MOTUNATION (formerly UnicorNation) is an independent community for discussing Digital Performer and other MOTU audio software and hardware. It is not affiliated with MOTU.
Forum rules
This forum is for seeking solutions to technical problems involving Digital Performer and/or plug-ins on MacOS, as well as feature requests, criticisms, comparison to other DAWs.
Didn't find answers with search or maybe I was too lazy...
Anyway, two questions:
1. Dither
When does Digital Performer use its own dither (Audio menu > Dither)?
Is it only when using Audio plugins (not real time, Audio menu > Audio plug-ins) or also while Bouncing the disk (24bit to 16bit)? If I have e.g. a L2 in the master fader, L2's dither set ON and I'm bouncing my 24bit project to 16bit: Can I be sure that DP does not add double dithering? My ears say it doesn't, but does anyone know is this really the truth?
2. External clock with Bounce to disk
Can DP benefit from using better external clock while Bouncing to disk?
1. Dither
When does Digital Performer use its own dither (Audio menu > Dither)?
Dither under the Audio menu is for non-MAS audio processing. This includes crossfades and printed audio effects. Generally, leave this on.
Is it only when using Audio plugins (not real time, Audio menu > Audio plug-ins) or also while Bouncing the disk (24bit to 16bit)? If I have e.g. a L2 in the master fader, L2's dither set ON and I'm bouncing my 24bit project to 16bit: Can I be sure that DP does not add double dithering? My ears say it doesn't, but does anyone know is this really the truth?
Checking Dither under the Audio menu does not add dither during bounce to disk.
2. External clock with Bounce to disk
Can DP benefit from using better external clock while Bouncing to disk?
No. Bounce to disk does not involve the audio interface. Clock makes a difference when recording or playing back.
Is it only when using Audio plugins (not real time, Audio menu > Audio plug-ins) or also while Bouncing the disk (24bit to 16bit)? If I have e.g. a L2 in the master fader, L2's dither set ON and I'm bouncing my 24bit project to 16bit: Can I be sure that DP does not add double dithering? My ears say it doesn't, but does anyone know is this really the truth?
Checking Dither under the Audio menu does not add dither during bounce to disk.
Magic Dave
Hi MagicD,
What should we do exactly to properly apply dithering in DP while bouncing a 24-bit session mix with 16-bit option selected ?
Do we need to use in conjunction the MW Limiter or any 3rd party mastering plug-in on the Master Bus with 16-bit dithering enabled (and noise shaping too, I guess ) ?
If yes, is it possible to make it Post Fader as I've heard that fade out automation on Master Bus occuring after dithering could lead to serious problems (peak overloads...)
And is there any dithering applied to a 24-bit soundbite when exporting to Aiff/Wav format with 16-bit option selected ?
Btw, is it more preferable (sound wise) to apply 16-bit dithering/noise shaping on a 24-bit mix prior to any mp3/aac conversion or could it be safely done directly within DP (actually only mp3) without any side effect and sound degradation ?
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)
Back to Top
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.
Back to Top
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.
Back to Top
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.
Back to Top
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.
Back to Top
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.
