The Repository and the Transform Service T-Router uses the T-Engine configuration in combination with their own pipeline files to choose which T-Engine will perform a transform. A transformer definition contains a supported list of source and target Media Types. This is used for the most basic selection. This is further refined by checking that the definition also supports transform options (parameters) that have been supplied in a transform request, or a Rendition Definition used in a rendition request. See Configure a Custom Rendition.
Transformer 1 defines options: Op1, Op2
Transformer 2 defines options: Op1, Op2, Op3, Op4
Rendition provides values for options: Op2, Op3
If we assume that both transformers support the required source and target Media Types, Transformer 2 will be selected because it knows about all the supplied options. The definition may also specify that some options are required or grouped.
The configuration may impose a source file size limit resulting in the selection of a different transformer. Size limits are normally added to avoid the transforms consuming too many resources. The configuration may also specify a priority which will be used in Transformer selection if there are a number of options. The highest priority is the one with the lowest number.