Apparatus and Method for Generating an Output Audio Data Signal

• US 20120116560A1
• Filed: 04/01/2010
• Published: 05/10/2012
• Est. Priority Date: 04/01/2009
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola Mobility, Inc. (Lenovo Group Ltd.)
• Inventors: Francois, Holly, Gibbs, Jon.
• Granted Patent: US 9,230,555 B2
• Time in Patent Office: Days
• US Class Current: 700/94
• CPC Class Codes: G10L 19/24 Variable rate codecs, e.g. for generating different qualities using a scalable representation such as hierarchical encoding or layered encoding

Abstract

An apparatus receives an input encoded audio data signal comprising a base layer and at least one enhancement layer. A reference unit (103) generates reference audio data corresponding to audio data of a reference set of layers. A layer unit (105) divides the layers of the input signal into a first subset and a second subset. A sample unit (107) generates sample audio data corresponding to the audio data of the first subset. A comparison unit (109) generates a difference measure by comparing the sample audio data to the reference audio data based on a perceptual model. An output unit (111) then determines if the difference measure meets a similarity criterion and generates an output signal without audio data from a layer of the second subset if the similarity criterion is met and including the audio data of the layer otherwise. The invention may provide reduced data rates without an unacceptable degradation of quality.

Claims

1. An apparatus for generating an output audio data signal, the apparatus comprising:

means for receiving an input encoded audio data signal comprising a plurality of encoding layers including a base layer and a plurality of enhancement layers;

reference means for generating reference audio data from a reference set of layers of the plurality of encoding layers;

sample means for generating sample audio data from a set of layers smaller than the reference set of layers;

difference means for comparing the sample audio data to the reference audio data, the comparison reflecting a difference between a first decoded signal corresponding to the sample audio data and a second decoded signal corresponding to the reference audio data;

output means for determining whether the comparison meets a criterion and

if so, generating the output audio data signal to not include audio data from a first layer, the first layer being a layer of the reference set not included in the smaller set of layers;

and otherwise, generating the output audio data signal to include audio data from the first layer.

2. The apparatus of claim 1 wherein the reference audio data corresponds to a frequency domain representation of an audio signal represented by the audio data of layers of the reference set, and the sample audio data corresponds to a frequency domain representation of an audio signal represented by the audio data of layers of the smaller set of layers.

3. The apparatus of claim 2 wherein the frequency domain representation is an internal frequency domain representation of an encoding protocol of the input encoded audio data signal.

4. The apparatus of claim 1 arranged to generate the output audio data from a minimum number of layers required in the smaller set of layers for the comparison to meet the criterion.

5. The apparatus of claim 1 wherein the comparison is based on a perceptual model.

6. The apparatus of claim 5 wherein the difference means comprises:

means for generating a first perceptual indication by applying the perceptual model to the reference audio data;

means for generating a second perceptual indication by applying the perceptual model to the sample audio data; and

the output means is arranged to determine whether the comparison meets the criterion in response to a comparison of the first perceptual indication and the second perceptual indication

7. The apparatus of claim 6 wherein the perceptual model consists in:

determining an energy measure for each of a plurality of critical bands;

applying a loudness compensation to the energy measure of each of the plurality of critical bands to generate a perceptual indication comprising loudness compensated energy measures for each of the critical bands; and

the output means is arranged to determine whether the comparison meets the criterion in response to a comparison of the loudness compensated energy measures for each of the critical bands for the reference audio data and the sample audio data.

8. The apparatus of claim 7 wherein the loudness compensation comprises determining a loudness compensated energy measure for a critical band as a function of:

9. The apparatus of claim 1 wherein:

the reference means is arranged to generate the reference audio data as a time domain audio signal by decoding the audio data of the reference set of layers; and

the reference means is arranged to generate the sample audio data as a time domain audio signal by decoding the audio data of the first subset of layers.

10. The apparatus of claim 1 wherein output means is arranged to generate the output audio data signal to include audio data from all layers of the plurality of encoding layers if the comparison does not meet the criterion.

11. The apparatus of claim 1 wherein the base layer comprises parametrically encoded speech data based on a speech model, and at least one layer of the reference set of layers not included in the smaller set of layers comprises waveform encoded audio data.

12. The apparatus of claim 1 wherein input encoded audio data signal is encoded in accordance with an International Telecommunication Union Telecommunication Standardization Sector, ITU-T, G.718 protocol.

13. A communication system including a network entity which comprises:

means for receiving an input encoded audio data signal comprising a plurality of encoding layers including a base layer and a plurality of enhancement layers;

reference means for generating reference audio data from a reference set of layers of the plurality of encoding layers;

sample means for generating sample audio data from a set of layers smaller than the reference set of layers;

difference means for comparing the sample audio data to the reference audio data, the comparison reflecting a difference between a first decoded signal corresponding to the sample audio data and a second decoded signal corresponding to the reference audio data;

output means for determining whether the comparison meets a criterion and

if so, generating the output audio data signal to not include audio data from a first layer, the first layer being a layer of the reference set not included in the smaller set of layers;

and otherwise, generating the output audio data signal to include audio data from the first layer.

14. The communication system of claim 13 wherein the network entity is a Radio Access Network network element of a cellular communication system.

15. The communication system of claim 14 further comprising means for allocating an air interface resource in response to a set of layers included in the output audio data signal.

16. A method for generating an output audio data signal, the method comprising:

receiving an input encoded audio data signal comprising a plurality of encoding layers including a base layer and a plurality of enhancement layers;

generating reference audio data from a reference set of layers of the plurality of encoding layers;

generating sample audio data from a set of layers smaller than the reference set of layers;

comparing the sample audio data to the reference audio data, the comparison reflecting a difference between a first decoded signal corresponding to the sample audio data and a second decoded signal corresponding to the reference audio data;

determining whether the comparison meets a criterion and

if so, generating the output audio data signal to not include audio data from a first layer, the first layer being a layer of the reference set not included in the smaller set of layers;

and otherwise, generating the output audio data signal to include audio data from the first layer.