The invention relates to a device (10) for producing an encoded data stream which represents an audio and/or video signal. Said device comprises an encoder (16) for encoding an input signal (12) to produce a data stream of a defined data stream syntax as the output signal. Said device further comprises an encryption device (18) which is coupled to the encoder (16) to influence encoding-related data (20a) and/or the output signal (20b) of the encoder in an unequivocally reversible manner on the basis of a code in such a manner that the produced encoded data stream contains useful information that differs from the useful information of a data stream that would be produced by the device without the presence of the encryption device and that the produced encoded data stream has the defined data stream syntax. The invention thus provides a flexible data stream encryption according to which the degree of encryption can be freely selected in such a manner that the user of a decoder who does not possess the code still has a rough idea of the audio and/or video signal that might cause him/her to buy the code to hear or view the audio and/or video signal in its full quality. The encoder-specific encryption and decryption concept can be implemented into already existing encoders/decoders with little effort.