Bits rate and dithering in the Audio Montage?

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franciskimberley
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Bits rate and dithering in the Audio Montage?

Post by franciskimberley » Mon Feb 23, 2015 1:05 pm

Lots of the projects I'm getting are coming in at 24bit. I master at the same bit/sample rate in the Audio File view and then build the release in an Audio Montage and use that for the creation of all the different final formats. When burning a CD you dither down to 16bit, easy enough. When rendering for vinyl or an "HD" digital format I want to keep it at 24bit but I'm curious...:

The Audio Montage is a 32bit audio streamer. This means that it non-destructively upscales all audio used within it to 32bit, right? So, even though the audio used in the project is actually at 24bits, I would need to dither to 24bit if I wanted to render out at 24bit because of this upscale and subsequent truncation? And I would also need to dither to 16bit even if the original mixes and masters were at 16bit?

To be safe I've done it that way so far, and all the audio sounds the same after dithering as it does after mastering in the File View, but I'd rather not add noise if I don't have to.

Just out of interest, why is the montage a 32bit audio streamer? Why not have the audio dictate the bit rate like in the File View?

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Re: Bits rate and dithering in the Audio Montage?

Post by PG » Mon Feb 23, 2015 1:40 pm

Just out of interest, why is the montage a 32bit audio streamer? Why not have the audio dictate the bit rate like in the File View?
Because 99% of montages will process audio is some ways, at simply as leveling or fades, for instance. Hence 32 bit float is required.
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Re: Bits rate and dithering in the Audio Montage?

Post by franciskimberley » Mon Feb 23, 2015 4:35 pm

Thanks for the info PG, but the questions I really wanted answering were in the second paragraph.

"The Audio Montage is a 32bit audio streamer. This means that it non-destructively upscales all audio used within it to 32bit, right? So, even though the audio used in the project is actually at 24bits, I would need to dither to 24bit if I wanted to render out at 24bit because of this upscale and subsequent truncation? And I would also need to dither to 16bit even if the original mixes and masters were at 16bit?"

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Re: Bits rate and dithering in the Audio Montage?

Post by PG » Mon Feb 23, 2015 5:19 pm

"The Audio Montage is a 32bit audio streamer. This means that it non-destructively upscales all audio used within it to 32bit, right?
Right
So, even though the audio used in the project is actually at 24bits, I would need to dither to 24bit if I wanted to render out at 24bit because of this upscale and subsequent truncation?
Yes, as far as any processing is performed (levelling, fades, plugins), which is the case 99% of the time. But the process of going from 24 to 32 bit is lossless: going back to 24 bit does not need dithering if there is no processing, ie. if the samples are not changed.
And I would also need to dither to 16bit even if the original mixes and masters were at 16bit?"
Yes

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Re: Bits rate and dithering in the Audio Montage?

Post by franciskimberley » Mon Feb 23, 2015 5:25 pm

Thanks so much PG. Really really useful to know.

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Re: Bits rate and dithering in the Audio Montage?

Post by StudioCompyfox » Wed Dec 16, 2015 5:26 am

I know this is an old thread, but I haven't done this in quite a while. I'm on WL8.0.4 btw (not 7) - but the method is still the same.


Usually, I always Dither the output of the Audio Montage down to 16bit if I create a CUE/WAV sheet. Especially if I have 24bit or 32bit source files. Prior to WL7, I did have to check if my bitrates are all the same - not anymore, less troubles.


But the following thing is a bit tricky:
- the source files of the montage were already been mastered in 44/16 (I didn't do this, I'm just taking care of the proper CD authoring and DDP creation)
- if I render to DDP, the file size for a 45minute CD is as expected: 450MB. Opening the file as WAV from the DDP import (Montage) also reveals: 16bit
- creating a WAV/CUE sheet from the Audio Montage does result in a 32bit file however. I can't mount that file, neither can I I burn it with most tools.


Questions:
a) does the DDP file rendering from 44/16 source files with a safety limiter on one Master Rack slot need dithering down to 44/16 again? I didn't hear drastic damages so far. And as mentioned, the DDP file seems to be in proper 16bit post rendering.

b) would already 44/16bit dithered files not be "damaged" if I run another dither on top (example: CUE/WAV sheet creation, which would otherwise render 32bit WAV files)? I mean, it would definitely introduce more noise. Or does a normal bit-truncation work in this case?

c) would "burning" a CD (from the "Burn CD" button, which does create a CUE/WAV temp file) be bit-truncated? The WAV file created as temp is also 32bit. Yet it does burn to CD.


My main question is, if I need another general/safety Dithering instance or not.
And I am really confused right now.


Thanks for clearing that up on short notice.

Maybe also with a hint how to set up MBIT+ as transparent (re)dithering tool compared to the Apogee one, if dithering is really needed again.
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Re: Bits rate and dithering in the Audio Montage?

Post by bob99 » Wed Dec 16, 2015 5:49 am

StudioCompyfox wrote: b) would already 44/16bit dithered files not be "damaged" if I run another dither on top (example: CUE/WAV sheet creation, which would otherwise render 32bit WAV files)?
Just to answer one of the questions, if you're making a DDP from this same montage without dither, knowing the DDP process is making it 16 bit (which it always does), you could do the same for the CUE/WAV: force it to 16 bit in the CUE/WAV export file properties (that way it won't be 32bit). That is, if you're sure you don't need dither because the source files are 16 bit, and you're doing nothing (no gain, fades, edits, plugins) that would require further 16 bit dither. You don't need further dither if you're doing NO processing.

Play the files in the montage and look at the Bit Meter to see if only 16 bits are going through to the end of the chain for the entire program, and if so, don't dither to the CUE/WAV, and set the CUE/WAV render file properties to 16 bit, because that's how it's going to the DDP anyway if you're doing as I think you've described. But if you're doing any processing (gain, fades, edits, plugins), the DDP would need dither too, regardless of the fact that Wavelab's going to make the DDP 16 bit no matter what.

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Re: Bits rate and dithering in the Audio Montage?

Post by StudioCompyfox » Thu Dec 17, 2015 2:48 am

Looks like another Dithering step is inevitable, as I am indeed using a safety limiter (which in turn can result in new harmonics) and fade in/out (on the fly via the montage). The client provided material that was "limited to -0,1dBFS" - but it results in overs (up to +1dB), and of course no proper fade in/out.

So MBIT+ it is.


Thanks for the answer - really helpful.

Might be something for a manual update as "things to look out for".
Last edited by StudioCompyfox on Thu Dec 17, 2015 3:10 am, edited 1 time in total.
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Re: Bits rate and dithering in the Audio Montage?

Post by bob99 » Thu Dec 17, 2015 3:10 am

Yes, the CD and DDP would automatically truncate to 16 bit if you don't use dither. The CUE/WAV not so, which is why I would dither and force 44.1 16bit in the CUE/WAV render file properties. And dither for the CD and DDP.
Some programs can only read 16 bit CUE/WAV, but most of the audiophile programs can deal with 96K 24 bit or even 32 bit float CUE/WAV. I tested many of them a while ago, thinking that might be a great step above DDP for a hi-res "image" file. But commercial hi-res files are individual track files anyway (except Blu-Ray audio I think), so that's what's normally ordered.

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