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Offline chrisNova777

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RTAS vs AudioSuite
« on: August 22, 2014, 12:26:23 AM »

Audiosuite what, RTAS who? The ProTools plug-in mystery solved

When it comes to plug-ins in ProTools when using LE or M-Powered there are really only two viable options open to you, Audiosuite or RTAS plug-ins. Do you know the difference? Do you even use Audiosuite plugs? What is RTAS? Why should I care about Audiosuite? Well hopefully after reading this you will understand a little more about the differences, and when to use these powerful plug-ins and when not to.

There are actually three different types of plug-in available for ProTools software, these are Audiosuite, RTAS, and TDM. The TDM plug-ins use ProTools HD / TDM hardware which the university doesn’t have so these will not be covered in great detail. The main focus for us are the Audiosuite and RTAS plug-ins as the university has over £1000 worth of plug-ins for students to use, it’s probably best to know the differences. These Audiosuite and RTAS plug-ins are known as Native plug-ins as they use the local “native” CPU for their processing.

The first type of plug-in I’ll go into are the RTAS type of plug-in, which actually stands for Real Time AudioSuite plug-in. Now as you can probably deduct from the name these plug-ins work in real time, meaning that as soon as you change a parameter inside a plug-in the sound is changed in real time depending on what you are doing, for example if you are using a 4-bamd EQ and you increase the gain for the low-end you will hear the changes being made as you adjust the gain.

This can be great for EQ as you can sweep through the frequencies to find ones that make the sound “pop”, or sweep through to remove that annoying “fizzing” sound. Whatever the parameter of an RTAS plug-in when it is altered the changes are instant. There is obviously a trade off with this which is you loose a lot of processing power from the host CPU when using RTAS plug-ins, certain plugs will use more than others but they all use a lot. The worst plug-in I’ve used for using host CPU power was Izotope’s Ozone mastering plug-in, an extremely powerful plug, but also a very power hungry one.

This is a problem that TDM plug-ins don’t have as they use the dedicated DSP power to use in the host HD / TDM cards, depending on the amount of host cards you are running in a TDM compatible system you could run 3-4 times as many plug-ins than a Native system. In addition to these TDM plug-ins you can also run RTAS plug-ins making use of the local CPU also making a very powerful system.

Now RTAS plug-ins are Real Time AudioSuite plug-ins, Audiosuite plug-ins are versions of these RTAS plug-ins, but they are not real time processing. If we look back at the example of using a 4-band EQ to sweep through frequencies to find that sweet spot to either pull or push the gain in RTAS plugs, that functionality is lost in an Audiosuite plug-in. The processing is done once the user sets all the parameters and then clicks process, this will create a new version of the affected regions and replace the old un-processed ones with the newly processed ones. This is great for a reverse effect as a plug-in would potentially need a very large look ahead buffer to do that effect in real-time which means higher CPU usage, however if this is already processed the CPU wouldn’t need to do anything after the effect has been added.

Audiosuite plug-ins are great once you have found the perfect sound as you can use the RTAS plug-in to find the settings you wish to use, then you can copy those to an Audiosuite plug-in and process the regions that need processing, once this is done you can remove the RTAS plug-in and therefore remove the need for the CPU use valuable processing power on an EQ for example. I am using EQ as an example however that doesn’t mean this is limited to EQ, you can run compressors RTAS find the right settings, then process the audio using the Audiosuite plug-in and remove the RTAS recovering those CPU cycles. Virtually any RTAS plug-in can be used as an Audiosuite plug-in as long as the makers of the plug-in built the functionality into it, there are a few that don’t have this option and it’s for that reason saving as much CPU power as possible is advised.

That’s pretty much all for this one, so to conclude and summarize -

RTAS is real-time meaning that even if the plug-in is just sitting on a channel it is using up CPU cycles, the more complex the plug-in the higher the CPU usage with that plug-in. Audiosuite plug-ins are not real-time meaning that they don’t use CPU power once they have processed the audio so that CPU power can be used elsewhere. I would recommend doing the following when using any processing on your tracks -

    Use RTAS plug-ins to pre-process and find those “perfect” settings for a sound
    Copy the settings to an Audiosuite equivalent plug-in and process the audio using that if possible
    Remove the RTAS plug-in and recover the CPU power that was being used by it to use again
    Use RTAS plug-ins sparingly as they can add some degree of delay if heavy on the CPU