Logic thru Ozone 4... Dithering.

[charlie]

Hi,

I've read in past posts on the old LUG list that when it comes time to squeeze your masterpiece from 48k down to 44.1k for CD mastering, to use Logic Pro's built in dithering modes. (I am bouncing my 48k/24bit "mastered" track via Ozone 4 to a 44.1k/16bit stereo WAV file.)
I have been producing energetic electronic music lately and frankly, I can't tell the difference between Logic Pro's dithering and the two POW-r "noise shaping" formats provided. (Did I mention I use Logic Pro 7.2.3?)
Anyway, within Ozone 4, there is a Dithering pane in the mastering chain.
I notice that they have more "psycho-acoustic" shaping modes and a greater selection of options.

Now, I'm not sure if "more" means "better," but does anybody here
a) use Ozone for Dithering and/or,
b) think that these options make the end product sound better?

And one more question, how would one use Ozone to dither out of Logic as Ozone does not seem to let you select frequency (as in 48 or 44.1k...) but does let you select the bit rate & noise-shaping parameters. It would seem that one might set Logic to bounce down to 44.1k leaving the bit rate at 24. But does Ozone then "over ride" Logic on the output?
It's confusing.

Thanks in advance,
charlie eisenhardt

 

[Eli]

Hi Charlie,

While I can't really answer the bulk of your question, you should know that dithering and sample rate conversion are two separate processes. It seems like you might be confusing the two things.

Dithering is only applied to bit depth reduction. It is a mathematical algorithm used to intelligently calculate/reduce the bit depth instead of just lopping off the top eight bits of information. It's a means of interpolating that additional digital information and including some in the remaining 16 bits.

Sample rate conversion is different. It reduces the number of samples being used. But it doesn't actually alter the content of the samples themselves.

As far as Ozone - I don't have any info to add other than to say that if you do use the dithering in Ozone and choose _not_ do use Logic's dithering on the bounce down - you should be fine. The sample rate conversion is a separate process.

Hope this helps....

 

[charlie]

Thanks Eli, you're right... I have been a tad confused where the "dithering compression" takes place. -Your advice would make perfect sense then; change only the frequency in Logic for my final Bounce (from 48k to 44.1k) and let Ozone do the dithering/noise shaping...
I'll let you know if I hear any difference to Logic's three choices... ; )

Thanks!
I am still curious if anyone out there uses Ozone with any regularity and success.
I am happily learning from all my happy mistakes so, any information is appreciated.

Thanks!
Charlie

 

[Antiphones]

Eli is not 100% correct here, though right in pointing out that bit reduction and dithering are separate processes.

If your files in logic are 24 bit, when you bounce for CD as you know you need to move them to 16 bit. This truncation process causes distortion due to the fact that you cannot move 24 bits to 16 without rounding errors in the maths involved. Those rounding errors cause distortion which results in loss of detail, space and 3D depth in the music. In some type of music this may not be noticeable, in many type however it will definitely be noticeable.

Dithering is a process where a special kind of shaped noise is added to the signal to cover the rounding errors that occur during bit reduction. It literally gets rid of the rounding error distortion. The only tradeoff is that you get a bit of low level noise added to the signal. However this noise is acoustically shaped so that the human hear can hardly detect it. There are different ways you can shape this noise (ie the dither options in Ozone and other limiters), some noise shapes work better for some kinds of music than others. Its all a matter of subjective choice, there is no "right choice" when it comes to the type of dithering to use.

The general rule is never dither twice and always dither as the very last step. So don't dither until the final step of moving to 16 bit. Never dither and then reopen the dithered files and edit them. Never dither at one point in the signal chain and then again in another.

If you want to use Ozone or any limiter with dithering to dither your final 16 bit file make sure Ozone is the very last thing in the chain of effects on the output fade channel. Turn on its dither and then when you bounce, turn OFF logic's dither. But set logic's bounce to 16 bit. Doing it this way, Logic will move your 48k to 44.1k and 24 bit to 16 bit and use the dither noise added by Ozone to cover the rounding errors.

Having said that, Logic's dither noise is excellent, its the same one as used in Protools for example, so Logic users (for my money) don't need to use the dither features of plugins. If it were me, I'd use Ozone to eq/excite/compress/limit/ etc... turn off its dithering and use Logic to dither.

Hope this helps.

 

[midnightsun]

I just want to underscore the recommendation that dithering should be the final step. With many platforms whenever you digitally process a signal (even if you have dropped its bit rate) the bit rate jumps up so the final computation must be truncated or dithered again before going to 16 bit. There are many more sample rate conversion and dithering reduction programs out there than there are DAW platforms by along shot. People get in fist fights over which ones are the best. I recommend that you use which ever ones you own where workflow is the easiest until you have time to do a methodical A/B comparison for yourself.