Broadband Frequency Translation for High Frequency Regeneration

• US 20090192806A1
• Filed: 02/24/2009
• Published: 07/30/2009
• Est. Priority Date: 03/28/2002
• Status: Active Grant

• 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
• Granted Patent: US 8,126,709 B2
• Time in Patent Office: Days
• US Class Current: 704/500
• 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 for generating a reconstructed signal that comprises:

receiving a signal containing data representing a baseband signal derived from an audio signal 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;

obtaining a regenerated signal comprising regenerated spectral components by copying into individual subbands the lowest-frequency baseband spectral components to a lower edge of a respective subband and continuing through the baseband spectral components in a circular manner to complete a translation for that respective subband; and

obtaining a time-domain representation of the reconstructed signal corresponding to a combination of the baseband spectral components, the regenerated spectral components and the estimated spectral envelope.

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

3. The method of claim 1 that comprises applying a time-domain aliasing cancellation synthesis transform to obtain the time-domain representation of the reconstructed signal.

4. The method of claim 1 that comprises adapting the copying of spectral components by changing which spectral components are copied or by changing the frequency amount by which spectral components are copied.

5. The method of claim 1, wherein the data contained in the received signal also represents a noise-blending parameter derived from a measure of noise content of the audio signal, and wherein the method comprises adjusting amplitudes of the regenerated spectral components according to the estimated spectral envelope and the noise-blending parameter.

6. 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 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 obtaining a regenerated signal comprising regenerated spectral components by copying into individual subbands the lowest-frequency baseband spectral components to a lower edge of a respective subband and continuing through the baseband spectral components in a circular manner to complete a translation for that respective subband; and

means for obtaining a time-domain representation of the reconstructed signal corresponding to a combination of the baseband spectral components, the regenerated spectral components and the estimated spectral envelope.

7. The apparatus of claim 6, wherein the time-domain representation of the reconstructed signal is obtained to represent segments of the reconstructed signal that vary in length.

8. The apparatus of claim 6 that comprises means for applying a time-domain aliasing cancellation synthesis transform to obtain the time-domain representation of the reconstructed signal.

9. The apparatus of claim 6 that comprises means for adapting the copying of spectral components by changing which spectral components are copied or by changing the frequency amount by which spectral components are copied.

10. The apparatus of claim 6, wherein the data contained in the received signal also represents a noise-blending parameter derived from a measure of noise content of the audio signal, and wherein the apparatus comprises means for adjusting amplitudes of the regenerated spectral components according to the estimated spectral envelope and the noise-blending parameter.

11. A storage 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 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;

obtaining a regenerated signal comprising regenerated spectral components by copying into individual subbands the lowest-frequency baseband spectral components to a lower edge of a respective subband and continuing through the baseband spectral components in a circular manner to complete a translation for that respective subband; and

obtaining a time-domain representation of the reconstructed signal corresponding to a combination of the baseband spectral components, the regenerated spectral components and the estimated spectral envelope.

12. The medium of claim 11, wherein the time-domain representation of the reconstructed signal is obtained to represent segments of the reconstructed signal that vary in length.

13. The medium of claim 11, wherein the method comprises applying a time-domain aliasing cancellation synthesis transform to obtain the time-domain representation of the reconstructed signal.

14. The medium of claim 11, wherein the method comprises adapting the copying of spectral components by changing which spectral components are copied or by changing the frequency amount by which spectral components are copied.

15. The medium of claim 11, wherein the data contained in the received signal also represents a noise-blending parameter derived from a measure of noise content of the audio signal, and wherein the method comprises adjusting amplitudes of the regenerated spectral components according to the estimated spectral envelope and the noise-blending parameter.