Circular frequency translation with noise blending

• US 8,285,543 B2
• Filed: 01/24/2012
• Issued: 10/09/2012
• Est. Priority Date: 03/28/2002
• Status: Expired due to Term

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Truman, Michael Mead, Vinton, Mark Stuart
• Primary Examiner(s): YEN, ERIC L
• Application Number:
  US13/357,545
• Publication Number:
  US 20120128177A1
• Time in Patent Office: 259 Days
• Field of Search: 704/200, 704/200.1, 704/201, 704/205, 704/226, 704/228
• US Class Current: 704/228
• CPC Class Codes: G10L 19/0017 Lossless audio signal coding; Perfect reconstruction of coded audio signal by transmission of coding error G10L19/24 takes precedence
• CPC Class Codes: G10L 19/002 Dynamic bit allocation for perceptual audio coders G10L19/032
• CPC Class Codes: G10L 19/012 Comfort noise or silence coding
• CPC Class Codes: G10L 19/02 using spectral analysis, e.g. transform vocoders or subband vocoders
• CPC Class Codes: G10L 19/0204 using subband decomposition
• CPC Class Codes: G10L 19/0208 Subband vocoders
• CPC Class Codes: G10L 19/0212 using orthogonal transformation
• CPC Class Codes: G10L 19/028 Noise substitution, i.e. substituting non-tonal spectral components by noisy source comfort noise for discontinuous speech transmission G10L19/012
• CPC Class Codes: G10L 19/03 Spectral prediction for preventing pre-echo; Temporary noise shaping [TNS], e.g. in MPEG2 or MPEG4
• CPC Class Codes: G10L 19/06 Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
• CPC Class Codes: G10L 19/16 Vocoder architecture
• CPC Class Codes: G10L 19/167 Audio streaming, i.e. formatting and decoding of an encoded audio signal representation into a data stream for transmission or storage purposes
• CPC Class Codes: G10L 19/173 Transcoding, i.e. converting between two coded representations avoiding cascaded coding-decoding
• CPC Class Codes: G10L 19/26 Pre-filtering or post-filtering
• CPC Class Codes: G10L 19/265 Pre-filtering, e.g. high frequency emphasis prior to encoding
• CPC Class Codes: G10L 21/00 Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility G10L19/00 takes precedence
• CPC Class Codes: G10L 21/038 using band spreading techniques
• CPC Class Codes: G10L 21/0388 Details of processing therefor

Abstract

An audio signal is conveyed more efficiently by transmitting or recording a baseband of the signal with an estimated spectral envelope and a noise-blending parameter derived from a measure of the signal'"'"'s noise-like quality. The signal is reconstructed by translating spectral components of the baseband signal to frequencies outside the baseband, adjusting phase of the regenerated components to maintain phase coherency, adjusting spectral shape according to the estimated spectral envelope, and adding noise according to the noise-blending parameter. Preferably, the transmitted or recorded signal also includes an estimated temporal envelope that is used to adjust the temporal shape of the reconstructed signal.

Claims

1. A method performed by a device for generating a reconstructed signal that comprises:

the device receiving a signal containing data representing a baseband signal derived from an audio signal, a noise blending parameter and an estimated spectral envelope;

the device obtaining from the data a frequency-domain representation of the baseband signal, the frequency-domain representation comprising baseband spectral components;

the device generating a noise signal comprising noise-signal spectral components that are weighted in amplitude by a noise blending function that is a function of frequency and the noise blending parameter and that gives greater weight to spectral components at higher frequencies;

the device generating a regenerated signal comprising regenerated-signal spectral components copied from the baseband spectral components in a circular manner into an interval of frequencies and weighted in amplitude by an inverse of the noise blending function;

the device generating noisy regenerated spectral components from a combination of the noise-signal spectral components and the regenerated-signal spectral components, wherein amplitudes of the noisy regenerated spectral components are weighted according to the estimated spectral envelope; and

the device generating the reconstructed signal from a time-domain representation of the baseband spectral components combined with the noisy regenerated spectral components.

2. The method of claim 1, wherein the time-domain representation of the baseband spectral components is obtained to represent segments of the reconstructed signal that vary in length.

3. The method of claim 1 that comprises the device applying a time-domain aliasing cancellation synthesis transform to obtain the time-domain representation of the baseband spectral components.

4. The method of claim 1 that comprises the device adapting the generating of the regenerated signal by changing which baseband spectral components are copied or by changing the frequency amount by which baseband spectral components are copied.

5. The method of claim 1, wherein:

the data also represents one or more additional noise blending parameters; and

the noise blending function is also a function of the one or more additional noise blending parameters.

6. The method of claim 1, wherein the regenerated signal comprises regenerated-signal spectral components copied from the baseband spectral components in a circular manner into one or more additional intervals of frequencies.

7. An apparatus for generating a reconstructed signal that comprises:

means for receiving a signal containing data representing a baseband signal derived from an audio signal, a noise blending parameter and an estimated spectral envelope;

means for obtaining from the data a frequency-domain representation of the baseband signal, the frequency-domain representation comprising baseband spectral components;

means for generating a noise signal comprising noise-signal spectral components that are weighted in amplitude by a noise blending function that is a function of frequency and the noise blending parameter and that gives greater weight to spectral components at higher frequencies;

means for generating a regenerated signal comprising regenerated-signal spectral components copied from the baseband spectral components in a circular manner into an interval of frequencies and weighted in amplitude by an inverse of the noise blending function;

means for generating noisy regenerated spectral components from a combination of the noise-signal spectral components and the regenerated-signal spectral components, wherein amplitudes of the noisy regenerated spectral components are weighted according to the estimated spectral envelope; and

means for generating the reconstructed signal from a time-domain representation of the baseband spectral components combined with the noisy regenerated spectral components.

8. The apparatus of claim 7, wherein the time-domain representation of the baseband spectral components is obtained to represent segments of the reconstructed signal that vary in length.

9. The apparatus of claim 7 that comprises means for applying a time-domain aliasing cancellation synthesis transform to obtain the time-domain representation of the baseband spectral components.

10. The apparatus of claim 7 that comprises means for adapting the generating of the regenerated signal by changing which baseband spectral components are copied or by changing the frequency amount by which baseband spectral components are copied.

11. The apparatus of claim 7, wherein:

the data also represents one or more additional noise blending parameters; and

the noise blending function is also a function of the one or more additional noise blending parameters.

12. The apparatus of claim 7, wherein the regenerated signal comprises regenerated-signal spectral components copied from the baseband spectral components in a circular manner into one or more additional intervals of frequencies.

13. A non-transitory medium that is readable by a device and that records a program of instructions executable by the device to perform a method for generating a reconstructed signal, wherein the method comprises:

receiving a signal containing data representing a baseband signal derived from an audio signal, a noise blending parameter and an estimated spectral envelope;

obtaining from the data a frequency-domain representation of the baseband signal, the frequency-domain representation comprising baseband spectral components;

generating a noise signal comprising noise-signal spectral components that are weighted in amplitude by a noise blending function that is a function of frequency and the noise blending parameter and that gives greater weight to spectral components at higher frequencies;

generating a regenerated signal comprising regenerated-signal spectral components copied from the baseband spectral components in a circular manner into an interval of frequencies and weighted in amplitude by an inverse of the noise blending function;

generating noisy regenerated spectral components from a combination of the noise-signal spectral components and the regenerated-signal spectral components, wherein amplitudes of the noisy regenerated spectral components are weighted according to the estimated spectral envelope; and

generating the reconstructed signal from a time-domain representation of the baseband spectral components combined with the noisy regenerated spectral components.

14. The medium of claim 13, wherein the time-domain representation of the baseband spectral components is obtained to represent segments of the reconstructed signal that vary in length.

15. The medium of claim 13, wherein the method comprises applying a time-domain aliasing cancellation synthesis transform to obtain the time-domain representation of the baseband spectral components.

16. The medium of claim 13, wherein the method comprises adapting the generating of the regenerated signal by changing which baseband spectral components are copied or by changing the frequency amount by which baseband spectral components are copied.

17. The medium of claim 13, wherein:

the data also represents one or more additional noise blending parameters; and

the noise blending function is also a function of the one or more additional noise blending parameters.

18. The medium of claim 13, wherein the regenerated signal comprises regenerated-signal spectral components copied from the baseband spectral components in a circular manner into one or more additional intervals of frequencies.