundbites menu, if it automatically dithers if you have it checked. I'm not sure if this is different than when bouncing. Even if the manual did say one way or the other, I'm thinking I better double check!!

[Nibiru]

Thanks for the info on Ozone's rep and link. I've been too busy to dig in and analyze/compare this but I intend to. I have a follow up question. Looking at the manual, I can't tell whether when you convert the bit down to 16 from 24 or 32 within the soundbites menu, if it automatically dithers if you have it checked. I'm not sure if this is different than when bouncing. Even if the manual did say one way or the other, I'm thinking I better double check!!

Hey all.

From what I gather from the Magic Dave post, is that no noise shaping happens when converting from the Soundbites window, only truncating. Noise shaping happens when bouncing to disk, if you so chose to have that option selected within your limiter plugin. Correct?

My question is...what does one do when recording via sends on an Aux (2bus) to a stereo track, live? My projects are at 32bfp/44.1. Would setting the limiter plugin at 24bit, recording said song, then converting from 32 to 24, be the same as bouncing to disk? I've never been a BTD guy since DP6 and haven't looked back. Am I missing something?