Logic's Dither Questions

This is a 2 part, or even 3 part question. What dither settings do you use on your final finished mix for (A) .mp3 (B) .wav and © .anything else.

Last week I finished a project then bounced it just so I can do the mastering separately. I bounced it to .wav (no idea what dither). Should I have bounced it to AIFF?

I use Waves. They are always asking about dither. Should I use their dither? Is logics dither different? Is using a lot of waves plugs that have dither on/off effecting my sound?

Check out these two threads. Perhaps they will help you.

http://discussions.apple.com/thread.jspa?threadID=2339512&tstart=0

http://www.logicprohelp.com/viewtopic.php?t=56429

I agree with Kent. If you can't hear the differences, don't spend too much time agonizing over which algo you should choose (or whether you should choose one at all). However if you pick one you should only dither ONCE. So ONE wave plug-in, or Logic's dither, but don't dither several times.

Wave and Aiff sound exactly the same, if it's for you it doesn't matter, if it's for someone else, ask them what they prefer - but both should work exactly the same.

What dither settings do you use on your final finished mix for (A) .mp3 (B) .wav and © .anything else.

As already mentioned, the type of dither you choose will rarely be audible. So this is an academic discussion.

The reason you're using dither is to avoid the quantization noise that happens during straight truncation (simply throwing away bits when going from a high bit depth to a lower one). Most people won't be able to hear the noise under normal listening conditions. It sounds like digital distortion on low level signals. These artifacts can make the whole master sound a slightly more midrangy due to the psychoacoustics of distortion. Audible noise from truncation in a 24 bit file isn't an issue so I'm talking about straight truncation to 16 bits.

I often use POW-r #1 (colored dither) for most kinds of modern music. It's slighty noisy compared to POW-r #3 - but again, this is well below the normal hearing threshold at normal playback volume. POW-r #1 isn't flat dither (which is called TPDF) but it sounds fairly close to the pleasant hiss you get from analog gear. Please understand that dithering is a special process that reduces the bit depth while optimizing the sound. Having or adding white noise or hiss to a signal and then truncating won't work.

For very dynamic pieces, such as classical music and some electronica/ambient tracks, I use POW-r#3 (noise shaping). It's one of the more effective bit depth reduction optimization algorithms out there, and very quiet. So there's very little hiss but instead you could detect a very low level high pitched sound. This is only audible during quiet passages and only if you turn up the volume a lot. A whole lot. Unlike TPDF, noise shaping should never be applied several times as the high pitched sound will increase in volume. Same goes for colored dither (#1) but it's less of a problem than noise shaping.

I never use POW-r #2 since I don't like the sound of its shaping compared to the effectiveness and sound of POW-r #3.

I use Waves. They are always asking about dither. Should I use their dither? Is logics dither different? Is using a lot of waves plugs that have dither on/off effecting my sound?

Every time you go from a higher bit depth to a lower bit depth, dithering should be applied. However, applying multiple rounds of shaped dither and especially noise shaping (like some Waves IDR algorithms) should be avoided.

Waves are different from most other plug-ins since they output a 24 bit fixed signal instead of a 32 bit floating point signal (at least last I checked). I would simply go with the 24 bit output and not use the IDR option.

So: don't activate the dither option in your plug-ins if you're using them as part of a chain but make sure the plug-ins are set to output 24 bits or higher (some plug-ins offer you a choice in a preference menu or directly on the interface).

If you plan to get your mix mastered somewhere else or do the mastering yourself in a separate project then I recommend that you bounce to 24 bits WAV without any extra dithering. I believe Logic self-dithers with TPDF from floating point to 24 bit anyway.

Then as you bounce your final master to 16 bits WAV you add POW-r #1 or #3.

Once you've dithered to 16 bits you should not process the file again in any way. Any kind of processing will ruin the point of dithering. You can chop off the start and end points destructively (in the Sample Editor) but that's it, no fades or anything else.

Just to update this 5 year old thread, since I've received a couple of emails on the subject:

I believe Logic self-dithers with TPDF from floating point to 24 bit anyway.

I did some new tests with LPX and my conclusion is that LPX does not apply any automatic dither (such as TPDF) when quantizing from 32 bit float.

I generated a very low level test signal and compared the 32 bit floating point live stream in LPX to a bounced 24 bit truncated version of the same signal using AU NetSend from LPX to Audiofile Spectre. I also compared the spectral analysis in Izotope RX Advanced of dithered and non-dithered bounces, which shows no sign of automatic or hidden dither being applied to 24 bit bounces in LPX. All I see is truncation in both 24 bit and 16 bit bounces when no dither is applied.

We earlier concluded that Logic (originally back in version 8, I think) was applying auto dither. This was based on tests that showed an unexpected (but small) increase in peak level and spectral analysis that showed information which ought to have been truncated.

However, I now believe that we drew a hasty conclusion. The weird level change was real, but it was likely some kind of low order bit error in Logic Pro. I believe we saw the same behavior in Pro Tools at the time.

Thanks from me too!

I've wondered about this many times myself and had not found a way to confirm it.

I did some new tests with LPX and my conclusion is that LPX does not apply any automatic dither (such as TPDF) when quantizing from 32 bit float.

Hi guys, Lagerfeldt I'm so glad you tested this.!

Does this mean one has to apply dither when bouncing to a 24 bit WAV/AIFF/CAF file from 32 bit floating point?

Forgive me if the answer is already written, suggested or in between the lines, I'm relatively new to dithering..

Since Logic doesn't add dither from 32 bit float to 24 bit then you could choose to add dither. However, since all the dither algorithms in Logic are shaped you don't have a choice of simple flat/TPDF dither.

Pitching or reprocessing the bounce file not only destroy the dither but in the case of pitching could in theory make the dither audible, especially if you apply several rounds of dither down the line.

I have no problem bouncing to 24 bit without dither, but in theory it's a good idea to at least apply TPDF when reducing wordlength.

The short answer is: it's extremely unlikely you will notice any difference from 32 bit float > 24 bit with or without dither applied.

it's extremely unlikely you will notice any difference from 32 bit float > 24 bit with or without dither applied.

This is how I'm approaching it.

If you still want to add dither you can use this little free gem:

DitherTo | Airwindows

I have no problem bouncing to 24 bit without dither, but in theory it's a good idea to at least apply TPDF when reducing wordlength.

 

The short answer is: it's extremely unlikely you will notice any difference from 32 bit float > 24 bit with or without dither applied.

Yeah, personally I haven't had any issues so far not dithering from 32 to 24.. Thanks for the plugin tip Eric.

Ultimately, would you guys say it's unnecessary having it as a standard to bounce both dithered and un-dithered versions of my tracks/files if they're gonna be sent off to mastering? Would a 32 to 24 TPDF be in the way of a 24 to a 16 dither?

Thanks for the plugin tip Eric.

You're welcome!

Ultimately, would you guys say it's unnecessary having it as a standard to bounce both dithered and un-dithered versions of my tracks/files if they're gonna be sent off to mastering?

My very personal opinion:

I can see myself using TPDF dither when bouncing the whole project for mastering. I wouldn't bother with 2 versions. Either with or without, not a biggie.

Where it all falls apart is when you want to BiP within the project. It's so counter productive to always insert a dithering plug-in on every track that I need to bounce. The positive aspects are here far, far to small to compensate for the loss in creative workflow.

There are other aspects that require my attention.

Would a 32 to 24 TPDF be in the way of a 24 to a 16 dither?

If you are truncating from 32-bit to 16-bit then, Yes.

If you are truncating to 24 and then decide to go to 16-bit then, No.

My very personal opinion:

I can see myself using TPDF dither when bouncing the whole project for mastering. I wouldn't bother with 2 versions. Either with or without, not a biggie.

 

Where it all falls apart is when you want to BiP within the project. It's so counter productive to always insert a dithering plug-in on every track that I need to bounce. The positive aspects are here far, far to small to compensate for the loss in creative workflow.

There are other aspects that require my attention.

I see.

Would a 32 to 24 TPDF be in the way of a 24 to a 16 dither?

If you are truncating from 32-bit to 16-bit then, Yes.

If you are truncating to 24 and then decide to go to 16-bit then, No.

So a dither from 32-bit to 24-bit is not ruining it for the master engineer's use of dither when he's going from 24-bit to 16-bit after mastering, right?

So a dither from 32-bit to 24-bit is not ruining it for the master engineer's use of dither when he's going from 24-bit to 16-bit after mastering, right?

Correct.

So a dither from 32-bit to 24-bit is not ruining it for the master engineer's use of dither when he's going from 24-bit to 16-bit after mastering, right?

 

Correct.

Thank you Eric.! Have a good one!