VST vs AU

[Tallisman]

I was wondering if AU offers any advantage over VST? I am certain that the maths will be the same, but does either standard have the upper hand in terms of CPU hit?

I am asking as I have just noticed a ton of wicked Shcwa and stillwell plugins offered now in both flavours. :eek: :D

thanks and many greetings

.t

[schwa]

One significant difference is that all AUs are 32-bit IO only.

As far as CPU there might be a slight extra cost to AU but it's likely insignificant in the grand scheme of things.

[Tallisman]

whereas the ReaPlugs and VST versions of SCHWA and Stillwell plugs are 64bit i/o?


.t

[schwa]

It's a built in limitation of AU that the data to and from the plugin is 32 bits. So a in a 64 bit host, a plugin (like reaplugs or Stillwell/Schwa) that does 64 bit internal processing will get the samples chopped off on the way in and the way out.

FWIW in normal use this truncation wouldn't make a discernible difference to the sound.

Also FWIW, this probably means all *other* AU hosts are 32-bit signal chain throughout.

[GravyTrain]

In other words, AUs are generally better but with a slight extra CPU usage?

[Sonic Vampire]

In other words, AUs are generally better but with a slight extra CPU usage?

no, they are only 32bit i/o (input/output), not 64bit like reaplugs
more bits = better

FYI, except for above mentioned plugs, all the ones I have tested are 32bit i/o anyway

get schwa's "bitter", a free plugin that will show you this

[Tallisman]

In other words, AUs are generally better but with a slight extra CPU usage?

They are only better if the VST version is not available...

lets see if I can make some text art


-------------------------------------- -----
host's ---------_____________________
64 bit---------------
pipeline---------AU's 32bit processing
---------------_____________________
-------------------------------------- -----

so using the AU version will add (probably negligible )CPU overhead due the process of chopping 64bit to 32bits to get it into the AU plugin. I have no idea if the AU plugins are capable of processing the audio at 64 bits or greater... If the are, and do, at the end of that processing the AU will chop it down again to 32bits, ship it through it's 32bit output back to the host which, in this case is 64bits.

I'll be using the VST versions wherever possible, 'cause all this chopping makes me nervous. I know that I cannot hear the difference between 32bits and 64bits... but I don't care.

My question is: Are these plugins dithering? and if so how good are these dithering algorithms? Has anyone put Span after the vst and au version of the same plugs and compared the output?

:D

greetings
.t

[schwa]

Are these plugins dithering?

No plugin or host would dither when converting a 64 bit float audio stream to 32 bit float ... if you want we can go into the technical details or you can just trust me, it's not something that happens and not something you would want to happen.

In terms of IO bandwidth, AU is just like VST 2.3 and earlier. Any individual AU or VST<=2.3 can choose to use any resolution internally, but the samples being sent from the host and back to the host after the plugin has done its processing will always be 32 bits. VST 2.4 plugins can choose to send 64 bit IO, but not all plugins choose to, and not all hosts support it anyway (Reaper does, of course).

In Reaper, at present, the CPU cost of converting the sample resolution down to 32 bits in order to pass it to an AU or VST<=2.3 is negligible.

[Tallisman]

Oh I have nothing but trus for you schwa (my recent tree-hugging should suffice as evidence :D).

I am happy to hear there is no dithering going on there, and also happy to know that dithering in such places is not needed.

I am also happy to not have to rely on AU for my favourite plugins, though I am happy reaper supports them and I am warming up to the idea of AUs :D.

Speaking of which, any plans of porting Dyno and sculpto to MacOS? VST or AU?


greetings
.t

[sstillwell]

I may be speaking out of turn, but I believe that all of our collective plugins will be ported eventually to all three platforms; PC VST, Mac OS X VST, and Mac OS X AU. It's just a matter of time and the availability thereof.

Scott

[Tallisman]

cool!
thanks

.t