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[jason levy]

Hello,

For a video project where the original source files are  16 bit, (at 48 ) does it make more sense to edit and mix in 16 bit (via software) or to upconvert everything to 24 bit and dither it back down to 16 after bouncing to disk?

Thanks

Jason

[Level]

All my DVD's are 24 bit in audio. For that, I see no reason to go back to 16 bit...however, if it started at 16 bit to end up at 16 bit, audio editing advantages of going to 24 bit may not outweigh the disadvantages of going back to 16 and adding dither.

To each his own. Try both ways and see for yourself. Your software may provide some surprises.

[henchman]

If it's a video project, it will likely end up on Digibeta which is 16 bit anyway.

So, yes, just stick with 16bit.

[bobkatz]

jason levy wrote on Sun, 03 April 2005 08:14

Hello, For a video project where the original source files are  16 bit, (at 48 ) does it make more sense to edit and mix in 16 bit (via software) or to upconvert everything to 24 bit and dither it back down to 16 after bouncing to disk? Thanks Jason

As soon as you mix, changing gain or other processing in the mixer, the output of the mixer will be the wordlength of the DSP, it will be LONGER than 16 bits. If it's a native system, it is likely to be 32 bit float. You should not have to convert your source files to longer wordlength, but yes you will have to save the output as 24 bit or dither it down prior to saving. In fact, if it's a native system, you really should dither it DOWN to 24 before saving it as 24 bits, to avoid the small quantization distortion from the 32 to 24 bit conversion.

BK

[henchman]

But if it is a native system, and the final is 16 bit, won't bouncing the final to 16 bit already apply dithering?

[bobkatz]

henchman wrote on Sun, 03 April 2005 10:26

If it's a video project, it will likely end up on Digibeta which is 16 bit anyway. So, yes, just stick with 16bit.

Unfortunately, both statements are incorrect.

#1. Digibeta (Digital Betacam) contains 4 channels of 20 bit audio, at 48 kHz sampling.

#2. Even if you start with 16 bit files, as soon as you put them through the DSP/mixer, your wordlength will grow. So, if you are going to put them down to a Digibeta, after mixing, they will have to be dithered DOWN to 20 bit.

Ironic, start with 16 bit, and you end up having to dither DOWN to 20... all part of the way digital audio works.

BK

[henchman]

Yes, this is true that the Digibeta's have 20 bit cahnenls. Howvere most post-transfer house require DA-88's for laybacks.

I think the big problem with the original question is that there is not enough info.

Just saying it is a video project is not enough.

What's the delivery format, and where will it end up.
What kind of video project is it?

[wwittman]

Quote:

all part of the way digital audio works.

If one can say digital recording ever "works" {g}

one learns to lessen one's expectations.

[jason levy]

Thanks everyone for the input.

The original audio was recorded on Panasonic DVC pro 50 vtrs. It is then captured to to 16 bit 48k files in a Final Cut Pro system via SDI with embedded audio using a Decklink card. (www.decklink.com). All that is out of my hands. (We also get material that originates on Betacam SP analog, also captured on a digibeta deck (reads the SP as well) via SDI with embedded audio)

I receive the audio as an OMF file. 16 bits 48k. I edit and mix and must deliver an SDII (or AIFF) file that is laid back to Digibeta via Final Cut Pro and a Decklink card, via SDI embedded audio.

I notice that final cut will accept 24 bit files but I don't know if it plays them natively or does some kind of conversion on the fly. We do need to make DA88s of the stems as well as a mix.

The system we work on is based on Digital Performer software, running on a macintosh computer. Digital Performer will run in either 16 or 24 bit mode.

Again thank you everyone for your comments. They are appreciated. If there is anything I have left out I would be happy to supply that information.

Bob thanks for the comments. Just got your book on mastering and am trying to plow through it.

Jason Levy

[Level]

What is the delivery (final) format?

If it is DVD, go to 24 bits and stay there.

[jason levy]

Final Deliver format - Digital Betacam.

Jason

[henchman]

jason levy wrote on Sun, 03 April 2005 13:41

We do need to make DA88s of the stems as well as a mix. Jason Levy

Save yourself the hassle. keep it 16 bit.
There's absolutely no reason to waste time fileconverting back and forth.

By the time this hits the airwaves, the broadcaster will have screwed with it enough that you could do it at 8-bit, and most people couldn't tell the difference.

[bobkatz]

jason levy wrote on Sun, 03 April 2005 13:41

I receive the audio as an OMF file. 16 bits 48k. I edit and mix and must deliver an SDII (or AIFF) file that is laid back to Digibeta via Final Cut Pro and a Decklink card, via SDI embedded audio.

Assuming that the Digibeta is the final master, then if you dither your AIFF files to 20 bit in a 24 bit file, it will be fine. The Digibeta will truncate the bottom four bits, but you already predithered it.

Final Cut will work with the 24 bit files and if they don't change gain or EQ within Final cut, then your predithering to 20 bit will hold. I'm not sure which plugin that you can get for performer will dither to 20 bits, I suspect the Waves L2 will do it.

However, never turn your back on digital. If you can convince the video house to get a bitscope it would be nice.

BK

[henchman]

But why would you waste the time and effort?

Seriously, converting everything to 24 bits, for Broadcast post is a waste of time.
You just won't hear it. We're not talkign high quality classical recordings here.

You'll usually be dealing with medicore location sound.
We do everything at 16 bit 48k.
99% of the SFX libraries are at 16 bit.

The conversion thing really is a waste of time IMO.

[Joel Silverman]

henchman wrote on Sun, 03 April 2005 15:41

You'll usually be dealing with medicore location sound.

and what about the VO being submitted to you as MP3s