A media encoder for encoding a stream of media data blocks has an encoder pipeline including a sequence of processing modules for processing a stream of media data blocks, and a pipeline configurator configured effect a switch in the encoder pipeline from one or more first encode parameters to one or more second encode parameters. The first processing module of the pipeline can be configured to associate a trigger value with at least a first media data block processed at the first processing module in accordance with second encode parameters, the trigger value passing to subsequent modules so as to cause those modules to adopt the second encode parameters.