CN1993734A - Noise suppression process and device - Google Patents
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Abstract
A noise suppression process (S_OUT) for a decoded signal comprising a first decoded signal portion (S_CELP) and a second decoded signal portion (S TDAC) has the following steps: determining a first energy envelope generating curve (ENV_CELP) of the first signal portion (S_CELP) and a second energy envelope generating curve (ENV_TDAC) of the second decoded signal portion (S_TDAC); forming an identification number (R) depending on a comparison of the first and second energy envelope generating curves (ENV_CELP, ENV_TDAC); deriving an amplification factor (G) which depends on the identification number (R); advantageously multiplying the second decoded signal portion by the amplification factor, which leads to the desired reduction of pre-echo and post-echo interference noises.
Description
The present invention relates to a kind of method that is used for decoded signal, this signal is encoded by hybrid coder.In addition, the invention still further relates to a kind of equipment that is used to decode of relative configurations.
For coding audio signal, diverse ways has turned out to be effective especially.Therefore, for example encode well and have the voice signal of better quality for quality, and under the situation of low bit rate, particularly so-called CELP technology (Code Excited Linear Prediction (Code Excited Linear Prediction)) proves favourable in data encoded stream.CELP is operated in time domain and based on the excitation of variable wave filter.In this case, not only represented voice signal by filter parameter but also by the parameter of describing pumping signal.
Also mention corresponding demoder aspect scrambler mostly, this demoder is decodable code or decoding data encoded again.Corresponding communication facilities has this so-called codec, so that can transmit and receive data, this is essential for communication.
Even also should have very high-quality music signal and voice signal for the bit rate of the stream of data encoded particularly of encoding is higher, so-called sensation codec (codec=encoder/decoder) at first is achieved.These sensation codecs reduce based on the information in the frequency domain, and these sensation codecs make full use of human auditory system's shielding effect, that is to say, for example also do not represent some frequency or the variation that the mankind can not feel.Thus, reduced the complexity of scrambler or codec.Because the most utilization of scrambler transforms to frequency domain with time signal and comes work, wherein for example (conversion is carried out in the discrete cosine transform of modification (Modified Discrete Cosine Transformation), so these scramblers often are also referred to as transform coder or transform coding and decoding device by MDCT.This expression also is used in the scope of other application.
Recently, adopt so-called scalable (Skalierbar) codec more and more.Scalable codec is this codec, and these codecs at first produce fabulous audio quality when the bit rate of data encoded stream is high relatively.Obtained long, that want cyclical transmission relatively packet thus.
Packet is a mass data, and these data occurred with a time interval, and these data are just in time transmitted with this packet together.In packet, often at first transmit important data and then transmit time important data., in long packet, there is following possibility, promptly shortens packet by removing a part of data, particularly the part of last transmission in time by the truncated data bag.The deterioration of quality appears naturally thereupon.
Because above-mentioned characteristic is suitable for for scalable codec, when bit rate is low, utilizes the work of CELP codec and when bit rate is higher, utilize the work of transform coding and decoding device.This has caused the development of mixed C ELP/ transform coding and decoding device, these mixed C ELP/ transform coding and decoding device has the baseband signal of better quality according to the CELP coding, and in addition generate auxiliary signal, utilize this auxiliary signal to improve baseband signal according to the transform coding and decoding method.Then, this causes desirable fabulous quality.
When using the transform coding and decoding device disadvantageously, so-called " Pre echoes effect " appears.Relate to interference noise at this, this interference noise is evenly distributed on the whole block length of transform coder piece." piece " is understood that all data of being encoded jointly.For the transform coding and decoding device, typical block length is 40msec.The interference noise of Pre echoes effect forms by the quantization error of institute's transmission frequency spectra component.Under the uniform situation of signal level, the level of interference noise all is lower than the level of useful signal.But,, before adopting high level, can hear this interference noise significantly so if unexpected high level is being followed the useful signal of zero level.In the literature, be that signal when the clatter of Castanette click rings changes to this known example.
In order to reduce these effects, used diverse ways.But these methods all utilize the transmission supplementary to come work, and this constructs encoder design very complicated again or forces scrambler to come work with the bit rate that temporarily is enhanced.
From prior art, task of the present invention provides a kind of simple possibility, causes carrying out interference noise and reduce in the signal that is encoded by hybrid coder, wherein needn't supplementary.
This task solves by the theme of independent claims.Favourable expansion scheme is the theme of dependent claims.
Reduce in the decoded signal that by first, for example from the signal and second of CELP demoder, for example comes the signal of transformation into itself's demoder to form, carrying out interference noise, carry out following steps:
Determine affiliated energy envelope line respectively according to two decoded signal sections." energy envelope line " particularly is understood that the energy distribution of signal relative time.
Identification number (Kennzahl), for example ratio have relatively been constituted by these two envelopes.
Identification number is used to derive amplification factor again.
If energy is for example identified reliably in the coding method that causes the first decoded signal section, then this method particularly has advantage.Therefore, that is by identification number or amplification factor discern deviation.
Particularly, second decoded signal section and the amplification factor multiplies each other.Mentioned deviation above proofreading and correct thus.
Divide whole signal with the time interval, the time interval that wherein particularly is used to the first decoded signal section is shorter than the time interval of secondary signal part.
Thus, can proofread and correct energy deviation in the secondary signal part better according to higher temporal resolution.
First signal section can be from the CELP demoder, this CELP decoder decode CELP encoded signals, and the secondary signal part can be come transformation into itself's demoder, and this conversion decoder decode is transformed encoded signals.Be transformed that encoded signals particularly also can comprise first, the signal section of CELP decoding, this first, the signal section of CELP decoding is transformed coding after decoding, be added to transmit by transmitter be transformed encoded signals (promptly in frequency), and then in the conversion demoder, be decoded as the part of secondary signal part.
To this replacedly, also in time domain, carry out by CELP encoded signals of being transmitted and the summation of being transmitted that is transformed encoded signals.
Particularly, amplification factor can equal identification number.Therefore, if the second decoded signal section particularly comprises the Pre echoes noise, then when constituting suitable ratio, can obtain second decoded the corresponding of signal section and weaken.
Particularly, first demoder is based on the demoder of CELP technology, and/or second scrambler is the conversion demoder.Thus, obtaining special effective noise under the simultaneously fabulous situation of the quality of decoded signal reduces.
Particularly, have only when having some criterion, then just carry out the change of the whole signal that is received of decoder-side.
Particularly regulation has only when signal level variation surpasses a certain threshold value, just carries out the change of the whole signal that is received of decoder-side.This has realized reducing especially effectively Pre echoes, because this Pre echoes effect (as described) occurs when level changes fully, because then the Pre echoes noise is positioned on the signal level.On the other hand, by changing selectively rather than unnecessarily abandoning improving quality by second scrambler.
According to a further aspect in the invention, provide a kind of method, wherein based on the method for being set forth, according to first and second of the decoded signal of frequency domain separate processes or this signal decoded signal sections.This has the following advantages.In when decoding, for the rated energy of known this frequency band of a plurality of frequency bands, i.e. the rated energy that constitutes by the energy of the single first decoded signal section (for example CELP signal) that separates according to frequency domain.Can provide additional signal (slave part) now by the second decoded signal section, but this additional signal can depart from greatly on its energy.At first, if the energy of the second decoded signal section then is problematic for example because the Pre echoes effect is obviously too high.Now, for each single processed frequency band, this method introduce with the energy of first signal section relatively to the restriction of the energy (or level) of secondary signal part.Many more frequency bands are separate processes by this way, and then this method is just effective more.
Other advantage of the present invention is described with reference to exemplary form of implementation.
Wherein:
Fig. 1 shows the figure of the critical piece of coder side and decoder-side for the example process of setting forth the coding/decoding process;
Fig. 2 shows the synoptic diagram that is used for transmitting by communication network the communicator of the signal that is encoded between communication facilities;
Fig. 3 to reduce Pre echoes and shows decoding device or noise suppression device in order to set forth by the gain adaptation (Gain-Adaption) based on the CELP signal;
Fig. 4 shows and is used to other form of implementation of carrying out level match or being used to reduce Pre echoes.
In Fig. 1, show the illustrative process of cataloged procedure and decode procedure with reference to form of implementation.At coder side C, the signal S that be transferred to receiver of simulation is by pretreated or be prepared at the pre-processing device PP of coding, and for example its mode is with this signal S digitizing.In addition, also in division unit F, split signal with the time interval or frame.Preparative is fed to coding unit COD like this.Coding unit COD has hybrid coder, and this hybrid coder comprises first scrambler (being celp coder) COD1 and second scrambler (being transform coder) COD2.Celp coder COD1 comprises a plurality of celp coder COD1_A, COD1_B, COD1_C, and these celp coders are in different frequency domain work.By being divided into different frequency domains, can guarantee coding especially accurately.In addition, be divided into the notion that different frequency domains is also supported scalable codec very goodly, because can be transmitted according to desirable flexible only one, a plurality of or all frequency domains.Celp coder COD1 provides the essential part S_G of the whole signal S_GES that is encoded.Transform coder COD2 provides the slave part S_Z of the whole signal S_GES that is encoded.The whole signal S_GES that is encoded is transferred to the communication facilities KD of decoder-side D by the communication facilities KC of coder side C.At this, in treatment facility PROC, data or the whole signal S_GES that is encoded that received are handled (the whole Signal Separation that for example will be encoded becomes part S_G and S_Z) in case of necessity, wherein follow processed data or processed signal and be transferred to decoding device DEC and be used to carry out subsequently decoding DEC (to this also referring to Fig. 3 and 4).Noise reduction among the noise reducing apparatus NR is right after after decoding, and this noise reducing apparatus NR is illustrated in Fig. 3 in more detail.
In Fig. 2, show the first communication facilities COM1 (for example being the parts on the coder side C of Fig. 1 typically), this first communication facilities COM1 has transmission and receiving element ANT1 (for example corresponding to communication facilities KC) and the computing unit CPU1 that is used to transmit and/or receive data, and this computing unit CPU1 is set up to be used to realize the parts on the coder side C or to be used for the coding method shown in the execution graph 1 (in the processing of coder side C).Carry out data transmission by transmission/receiving element ANT1 by communication network CN (this communication network CN for example can be established as the Internet, telephone network or mobile radio telephone according to the communication facilities that will use).Receive by second communication equipment COM2 (for example being the right-hand side assembly of Fig. 1 typically), this second communication equipment COM2 has again and sends and receiving element ANT2 (for example corresponding to communication facilities KB) and computing unit CPU2, and this computing unit CPU2 is used to realize the parts on the decoder-side D by setting up or is used to carry out coding/decoding method (in the processing of decoder-side D) according to Fig. 1.The example of using the possible implementation of the communication facilities COM1 of this method and COM2 therein is IP phone, voice gateways or mobile phone.
Consult Fig. 3 now, wherein the process that reduces for schematically illustrated Pre echoes can be seen decoding device DEC and the noise reducing apparatus NR with critical piece.CELP encoded signals S_COD, CELP (corresponding to signal S_G) is by whole frequency band CELP demoder DEC_GES, and CELP decodes.Decoded signal S_CELP is forwarded to the energy envelope line determining unit GE1 of the envelope ENV_CELP under being used for determining on the one hand, and is forwarded to TDAC (time domain obscure offset (Time domain aliasing cancellation)) scrambler COD_TDAC on the other hand.The TDAC coding is the example of transition coding.
The signal S_COD that is encoded, CELP, TDAC with from receiver-side be transformed encoded signals S_COD, TDAC (corresponding to signal S_Z) is directed to conversion demoder DEC_TDAC together, so that produce decoded signal S_TDAC.Energy envelope line ENV_TDAC under also in (second) energy envelope line determining unit GE2, determining equally according to decoded signal S_TDAC.In ratio determining unit D, the ratio R of energy envelope line is confirmed as to the time interval identification number mutually one by one.Determine in condition determining unit BFE whether ratio R has definite minimum spacing 1 (1: two energy envelope line equates), that is to say that the level of two signals equates or the predetermined percentage of mutual at least only deviation.
Therefore, the result is amplification factor or attenuation factor G, this amplification factor or attenuation factor G shown in situation under equal ratio R (identification number), the signal section S_TDAC that is transformed decoding multiplies each other with this ratio R in multiplication equipment M, so that obtain the signal S_OUT that final interference noise reduces.More precisely, for example set out thus, promptly come composition R by R=ENV_CELP/ENV_TDAC, and determined, this ratio does not allow to be lower than predetermined threshold value SW, therefore when being lower than threshold value SW, the signal section S_TDAC and the amplification factor G (for example G=R) that are transformed decoding multiply each other, and this causes the decay of signal section S_TDAC.In addition, possible is, under the situation that is not less than threshold value SW, will be worth " 1 " and distribute to amplification factor G, so that when the multiplying each other of then under any circumstance generable signal section S_TDAC, value S_TDAC remains unchanged.
Therefore, under the situation of the energy that departs from the signal section S_TDAC that is transformed decoding, the described just Pre echoes effect of this deviation wherein, the energy of signal section or level move to the reliable value of the signal S_CELP of CELP decoding, so that carry out interference noise for final signal S_out and reduce.
Consult Fig. 4 now, should set forth other form of implementation that is used to reduce the Pre echoes effect according to this figure.
Possible is, only replace a CELP codec and exist a plurality of, according to frequency domain separated (CELP-or other) codec.Most of corresponding with the form of implementation shown in Fig. 3 and be a kind of expansion thus in the form of implementation shown in Fig. 4, be not the whole signal that is applied to CELP (perhaps other) demoder and conversion demoder promptly, but this method is used according to frequency domain dividually in the method shown in Fig. 3.That is to say, at first divide whole signal or individual signals part according to frequency domain, wherein the method for Fig. 3 then is applied to the individual signals part to each frequency domain.
Below set forth its advantage.In demoder, for the rated energy of known these frequency bands of a plurality of frequency bands, that is the rated energy that constitutes by the energy of the single CELP signal that separates according to frequency domain.Now, the conversion demoder provides additional signal (slave part), and, this additional signal is departing from aspect its energy significantly.At first, if the energy of signal that comes transformation into itself's demoder is for example because Pre echoes effect and obviously too high then is problematic.Now, for the frequency band of each single processing, this method introduce with the CELP energy relatively to the restriction of transform coding and decoding device energy.Multiband is separately processed by this way more, and then this method is just effective more.
This becomes obvious immediately according to following example:
Whole signal is made of the 2000Hz tone, and this whole signal is fully from CELP codec part.In addition, because the Pre echoes effect, it is the undesired signal of 6000Hz that the transform coding and decoding device now only also provides frequency; The energy of undesired signal be the 2000Hz tone energy 10%.Being used to limit transform coding and decoding device criterion partly is, it is identical with the maximal value of CELP part that the maximal value of transform coding and decoding device part allows.Situation 1: do not carry out the decomposition (first embodiment) according to frequency band: then, the 6000Hz undesired signal is not suppressed, because this undesired signal is only from 10% of the energy of the 2000Hz tone of CELP codec.
Situation 2: frequency band A:0-4000Hz and B:4000Hz-8000Hz processed dividually (other form of implementation): in this case, undesired signal is suppressed fully, because in the superincumbent frequency band, CELP partly is zero, and therefore also that transform coding and decoding device signal limitations is zero to value.
(corresponding to Fig. 3) is in Fig. 4, for the process of schematically illustrated level match or Pre echoes reduction can be seen decoding device DEC and the noise reducing apparatus NR with critical piece again now.In order to produce the signal that is encoded or to be transferred to receiver again with reference to figure 1 or 2.
CELP encoded signals S_COD, CELP (corresponding to signal section S_G) is by whole frequency band CELP demoder DEC_GES, and CELP ' decodes.Whole frequency band CELP demoder comprises two decoding devices at this, the decode signal S_COD of the second frequency band B of the signal S_COD of the first frequency band A that promptly is used for decoding, the first decoding device DEC_FB_A of CELP and being used for, the second decoding device DEC_FB_B of CELP.The first decoded signal S_CELP_A is directed to (first) energy envelope line determining unit GE1_A of the envelope ENV_CELP_A under being used for determining, and the second decoded signal S_CELP_B is directed to (second) energy envelope line determining unit GE1_B of the envelope ENV_CELP_B under being used for determining.
From receiver-side be transformed encoded signals S_COD, TDAC (corresponding to signal S_Z) is directed to conversion demoder DEC_TDAC so that produce decoded signal S_TDAC, this signal S_TDAC is fed to band-splitter (frequency band division device) FBS again.This band-splitter FBS is divided into two signals with signal S_TDAC, that is is divided into the S_TDAC_A of frequency band A and the S_TDAC_B of frequency band B.Alternatively, be divided into frequency band and also can in frequency domain, carry out, before time domain, carry out in inverse transformation.Thus, particularly cancelled the delay that occurs along with the band-splitter of in time domain, working (Hi-pass filter, low-pass filter or bandpass filter).In (the 3rd) energy envelope line determining unit GE2_A or (the 4th) energy envelope line determining unit GE2_B, determine affiliated energy envelope line ENV_TDAC_A or ENV_TDAC_B too according to decoded signal S_TDAC_A relevant and S_TDAC_B with frequency band.
Amplify among the determining unit BD_A first, determine amplification factor (perhaps also definite attenuation factor for frequency band A according to energy envelope line ENV_CELP_A and ENV_TDAC_A, because be enlarged into negative) G_A is determined, and amplify among the determining unit BD_B second, determine amplification factor (attenuation factor) G_B for frequency band B according to energy envelope line ENV_CELP_B and ENV_TDAC_B.The definite of corresponding amplification factor can (referring to parts D, BFE) carry out according to the definite of Fig. 3.At this, for example can constitute corresponding proportion (identification number) R_A, R_B again for the energy envelope line of frequency band corresponding A and B, that is R_A=ENV_CELP_A/ENV_TDAC_A or R_B=ENV_CELP_B/ENV_TDAC_B, wherein determine threshold value SW_A or SW_B for frequency band corresponding, when being lower than threshold value, produce corresponding amplification factor G_A (for example G_A=R_A) or G_B (for example G_B=R_B), this amplification factor G_A or G_B are used to corresponding signal S_TDAC_A relevant with frequency band or S_TDAC_B (so that causing decay) at last.If be not lower than corresponding threshold value, then corresponding amplification factor G_A or G_B are confirmed as " 1 ", so that when multiplying each other, corresponding signal S_TDAC_A or the S_TDAC_B relevant with frequency band remains unchanged.
In the first multiplication equipment M_A of frequency band A, at last amplification factor G_A and signal S_TDAC_A are multiplied each other and amplification factor G_B and signal S_TDAC_B are multiplied each other.At last, the signal that (may decay) of multiplying each other is relevant with frequency band is assembled, so that realize (whole frequency) signal S_OUT ' that final interference noise reduces.
It should be noted that,, also can be divided into 3 or multifrequency territory more, and also be favourable although only carried out in the present example decoded signal section S_CELP_A, S_CELP_B, S_TDAC_A and S_TDAC_B are separated into two frequency domain A and B.
Claims (15)
1. method that is used for carrying out squelch (S_OUT) at decoded signal, described decoded signal is made up of the first decoded signal section (S_CELP) and the second decoded signal section (S_TDAC), and described method has following steps:
A. determine first energy envelope line (ENV_CELP) of first signal section (S_CELP) and the second energy envelope line (ENV_TDAC) of the second decoded signal section (S_TDAC);
B. according to the first and second energy envelope lines (ENV_CELP, ENV_TDAC) relatively constitute identification number (R);
C. derive amplification factor (G) according to described identification number (R).
2. method according to claim 1 has following other step:
If d. described identification number (R) does not satisfy determined criterion (C), then the described second decoded signal section (S_TDAC) is multiplied each other with described amplification factor (G).
3. one of require described method according to aforesaid right, wherein, described decoded signal section (S_TDAC S_CELP) divides with the time interval, and carries out described step a) to d to the time interval one by one).
4. method according to claim 3, wherein, the described first and second decoded signal sections (S_TDAC, the length difference in time interval S_CELP), and carry out described step a) to the time interval one by one for the short time interval to d).
5. according to one of aforesaid right requirement described method, wherein, the described first decoded signal section (S_CELP) passes through the decoding first coded portion (S_COD, CELP) from first demoder (DEC_GES, CELP), and the described second decoded signal section (S_TDAC) is by decoding second coded portion (S_COD, TDAC, S_COD, CELP is TDAC) from second demoder (DEC_TDAC).
6. method according to claim 5, wherein, described second coded portion (S_TDAC) comprises described first coded portion (S_CELP).
7. according to one of aforesaid right requirement described method, wherein, (ENV_CELP, ratio ENV_TDAC) constitutes described identification number (R) by constituting first and second energy envelope line.
8. according to one of aforesaid right requirement described method, wherein, described amplification factor (G) equals described identification number (R).
9. according to one of aforesaid right requirement described method, wherein, (S_COD CELP) constitutes the described first decoded signal (S_CELP), described signal (S_COD by decoded signal, CELP) from a plurality of first scrambler (COD1_A, COD1_B, COD1_C), the described first scrambler (COD1_A, COD1_B is COD1_C) in different frequency domain work.
10. according to one of aforesaid right requirement 5 or 6 described method, wherein, described first demoder (DEC_GES_CELP) constitutes by the CELP demoder.
11. according to one of aforesaid right requirement 5,6 or 10 described method, wherein, described second demoder (DEC_TDAC) constitutes by the conversion demoder.
12. according to one of aforesaid right requirement 5,6,10 or 11 described method, wherein, (DEC_TDAC DEC_CELP) comprises identical frequency domain to described first and second demoders.
13. method that is used for carrying out squelch at the decoded signal that is assigned to a frequency band, described signal is by at corresponding first of the corresponding sub-band of the frequency band decoded signal section (S_CELP_A, S_CELP_B) and the corresponding second decoded signal section (S_TDAC_A, S_TDAC_B) form, described method has following steps:
A. at corresponding sub-band determine the corresponding first decoded signal section the first energy envelope line (ENV_CELP_A, ENV_CELP_B) and the second energy envelope line of the corresponding second decoded signal section (ENV_TDAC_A, ENV_TDAC_B);
B. at corresponding sub-band according to the first and second energy envelope lines relatively constitute corresponding identification number (R_A, R_B);
C. at corresponding sub-band according to corresponding identification number (R) derive corresponding amplification factor (G_A, G_B).
14. method according to claim 13 also has following steps:
If (R_A R_B) does not satisfy determined criterion to d. corresponding identification number, and then (S_TDAC_A, S_TDAC_B) (G_A G_B) multiplies each other with corresponding amplification factor with the described second decoded signal section at corresponding sub-band.
15. an equipment, particularly a kind of communication facilities, it has computing unit (CPU2), and described computing unit (CPU2) is configured to carry out according to the described method of claim 1 to 14.
Applications Claiming Priority (7)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE102005019863.5 | 2005-04-28 | ||
| DE102005019863A DE102005019863A1 (en) | 2005-04-28 | 2005-04-28 | Noise suppression process for decoded signal comprise first and second decoded signal portion and involves determining a first energy envelope generating curve, forming an identification number, deriving amplification factor |
| DE102005028182.6 | 2005-06-17 | ||
| DE102005028182 | 2005-06-17 | ||
| DE200510032079 DE102005032079A1 (en) | 2005-07-08 | 2005-07-08 | Noise suppression process for decoded signal comprise first and second decoded signal portion and involves determining a first energy envelope generating curve, forming an identification number, deriving amplification factor |
| DE102005032079.1 | 2005-07-08 | ||
| PCT/EP2006/061537 WO2006114368A1 (en) | 2005-04-28 | 2006-04-12 | Noise suppression process and device |
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| Publication Number | Publication Date |
|---|---|
| CN1993734A true CN1993734A (en) | 2007-07-04 |
| CN1993734B CN1993734B (en) | 2011-05-18 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2006800005032A Expired - Fee Related CN1993734B (en) | 2005-04-28 | 2006-04-12 | Noise suppression process and device |
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| Country | Link |
|---|---|
| CN (1) | CN1993734B (en) |
| DE (1) | DE102005019863A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102160114B (en) * | 2008-09-17 | 2012-08-29 | 法国电信公司 | Method and device of pre-echo attenuation in a digital audio signal |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6134518A (en) * | 1997-03-04 | 2000-10-17 | International Business Machines Corporation | Digital audio signal coding using a CELP coder and a transform coder |
| ATE302991T1 (en) * | 1998-01-22 | 2005-09-15 | Deutsche Telekom Ag | METHOD FOR SIGNAL-CONTROLLED SWITCHING BETWEEN DIFFERENT AUDIO CODING SYSTEMS |
| US6442275B1 (en) * | 1998-09-17 | 2002-08-27 | Lucent Technologies Inc. | Echo canceler including subband echo suppressor |
-
2005
- 2005-04-28 DE DE102005019863A patent/DE102005019863A1/en not_active Withdrawn
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102160114B (en) * | 2008-09-17 | 2012-08-29 | 法国电信公司 | Method and device of pre-echo attenuation in a digital audio signal |
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| Publication number | Publication date |
|---|---|
| CN1993734B (en) | 2011-05-18 |
| DE102005019863A1 (en) | 2006-11-02 |
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