A method of identifying a traced media playback decoder embedded in a device, wherein data representative of a trace message is included in the content field of a media content file and a trigger string (16) is included in the user data field of the file. The file is input to the decoder, and a traced decoder is arranged and configured to render the trace message in a desired format in response to detection of the trigger string. If the decoder is not the traced decoder, the trigger string will be disregarded and the component will try and process the media content file like a normal media content file, which results in an error.