An audio decoder configured to determine a reconstructed frame of an audio signal from an access unit of a received data stream; wherein the access unit comprises waveform data and metadata ; wherein the waveform data and the metadata are associated with the same reconstructed frame of the audio signal ; wherein the audio decoder comprises - a waveform processing path configured to generate a plurality of waveform subband signals from the waveform data ; - a metadata processing path configured to generate decoded metadata from the metadata ; and - a metadata application and synthesis unit configured to generate the reconstructed frame of the audio signal from the plurality of waveform subband signals and from the decoded metadata ; wherein the frame of the audio signal comprises a lowband signal and a highband signal; the plurality of waveform subband signals being indicative of the lowband signal and the metadata being indicative of a spectral envelope of the highband signal; wherein the metadata application and synthesis unit comprises a metadata application unit which is configured to perform high frequency reconstruction using the plurality of waveform subband signals and the decoded metadata ; and wherein the waveform processing path comprises a waveform delay unit which is configured to delay the plurality of waveform subband signals , and the metadata processing path comprises a metadata delay unit configured to delay the decoded metadata , the waveform delay unit and the metadata delay unit being configured to time-align the plurality of waveform subband signals and the decoded metadata , and wherein the waveform processing path comprises an analysis unit configured to generate the plurality of waveform subband signals, and the analysis unit is configured to introduce a fixed delay which is independent of the frame length N of the reconstructed frame of the audio signal . - a waveform processing path configured to generate a plurality of waveform subband signals from the waveform data ; - a metadata processing path configured to generate decoded metadata from the metadata ; and - a metadata application and synthesis unit configured to generate the reconstructed frame of the audio signal from the plurality of waveform subband signals and from the decoded metadata ; wherein the frame of the audio signal comprises a lowband signal and a highband signal; the plurality of waveform subband signals being indicative of the lowband signal and the metadata being indicative of a spectral envelope of the highband signal; wherein the metadata application and synthesis unit comprises a metadata application unit which is configured to perform high frequency reconstruction using the plurality of waveform subband signals and the decoded metadata ; and wherein the waveform processing path comprises a waveform delay unit which is configured to delay the plurality of waveform subband signals , and the metadata processing path comprises a metadata delay unit configured to delay the decoded metadata , the waveform delay unit and the metadata delay unit being configured to time-align the plurality of waveform subband signals and the decoded metadata , and wherein the waveform processing path comprises an analysis unit configured to generate the plurality of waveform subband signals, and the analysis unit is configured to introduce a fixed delay which is independent of the frame length N of the reconstructed frame of the audio signal . <EOS>