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Signal filtering

A signal and filter technology, applied in electronic editing of digitized analog information signals, speech analysis, instruments, etc., can solve the problems of complex LTP filtering and large filter order

Active Publication Date: 2020-08-25
FRAUNHOFER GESELLSCHAFT ZUR FOERDERUNG DER ANGEWANDTEN FORSCHUNG EV
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, such methods are too complex for LTP filtering, since the number of non-zero reflection coefficients would be equal to the pitch lag (for example, if used to smooth LTP discontinuities in [3], this would result in a filter order greater than 250)

Method used

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Embodiment Construction

[0125] In the method presented here, the filtering parameters (also referred to as filter parameters or parameters) generally differ for different update intervals. Two consecutive update intervals may have different parameters. In an example, the update interval may be signal adaptive and its length may be changed or shifted over time.

[0126] In some examples, the signal is divided into frames. For example, a frame may be associated with a fixed number of samples and / or a fixed length of time (eg, 20ms). When transmitted or stored, frames can be associated with specific parameters, eg filtering parameters. Within the same frame, the parameters may be substantially constant.

[0127] In some examples, the update interval may correspond to frames. Thus, when transmitted or stored, a signal may eg be encoded with data associated with a particular frame, including parameters (eg filter parameters) associated with the frame (which is also the update interval).

[0128] In s...

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Abstract

There are discussed methods and systems for filtering an information input signal (11, 11a, x), divided into different update intervals, according to parameters varying with the update intervals, to obtain a filtered output signal (y, 15). A system (10) may comprise: - a first filter unit (12) to filter a first filter input signal (11, x) at least at an initial subinterval (T i ) in a current update interval (T) to obtain a first filter output signal (y', 13), according to parameters associated to the preceding update interval, the first filter unit (12) being configured to change the parameters along at least the initial subinterval (T i ) from a higher-filtering status to a lower-filtering status; and - a second filter unit (14) to filter a second filter input signal (13), at the initialinterval (T i ), according to parameters associated to the current update interval (T) to obtain a second filter output signal (15), the second filter unit (14) being configured to change the parameters along at least the initial subinterval (T i ) from a lower-filtering status to a higher-filtering status. The first filter input signal (11) is based on the information input signal (x), the firstfilter output signal (13) is an intermediate signal (y'), the second filter input signal is based on the intermediate signal (y'), and the filtered output signal (y) is based on the second filter output signal (15).

Description

technical field [0001] Examples of the invention relate to systems and methods for filtering signals (eg, LTP post-filtering and / or pre-filtering). Background technique [0002] The prior art includes the following publications: [0003] [1] A.T.Hill and A.Ilchmann, "Exponential stability of time-varying linear systems," IMA J Numer Anal, pp.865-885, 2011. [0004] [2] 3GPP TS 26.090, Adaptive Multi-Rate (AMR) speech codec; Transcodingfunctions (Adaptive Multi-Rate (AMR) speech codec; transcoding function). [0005] [3] 3GPP TS 26.445, Codec for Enhanced Voice Services (EVS); Detailed algorithm description (codec for Enhanced Voice Services (EVS); detailed algorithm description). [0006] [4] 3GPP TS 26.190, Adaptive Multi-Rate-Wideband (AMR-WB) speech codec; Transcoding functions (Adaptive Multi-Rate-Wideband (AMR-WB) speech codec; transcoding function). [0007] [5] 3GPP TS 26.290, Extended Adaptive Multi-Rate-Wideband (AMR-WB+) codec; Transcoding functions (Extended Ad...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G10L19/26H03H17/02G10L19/04G10L19/00G10L19/09
CPCG10L19/04G10L2019/0012G10L19/26G10L19/09H03H17/0294H03H2017/0295H03H17/02G11B27/038G10L19/22
Inventor 戈兰·马尔科维奇伊曼纽尔·拉维利马丁·迪茨伯恩哈特·格里尔
Owner FRAUNHOFER GESELLSCHAFT ZUR FOERDERUNG DER ANGEWANDTEN FORSCHUNG EV