Claims
- 1. A method for encoding N input audio signals, N>1, comprising the steps of:
(a) converting each of the N input audio signals into a plurality of spectral components in a frequency domain; (b) for each of one or more, but not all, of the spectral components, downmixing the spectral components corresponding to the N input audio signals to generate a downmixed spectral component, leaving one or more of the spectral components for each of the N input audio signals unmixed; and (c) generating an encoded audio bitstream based on the one or more downmixed spectral components and one or more unmixed spectral components.
- 2. The invention of claim 1, wherein step (c) comprises the steps of:
(1) converting the one or more downmixed spectral components and the one or more unmixed spectral components into N hybrid audio signals in a time domain; and (2) applying an audio coding algorithm to the N hybrid audio signals to generate the encoded audio bitstream.
- 3. The invention of claim 1, wherein step (b) further comprises the step of generating one or more auditory spatial parameters for the one or more downmixed spectral components.
- 4. The invention of claim 3, wherein the one or more auditory spatial parameters include one or more of an inter-channel level difference and an inter-channel time difference.
- 5. The invention of claim 1, wherein:
N=2; the two input audio signals correspond to left and right input audio signals of a stereo input audio signal; each downmixed spectral component is a mono spectral component; and the encoded audio bitstream is generated using a stereo audio coder.
- 6. The invention of claim 1, wherein:
the one or more downmixed spectral components have frequencies above a specified threshold frequency; and the one or more unmixed spectral components have frequencies below the specified threshold frequency.
- 7. The invention of claim 6, wherein the specified threshold frequency varies dynamically over time.
- 8. The invention of claim 7, wherein the specified threshold frequency varies as a function of bit-rate.
- 9. The invention of claim 1, wherein:
the one or more downmixed spectral components have spectral energies below a specified threshold energy; and the one or more unmixed spectral components have spectral energies above the specified threshold energy.
- 10. An encoded audio bitstream generated by:
(a) converting each of N input audio signals, N>1 into a plurality of spectral components in a frequency domain; (b) for each of one or more, but not all, of the spectral components, downmixing the spectral components corresponding to the N input audio signals to generate a downmixed spectral component, leaving one or more of the spectral components for each of the N input audio signals unmixed; and (c) generating the encoded audio bitstream based on the one or more downmixed spectral components and one or more unmixed spectral components.
- 11. The invention of claim 10, wherein step (c) comprises the steps of:
(1) converting the one or more downmixed spectral components and the one or more unmixed spectral components into N hybrid audio signals in a time domain; and (2) applying an audio coding algorithm to the N hybrid audio signals to generate the encoded audio bitstream.
- 12. The invention of claim 10, wherein the encoded audio bitstream comprises one or more auditory spatial parameters for the one or more downmixed spectral components.
- 13. The invention of claim 10, wherein:
N=2; the two input audio signals correspond to left and right input audio signals of a stereo input audio signal; each downmixed spectral component is a mono spectral component; and the encoded audio bitstream is generated using a stereo audio coder.
- 14. An apparatus for processing N input audio signals, N>1 for encoding, comprising:
(a) one or more transforms configured to convert each of the N input audio signals into a plurality of spectral components in a frequency domain; and (b) a downmixer configured, for each of one or more, but not all, of the spectral components, to downmix the spectral components corresponding to the N input audio signals to generate a downmixed spectral component, leaving one or more of the spectral components for each of the N input audio signals unmixed.
- 15. The invention of claim 14, further comprising one or more inverse transforms configured to convert the one or more downmixed spectral components and the one or more unmixed spectral components into N hybrid audio signals.
- 16. The invention of claim 14, further comprising an audio coder configured to generate an encoded audio bitstream based on the one or more downmixed spectral components and the one or more unmixed spectral components.
- 17. The invention of claim 14, further comprising a generator configured to generate one or more auditory spatial parameters for the one or more downmixed spectral components.
- 18. The invention of claim 14, wherein:
N=2; the two input audio signals correspond to left and right input audio signals of a stereo input audio signal; each downmixed spectral component is a mono spectral component; and a stereo audio coder can generate an encoded audio bitstream based on the one or more downmixed spectral components and the one or more unmixed spectral components.
- 19. The invention of claim 14, wherein:
the one or more downmixed spectral components have frequencies above a specified threshold frequency; and the one or more unmixed spectral components have frequencies below the specified threshold frequency.
- 20. A method for decoding an encoded audio bitstream, comprising the steps of:
(a) decoding the encoded audio bitstream to generate a plurality of spectral components in a frequency domain, wherein:
one or more sets of the spectral components correspond to downmixed spectral components; and one or more sets of the spectral components correspond to unmixed spectral components; (b) for each set of the downmixed spectral components, applying one or more auditory spatial parameters to generate a synthesized spectral component; and (c) converting the synthesized spectral components and the unmixed spectral components into N decoded audio signals in a time domain, N>1.
- 21. The invention of claim 20, wherein step (a) comprises the steps of:
(1) decoding the encoded audio bitstream to recover N hybrid audio signals; and (2) converting each of the N hybrid audio signals into the plurality of spectral components in the frequency domain.
- 22. The invention of claim 21, wherein:
N=2; the encoded audio bitstream is decoded using a stereo audio decoder; the two hybrid audio signals correspond to left and right hybrid audio signals of a hybrid stereo audio signal; and each downmixed spectral component is a mono spectral component.
- 23. The invention of claim 20, wherein:
the one or more downmixed spectral components have frequencies above a specified threshold frequency; and the one or more unmixed spectral components have frequencies below the specified threshold frequency.
- 24. An apparatus for decoding an encoded audio bitstream, comprising:
(a) an audio decoder configured to decode the encoded audio bitstream to generate a plurality of spectral components in a frequency domain, wherein:
one or more sets of the spectral components correspond to downmixed spectral components; and one or more sets of the spectral components correspond to unmixed spectral components; (b) a synthesizer configured, for each set of the downmixed spectral components, to apply one or more auditory spatial parameters to generate a synthesized spectral component; and (c) one or more inverse transforms configured to convert the synthesized spectral components and the unmixed spectral components into N decoded audio signals in a time domain, N>1.
- 25. The invention of claim 24, wherein:
the audio decoder is configured to decode the encoded audio bitstream to generate N hybrid audio signals; and further comprising one or more transforms configured to convert each of the N hybrid audio signals into the plurality of spectral components in the frequency domain.
- 26. The invention of claim 25, wherein:
N=2; the encoded audio bitstream is decoded using a stereo audio decoder; the two hybrid audio signals correspond to left and right hybrid audio signals of a hybrid stereo audio signal; and each downmixed spectral component is a mono spectral component.
- 27. The invention of claim 24, wherein:
the one or more downmixed spectral components have frequencies above a specified threshold frequency; and the one or more unmixed spectral components have frequencies below the specified threshold frequency.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of the filing date of U.S. provisional application no. 60/391,095, filed on Jun. 24, 2002 as attorney docket no. Baumgarte 3-11. The subject matter of this application is related to the subject matter of U.S. patent application Ser. No. 09/848,877, filed on 05/04/2001 as attorney docket no. Faller 5 (“the '877 application”), U.S. patent application Ser. No. 10/045,458, filed on Nov. 7, 2001 as attorney docket no. Baumgarte 1-6-8 (“the '458 application”), U.S. patent application Ser. No. 10/155,437, filed on May 24, 2002 as attorney docket no. Baumgarte 2-10 (“the '437 application”), and U.S. patent application Ser. No. xx/xxx,xxx, filed on the same date as the present application as attorney docket no. Baumgarte 4 (“the 'xxx application”), the teachings of all of which are incorporated herein by reference.
Provisional Applications (1)
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Number |
Date |
Country |
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60391095 |
Jun 2002 |
US |