I've been stumbling around dither information for a couple of days, mainly as a refresh, but after using Vegas Video's dither on my 64bitmaster file for an animation I'm working on...I've realized and worked some things out about dither.
Firstly for mastering to a 24bit master file...I've discovered that Vegas Video's (which probably was coded by Sony?) is better than any of the other dithers I've got. This includes Sonar's and Wave's L16 Ultramaxamizer. For one I can hear the subtle changes each setting produces. Amazing, when I discovered this. This dither is very different to the ones we're all probably used to here on this forum. It doesn't have powr, but instead just plain triangle, rectangle and half versions of these, as well as gaussian. From the little I've read, however, it seems these are the more 'normal' settings avaliable as dither settings. The noise shaping allows you to shift the dither noise from the hi frequencies or even distribution. Finally, the plug can dither down to 32bitfp.
Now I've been rabbiting on about 64bitfp audio files and in particular for master files. One of the more interesting things I've been investigating is using an undithered 64bitfp audio file for MP3s, and from what I've been reading - I'm right...although most of the knowledge base is quite old and mostly talking about 32bitfp audio files. I say this because I bounced out a 64bit undithered master and uploaded to soundcloud...yes soundcloud does accept 64bitfp master files, and I also MP3 that same file using Pyro, and finally I also had a 24bit master, except I used Wave's L16 ultramaximizer instead of the Adaptive Limiter (I prefer the Adaptive), but I was puzzled as to why the MP3 and Soundcloud sounded better than the 24bit master, and to my ears soundcloud sounded better than the MP3, but now I know what I was hearing...the soundcloud and MP3 conversion add in a similar noise to dither - it's one reason why so many MP3s and soundcloud files sound so **** - double dither if you like. But now I can hear what's being added in via Vegas Video's dither - I know that a simple dither, and one that is more controllable is far better than either of the aforementioned dithers I've used in the past. And I could blame these dithers for my misunderstanding of practical uses for dither.
So to recap...use dither if you're processing at 64bit fp and plan to create a 24bit master and God forbid a 16 bit master. I don't create 16bit masters - they're virtually obsolete! I would use your ears if you're creating a 24bit master and are only processing at 32bitfp...there's conjecture about best practices in regards to dither and converting 32bit into 24bit, but dither if you're going from 32bit to 16bit. As for MP3s and soundcloud - don't dither and export the highest possible bit depth you recorded and processed at. My advice is leave that 64bit button on for both audio and processing - with this caveat - if you're primarily recording acoustic instruments and will do minimal processing in the ethereal realm - then 32bit and even 24bit will be fine. It just depends on outboard equipment and the asethetic you're after. As for the other compressed formats - I'm still working on best practice. The master file should always be 64bit, but I'm unsure about dither. I'm working on my 3d animation and I have a 64bit master audio file, and I placed the Vegas Dither over the top with a 32bit quantize setting and it cleaned up the very tip of the resolution - clearing away a bit of the harshness to my ears and focusing the bottom end...but whether I need to keep this dither on when I convert to an MP4 I'm not sure yet and wont know until I bounce out one with and one without. ITunes AC3 format - I'm not sure either, but theoretically it should be the same as an MP3. I'm going to look around for just a noise shaper plug without the quantize - because an MP3 created from a 64vit master file without dither could use a little noise shaping?
I'm sort of on-topic I hope :).
Ben