Audio processing

• US 20060025993A1
• Filed: 06/18/2003
• Published: 02/02/2006
• Est. Priority Date: 07/08/2002
• Status: Abandoned Application

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips N.V.
• Inventors: Aarts, Ronaldus Maria, Schobben, Daniel Willem Elisabeth, Sheik Soeltan, Faizal
• Application Number:
  US10/520,201
• Publication Number:
  US 20060025993A1
• Time in Patent Office: Days
• US Class Current: 704/228
• CPC Class Codes: H04S 1/007 in which the audio signals are in digital form data reduction aspects thereof based on psychoacoustics G10L19/02

Abstract

An audio system comprises a post-processor (12) arranged to alter successive fragments of a decoded audio signal (14) to provide successive fragments of post-processed audio signal (16). A masking threshold generator (20) provides an estimate of a masking threshold ( ) for successive fragments of post-processed audio signal (16). A noise level generator (17) provides an estimate of a noise level ( ) for successive fragments of the post-processed audio signal (16). A distortion generator (17) determines a degree (D) to which the noise level exceeds the masking threshold for successive fragments of the post-processed audio signal (16). A regulator (18) controls the post-processor according to the degree to which the noise levels exceed the masking threshold.

Claims

1. An audio system comprising:

a post-processor arranged to alter successive fragments of a decoded audio signal to provide successive fragments of post-processed audio signal;

a distortion detector for determining a degree to which quantization noise introduced in encoding said successive fragments of audio signal becomes audible due to said post-processing; and

a regulator arranged to control said post-processor according to said degree.

2. An audio system as claimed in claim 1 further comprising:

a masking threshold generator arranged to provide an estimate of a masking threshold for said successive fragments of post-processed audio signal;

a noise level detector arranged to provide an estimate of a noise level for said successive fragments of said post-processed audio signal;

and wherein said distortion detector determines said degree according to the degree to which said noise level exceeds said masking threshold for successive fragments of said post-processed audio signal.

3. An audio system as claimed in claim 2 further comprising a decoder arranged to read an audio stream and to produce said successive fragments of audio signal.

4. An audio system as claimed in claim 3 wherein said decoder produces stereo-encoded successive pairs of fragments of audio signal and said post-processor applies stereo-widening to said successive pairs of fragments of audio signal.

5. An audio system as claimed in claim 2 wherein said masking threshold generator comprises a psycho-acoustic modeling component arranged to transform said successive fragments of post-processed audio signal into the frequency domain;

and to derive said masking threshold therefrom.

6. An audio system as claimed in claim 2 wherein said masking threshold generator comprises a psycho-acoustic modeling component arranged to read said audio stream and to produce successive fragments of audio signal;

to apply similar post-processing to said successive fragments of audio signal as said post-processor;

to transform said successive post-processed fragments of audio signal into the frequency domain; and

to derive said masking threshold from said post-processed signal.

7. An audio system as claimed in claim 2 further comprising an inverse decoder arranged to read said successive fragments of a decoded audio signal and to provide therefrom indications of quantization levels employed in the encoding of an audio stream from which said audio signal is decoded.

8. An audio system as claimed in claim 3 in which said noise level detector is arranged to derive from said audio stream quantization levels employed in the encoding of an audio stream.

9. An audio system as claimed in claim 7 in which said noise level detector is arranged to derive from said quantization levels a distribution of noise level in the frequency domain for said successive fragments of a decoded audio signal, and to apply similar post-processing to said successive distributions of noise level as said post-processor to provide successive estimates of noise level for said successive fragments of said post-processed audio signal.

10. A method of processing an audio stream comprising the steps of:

post-processing successive fragments of a decoded audio signal to provide successive fragments of post-processed audio signal;

detecting a degree to which quantization noise introduced in encoding said successive fragments of audio signal becomes audible due to said post-processing; and

regulating said post-processing step according to said degree.