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Error concealment for sub-band coded audio signals

An audio signal, encoded technology, applied in the direction of forward error control, speech analysis, code conversion, etc., to achieve the effect of reducing unnecessary waste

Active Publication Date: 2012-05-30
NXP BV
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] Known repetition and replacement techniques have the disadvantage that the receiver requires (additional) data memory to store (adjacent in time) , or from other stereo channel) decoded frames

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  • Error concealment for sub-band coded audio signals
  • Error concealment for sub-band coded audio signals
  • Error concealment for sub-band coded audio signals

Examples

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Embodiment Construction

[0049] The MPEG Audio Layer II audio codec used in DAB is a subband codec. Compression is performed in the time domain using a filter bank that generates 32 equally spaced subbands with a bandwidth of 750 Hz at a sampling rate of 48 kHz. All these subbands are not equally perceptually correlated. The first sub-band covers the bandwidth from 0 Hz (DC) to 750 Hz, which corresponds to the 8 critical bands of the human auditory system, while the second sub-band covers only 4 critical bands.

[0050] Isolated bit errors in subbands produce time-domain discontinuities that can typically be heard as band-limited "click" noise. Bursts of bit errors tend to randomize the time-domain signal of the corrupted subbands, which can be heard as band-limited white noise.

[0051] The inventors have observed that these artifacts are most annoying in the first sub-band ranging from 0 to 750 Hz. This is not only due to the relatively low frequency resolution of the MPEG Audio Layer II filterba...

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Abstract

A decoder and method of decoding a sub-band coded digital audio signal are disclosed. The decoder comprises: an input, for receiving sub-band coefficients for a plurality of sub-bands of the audio signal; an error detection unit (20), adapted to analyze the content of a sequence of coefficients in one of the sub-bands, to derive for each coefficient an indication of whether the coefficient has been corrupted by an error of a predefined type; an error masking unit (30), adapted to generate from the sequence a modified sequence of coefficients for the sub-band, wherein errors of the predefined type are attenuated; a coefficient combination unit (40), adapted to combine the received coefficients and the modified coefficients, in dependence upon the indication of error; and a signal reconstruction unit (50), adapted to reconstruct the audio signal using the combined coefficients.

Description

technical field [0001] The present invention relates to a method and apparatus for concealing errors in a received digital audio signal that has been coded using a subband coding (SBC) scheme. In particular, it relates to a DAB receiver implementing a source decoder according to the MPEG-1 Audio Layer II (MP2) standard defined in ISO / IEC 11172-3. Background technique [0002] Digital Audio Broadcasting (DAB) receivers are subject to harsh transmission conditions especially in mobile and automotive environments. Although the channel decoder includes several error correction schemes, residual bit errors cannot be completely avoided. [0003] Frame-level concealment techniques that mask the effects of such bit errors are well known in the art. A simple example is to mute the output for the duration of an audio frame in which an error is detected. Another possibility is repetition, where adjacent frames are used instead of frames containing bit errors. If the stream includes...

Claims

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Application Information

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IPC IPC(8): G10L19/00G10L19/005G10L19/02
CPCG10L19/005H04L1/0072G10L19/0204H03M7/3046
Inventor 克里斯托弗・马克・马库斯
Owner NXP BV
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