Subject:48 kHz / 24 bit Convert for CD - When/Where?

Posted by: agreatheight

Date:7/28/2005 10:53:31 PM

What is the best way to order the steps of mastering when working in 24 bit / 48 kHz in Sonar so that you can proper convert to 16 bit / 44.1 kHz?

I am running Sonar 4.0 as my DAW and I use SoundForge 8.0 for mastering, but this is my first project running 48 kHz and 24 bit in my DAW. Where and when should I convert (resampling and bit conversion) to redbook?

My general procedure is as follows: export, open in SoundForge, normalize, limit (UAD-1 Precision Limiter), look at frequency sprectrum, undo limit, undo normalize, apply EQ (UAD-1 Cambridge) based on what was seen and heard after normalization/limiting if necessary, normalize again, limit again. Whew...

Where is the best spot to resample/convert the project? I initially tried resampling/converting at the end of the sequence of events, but it caused clipping due to resampling (for sure), but not after the bit conversion (I think). Is that right?

I am thinking now about resampling after applying the eq (so the EQ processes at the highest sampling rate possible), before the second normalize and limiting, and running the bit conversion at that same time, or at the end of the process (if it causes no clipping). Or I could simply export 44.1 / 16 bit out of Sonar. What is best?

Any ideas / perspectives would be highly appreciated! I could be missing something very simple. Or maybe there is a better, completely different method or program or plug-in I should be looking at. Thanks!!

Subject:RE: 48 kHz / 24 bit Convert for CD - When/Where?

Reply by: mpd

Date:7/29/2005 7:11:03 AM

You want to resample and lower the bit depth as the last two steps in the chain (in the order).

How are you normalizing? Peaks or RMS? What settings?

Perosnally, I would use a different workflow.

I would use the plugin chainer and set it up like:

EQ -> Compress -> Limit

Ignore normalize. Use the EQ and Compress to get the sound you want, and then play with the Limiter to get the loudness you want. I am unfamiliar with the interface on those plugins, so you may need to add some Volumes into the chain to set the gain going into the limiter. Keep an eye on the meters and try to give yourself 0.5 dB headroom to prevent clipping in the final resample.

When this is done, resample to 44.1 and then lower the bit depth.

By using the plugin chainer, you can eliminate most of the undo steps, and it makes getting the sound you want a lot easier.

Subject:RE: 48 kHz / 24 bit Convert for CD - When/Where?

Reply by: agreatheight

Date:7/29/2005 10:48:11 PM

"You want to resample and lower the bit depth as the last two steps in the chain (in the order)."

Problem is when I use the SoundForge tools to resample and convert the bit depth at the end of the process, it causes clipping of my already limited tracks, anwhere from .1db all the way to .6db, which is obviously unacceptable.

Also, why shouldn't I normalize? I feel it gives me a better "picture" of the track and allows me to start with max volume when limiting.

Subject:RE: 48 kHz / 24 bit Convert for CD - When/Whe

Reply by: mpd

Date:7/30/2005 8:47:21 AM

Basically, you need some headroom during the resample step. Any filtering operation (including resampling) can result in increased peaks. If your limiter has an output control (sometimes called output headroom), set it to 0.5 dB or 1 dB. This will give you some headroom for the final resample. Using the 0 dBFS output from the limiter is only OK if that is your absoulte final output.

Personally, I work with VO. I leave myself about 6 dB headroom so I can make some pretty big volume adjustment if the producer / client wants them, without having to go back an reprocessing everything.

As for normalizing the peaks to 0 dBFS, it isn't really buying you anything. If you are going for loudness, then it can give you an idea of your starting point, but that's about it. Further processing may result in clipping. I really think that you will be happier if you ignore the normalize step, and use the plugin chainer to bounce back and forth between EQ and limiting, and use the input control on the limiter to drive it harder to get the loundess you want.

Subject:RE: 48 kHz / 24 bit Convert for CD - When/Where?

Reply by: Geoff_Wood

Date:7/31/2005 3:43:43 PM

SF8 ? Then you'd be using CDA5.2 ? That's where you can do it, using the built-in SRC and dither. Or if you want to use specific other SRC and dither, then do it in SF as the very last thing you do.


However, why not just use 44K1 fom the start in Sonar ?

geoff

Subject:RE: 48 kHz / 24 bit Convert for CD - When/Where?

Reply by: jumbuk

Date:7/31/2005 4:46:40 PM

"Why shouldn't I normalise?"

Not absolutely 100% sure on this, but I think:

- 24-bit is floating point, so you don't really get anything out of normalising, and

- any recalculation, including normalising, has the potential to introduce distortion (albeit very small), so why do it?

Subject:RE: 48 kHz / 24 bit Convert for CD - When/Whe

Reply by: airon0

Date:8/3/2005 2:36:26 AM

Almost. 32 bit floating point samples are the common processing format for VST(and DirectX?) plugins. That's what they output. I haven't seen any 24 bit float audio, and it's unlikely anyone will ever use it, because 32 bit float is being used already.

If you're keen on keeping all clean, do your processing as you normaly would, then switch off the limiter upon export to 32-bit Float WAV or 24 bit PCM WAV. Make shure there's a dB of headroom. Resample with something like Voxengo R8brain(free). Output to 32-bit float, as the Voxengo app can do that.

Then apply the limiter and your dither to that 44kHz/32 bit float audio.

Resampling already dithered audio may not be the best idea, since the dither and noiseshaping is taylored to work with the current sample rate.

Subject:RE: 48 kHz / 24 bit Convert for CD - When/Where?

Reply by: wymondham

Date:9/8/2005 11:55:21 AM

Hi agreatheight
Why are you not recording at 44.1 24 bit? The maths are easier than using 48.00 24bit? I'm recording at 24 bit but use 44.1
David.H