Metapass Plug-ins
A metapass plug-in analyzes all files in the batch, collects the results, and processes the files by varying amounts. The result of the analysis of one file can affect how other files are processed.
A typical example of a metapass plug-in is the Loudness Meta Normalizer, which can process a number of files so that they all get the loudness of the loudest file in the batch.
Metapass plug-ins can be freely combined with other types of processors. For example, you can use both the Loudness Meta Normalizer and a regular Normalizer in the same batch. You may also combine metapass plug-ins with multipass plug-ins.
A metapass plug-in requires two processing passes. During the first pass, all the files in the batch are analyzed and during the second pass they are all processed.
This is different from other multipass plug-ins, where each file is analyzed/processed twice or more times if required.