A decoder for decoding an encoded MPEG-D USAC bitstream, the decoder comprising: a receiver configured to receive the encoded bitstream, wherein the bitstream represents a sequence of audio sample values and comprises a plurality of frames, wherein each frame comprises associated encoded audio sample values, wherein the bitstream comprises a pre-roll element including one or more pre-roll frames needed by the decoder to build up a full signal so as to be in a position to output valid audio sample values associated with a current frame, and wherein the bitstream further comprises a USAC configuration element comprising a current USAC configuration as payload and a current bitstream identification; a parser configured to parse the USAC configuration element up to the current bitstream identification and to store a start position of the USAC configuration element and a start position of the current bitstream identification in the bitstream; a determiner configured to determine whether the current USAC configuration differs from a previous USAC configuration by checking a length of the current USAC configuration config_length_in_bits against the length of the previous USAC configuration, and, if the current USAC configuration differs from the previous USAC configuration, store the current USAC configuration, wherein the determiner is configured to jump back to the start position of the USAC configuration element in the bitstream and to bulk read and store the unparsed USAC configuration payload of (config_length_in_bits + 7)/8) bytes; and an initializer configured to initialize the decoder if the determiner determines that the current USAC configuration differs from the previous USAC configuration, wherein initializing the decoder comprises: decoding the one or more pre-roll frames included in the pre-roll element, switching the decoder from the previous USAC configuration to the current USAC configuration, thereby configuring the decoder to use the current USAC configuration if the determiner determines that the current USAC configuration differs from the previous USAC configuration, and wherein the decoder is configured to discard and not decode the pre-roll element if the determiner determines that the current USAC configuration is identical with the previous USAC configuration. a receiver configured to receive the encoded bitstream, wherein the bitstream represents a sequence of audio sample values and comprises a plurality of frames, wherein each frame comprises associated encoded audio sample values, wherein the bitstream comprises a pre-roll element including one or more pre-roll frames needed by the decoder to build up a full signal so as to be in a position to output valid audio sample values associated with a current frame, and wherein the bitstream further comprises a USAC configuration element comprising a current USAC configuration as payload and a current bitstream identification; a parser configured to parse the USAC configuration element up to the current bitstream identification and to store a start position of the USAC configuration element and a start position of the current bitstream identification in the bitstream; a determiner configured to determine whether the current USAC configuration differs from a previous USAC configuration by checking a length of the current USAC configuration config_length_in_bits against the length of the previous USAC configuration, and, if the current USAC configuration differs from the previous USAC configuration, store the current USAC configuration, wherein the determiner is configured to jump back to the start position of the USAC configuration element in the bitstream and to bulk read and store the unparsed USAC configuration payload of (config_length_in_bits + 7)/8) bytes; and an initializer configured to initialize the decoder if the determiner determines that the current USAC configuration differs from the previous USAC configuration, wherein initializing the decoder comprises: decoding the one or more pre-roll frames included in the pre-roll element, switching the decoder from the previous USAC configuration to the current USAC configuration, thereby configuring the decoder to use the current USAC configuration if the determiner determines that the current USAC configuration differs from the previous USAC configuration, and wherein the decoder is configured to discard and not decode the pre-roll element if the determiner determines that the current USAC configuration is identical with the previous USAC configuration. decoding the one or more pre-roll frames included in the pre-roll element, switching the decoder from the previous USAC configuration to the current USAC configuration, thereby configuring the decoder to use the current USAC configuration if the determiner determines that the current USAC configuration differs from the previous USAC configuration, and wherein the decoder is configured to discard and not decode the pre-roll element if the determiner determines that the current USAC configuration is identical with the previous USAC configuration.