What is the "VST Bridge"?
The VST Bridge is a kind of mediator between components which can not "speak" to each other due to technical circumstances. This can be the case in following constellations:
A: You have an Intel-based Apple Macintosh computer with Cubase/Nuendo 4 (or higher) running as host application and executed as Intel binary. You want to use VST plug-ins which are only available as PowerPC binary.
B: You have a 64-bit PC Windows system using Windows Vista 64-bit. You want to run the 64-Bit Preview version of Cubase/Nuendo with plug-ins only available as 32-Bit version.
In both cases the VST Bridge is needed as a mediator to execute program code not natively available for the used platform. In case A PowerPC code is translated to Intel code, in case B the 32-bit code is translated in a way to execute it within a pure 64-bit environment.
You can imagine the VST Bridge as a kind of simultaneous translator for program code. There are no additional latencies introduced but the computer needs resources for the translation. A plug-in which runs through the VST Bridge can not be executed as efficiently a version available in native program code. Consequently, the usage of "bridged" plug-ins can result in higher CPU load and the plug-in user interface may react slowly.
Following the VST (2.4) specifications is very important for bridged plug-ins. However, even if a plug-in used through the VST Bridge crashes and potentially crashes the VST Bridge itself, the host application remains unaffected. The VST Bridge runs as a separate process in the system and is not part of the host application process.
The VST Bridge is meant as a transitional aid. It offers the possibility to switch from a PowerPC-based Apple Macintosh computer to an Intel-based model, respectively to switch from a 32-bit PC Windows system to a pure 64-bit environment. Your Cubase/Nuendo projects can be opened without missing plug-ins (if installed) on your new system to the greatest possible extent.
Please keep in mind that all 32-bit plug-ins used via the VST Bridge still have to share a maximum of 4 GB RAM - the 32-bit limit remains regardless of the overall installed and available system memory.
Nevertheless, plug-ins used through the VST Bridge should be replaced as soon as possible. As an alternative you could create audio exports of affected tracks. To make you aware of which plug-ins need the VST Bridge they will be marked with a symbol in front of their names:
Either there is a plug-in update for your platform available from the respective manufacturer or you try the opportunity to replace bridged plug-ins by the native VST 3 plug-ins included with Cubase and Nuendo, where applicable. The new VST 3 plug-ins can be identified by a three cursive lines symbol in front of the plug-in name. These highclass plug-ins are running natively on all supported plattforms and offer all features needed for nearly every use case of sound design and mixing in the daily studio routine.