RTAS or Real-Time AudioSuite is a plug-in format developed by Digidesign, now known as Avid Technology. The company is known for its flagship Pro Tools recording and production systems.
RTAS was intended for use with Pro Tools LE, which was bundled with the company’s own Digi 002 audio interface, and Pro Tools M-Powered, which works in conjunction with M-Audio interfaces. RTAS plug-ins can also be used in Pro Tools HD and Pro Tools TDM systems.
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Range of plug-in types
RTAS plug-ins comprise a pretty wide and diverse range. As with VST and AU plug-ins, there are virtual instruments, signal processors of various types, and even utilities for metering, tuning, and the like. There are also free RTAS plug-ins available, although the list is nowhere nearly as extensive as the list of free VST plug-ins.
Pro Tools HD systems are known for their use of hardware DSP cards, from which plug-ins draw their processing power. RTAS plug-ins do not require such cards, drawing their power from the host computer.
The name “Real-Time AudioSuite” offers a hint as to the architecture of the plug-in. These are intended to be run in real time, essentially serving as software replications of the hardware effect processors that are typically patched onto mixer inserts. This distinction contrasts RTAS plug-ins with the offline effects processing of Pro Tools’ AudioSuite plug-ins.
Differences with AudioSuite plug-ins
In addition to effecting audio in real time, RTAS plug-ins differ from AudioSuite plug-ins in other ways. Instead of effecting individual audio segments as AudioSuite plug-ins do, RTAS plug-ins work on entire tracks. It is also possible to utilize up to five individual RTAS instances on a track, as opposed to AudioSuite plug-ins that can only be applied one at a time.
In terms of routing, one of the most important things to remember about RTAS plug-ins is that they process signals from left to right. In a five plug-in chain for example, audio is processed from Insert A to Insert E. Even so, it is possible to achieve different results–some subtle, some drastic–simply by switching the order of the effects around.
Differentiating RTAS from other plug-ins
Pro Tools users that have a few different types of plug-ins may find it difficult to differentiate RTAS plug-ins from all the other entries in their plug-ins list. It is helpful to remember that native plugins will be labeled “Native” in their respective windows in Pro Tools 10. This goes for 32-bit AAX plug-ins as well as RTAS plug-ins.
You could identify the RTAS plug-ins by the size of the “close” button on the plug-in window’s title bar. RTAS plugins have a comparatively smaller blank title bar with a single button for closing the window. In contrast, AXX plug-ins have larger blank title bars with correspondingly large “close” button, in addition to a dummy button just to the right.
Using RTAS in other DAWs
Users of DAWs other than Pro Tools frequently ask if it is possible to use RTAS plug-ins in their own systems. Unfortunately, this is not possible, and it is unlikely that it will ever be possible. Users of programs such as Logic, Cubase, and Sonar will therefore have to content themselves with plug-ins supported by their DAWs.
Furthermore, not all RTAS plug-ins are guaranteed to work in Pro Tools Free, despite the fact that it is an Avid product.
FXpansion, the company that has developed VST-to-AU wrappers among others, has categorically stated that the development of an RTAS-to-VST wrapper is a distinct impossibility. According to the company, this is due to technical as well legal reasons.
Although there are free RTAS plug-ins available, their source code and documentation are not available to the public. Developers that wish to create their own RTAS plug-ins will have to obtain the SDK directly from Avid.
In addition, developers are subject to disclosure restrictions with regard to releasing development-related information on Avid’s products. This essentially rules out open source software for RTAS plug-in development.
It is also worth noting that most RTAS plug-ins utilize some type of copy protection. In most cases, this is the iLok dongle by PACE.
The demise of RTAS
The release of Pro Tools 11 in 2013 spelled the end for RTAS and all other Avid plug-in formats. From that version onward, AAX is the only plug-in format that Pro Tools officially supports. Pro Tools 10.3.8 is the last version that supports the RTAS plug-in format.
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