Buffering packets of a media stream for transmission from a transmitting device to a receiving device. Media packets are formed from at least one kind of media information in a stream generator; at least one transmission frame is generated on the basis of media packets to be transmitted; packets to be transmitted are formed from the at least one transmission frame ; and a transmission schedule is generated for packets to be transmitted. In addition, a first step and a second step of hypothetical decoding are also performed. The first step of hypothetical decoding is performed according to the transmission schedule and comprises buffering the packets to be transmitted according to the transmission schedule to a first hypothetical decoding buffer; and outputting packets from the first hypothetical decoding buffer on a transmission frame basis. The second step of hypothetical decoding comprises controlling the buffer occupancy level of the first hypothetical decoding buffer and the second hypothetical decoding buffer by controlling at least one of the following: the operation of the stream generator; the generation of at least one transmission frame; the transmission schedule.