Audio decoder for interleaving signals
A method for decoding an encoded audio bitstream in an audio processing system is disclosed. The method includes extracting from the encoded audio bitstream a first waveform-coded signal including spectral coefficients corresponding to frequencies up to a first cross-over frequency and performing parametric decoding at a second cross-over frequency to generate a reconstructed signal. The second cross-over frequency is above the first cross-over frequency and the parametric decoding uses reconstruction parameters derived from the encoded audio bitstream to generate the reconstructed signal. The method further includes extracting from the encoded audio bitstream a second waveform-coded signal including spectral coefficients corresponding to a subset of frequencies above the first cross-over frequency and interleaving the second waveform-coded signal with the reconstructed signal to produce an interleaved signal. The interleaved signal is then combined with the first waveform-coded signal.
1. A method for decoding a time frame of an encoded audio bitstream in an audio processing system, the method comprising:
extracting from the encoded audio bitstream a first waveform-coded signal comprising spectral coefficients corresponding to frequencies up to a first cross-over frequency for a time frame;
performing parametric decoding at a second cross-over frequency for the time frame to generate a reconstructed signal, wherein the second cross-over frequency is above the first cross-over frequency and the parametric decoding uses reconstruction parameters derived from the encoded audio bitstream to generate the reconstructed signal;
extracting from the encoded audio bitstream a second waveform-coded signal comprising spectral coefficients corresponding to a subset of frequencies above the first cross-over frequency for the time frame;
interleaving the second waveform-coded signal with the reconstructed signal to produce an interleaved signal for the time frame, and
combining the interleaved signal with the first waveform-coded signal.
2. The method of claim 1 wherein the first cross-over frequency depends on a bit transmission rate of the audio processing system.
3. The method of claim 1 wherein the interleaving comprises (i) adding the second waveform-coded signal with the reconstructed signal, (ii) combining the second waveform-coded signal with the reconstructed signal, or (iii) replacing the reconstructed signal with the second waveform-coded signal.
4. The method of claim 1 wherein either (i) the combining the interleaved signal with the first waveform-coded signal is performed in a frequency domain, or (ii) the performing parametric decoding at the second cross-over frequency to generate the reconstructed signal is performed in a frequency domain.
5. The method of claim 1 wherein the performing parametric decoding comprises either (i) parametric upmixing using upmix parameters or (ii) high frequency reconstruction using high frequency reconstruction parameters.
6. The method of claim 1 wherein the performing parametric decoding comprises performing spectral band replication, SBR.
7. The method of claim 1 further comprising receiving a control signal used during the interleaving to produce the interleaved signal.
8. The method of claim 7 wherein the control signal indicates how to interleave the second waveform-coded signal with the reconstructed signal by specifying either a frequency range or a time range for the interleaving.
9. The method of claim 7 wherein a first value of the control signal indicates that interleaving is performed for a respective frequency region.
10. The method of claim 1 wherein the interleaving is performed before the combining.
11. The method of claim 1 wherein the audio processing system is a hybrid decoder that performs waveform-decoding and parametric decoding.
12. The method of claim 1 wherein the first waveform-coded signal and second waveform-coded signal share a common bit reservoir using a psychoacoustic model.
13. The method of claim 1 wherein the interleaving and the combining are combined into a single stage or operation.
14. The method of claim 1 wherein the first waveform-coded signal and the second waveform-coded signal are signals representing a waveform of an audio signal in the frequency domain.
15. An audio decoder for decoding a time frame of an encoded audio bitstream, the audio decoder comprising:
a demultiplexer for extracting from the encoded audio bitstream a first waveform-coded signal comprising spectral coefficients corresponding to frequencies up to a first cross-over frequency for a time frame;
a parametric decoder operating at a second cross-over frequency to generate a reconstructed signal for the time frame, wherein the second cross-over frequency is above the first cross-over frequency and the parametric decoding uses reconstruction parameters derived from the encoded audio bitstream to generate the reconstructed signal;
a demultiplexer for extracting from the encoded audio bitstream a second waveform-coded signal comprising spectral coefficients corresponding to a subset of frequencies above the first cross-over frequency for the time frame;
an interleaver for interleaving the second waveform-coded signal with the reconstructed signal to produce an interleaved signal for the time frame, and
a synthesizer for combining the interleaved signal with the first waveform-coded signal.
16. A non-transitory computer readable medium comprising instructions that
when executed by a processor perform the method of claim 1 .