Bandfilters with FFT on Sampled in-/output

Started by basgoossen in comp.dsp8 years ago 10 replies

Hello all, Currently i am working on echo cancellation software for a voice communication system. and i came across the following problem: I...

Hello all, Currently i am working on echo cancellation software for a voice communication system. and i came across the following problem: I need to analyse and filter frequency's, so i do a FFT i cut off some frequency's and then perform an iFFT to get the filtered signal. This happens on sample's varying between 20ms and 1000ms (2^9 to 2^16). The frequency's that i whant to get rid of are ...


Echo Cancellation Problem (MATLAB)

Started by John McDermick in comp.dsp8 years ago 10 replies

Hello, Could anybody take a look at this matlab script and tell me why MATLABs echo canceller just doesn't cancel the echo in the test...

Hello, Could anybody take a look at this matlab script and tell me why MATLABs echo canceller just doesn't cancel the echo in the test signal I am using. https://skydrive.live.com/redir.aspx?cid=a84b49958d99df9e&resid=A84B49958D99DF9E!102 Thank you.


Echo Cancellation

Started by John McDermick in comp.dsp8 years ago 9 replies

I had a discussion with a collague about echo cancellation. He claims that an echo canceller during double-talk is able to completely remove...

I had a discussion with a collague about echo cancellation. He claims that an echo canceller during double-talk is able to completely remove the far-end speech component in the microphone signal even if the far-end speech component occupies the same frequency as the near-end speech (assuming that the echo canceller has converged and that it doesn't adapt during double-talk) . I claim tha...


Acoustic Echo Cancellation: Question

Started by John McDermick in comp.dsp8 years ago 8 replies

Hello, I have a general question about acoustic echo cancellers. If you look at the power of the echo component in a microphone signal, is...

Hello, I have a general question about acoustic echo cancellers. If you look at the power of the echo component in a microphone signal, is there a point (common for most AECs) where the AEC starts degrading the near-end speech component instead? From my limited experience with AECs it seems that they work great within a narrow range. If the speaker signal becomes too loud compared to ...


Echo cancellation question (again)

Started by John McDermick in comp.dsp8 years ago 8 replies

Hello, I have made a script which slides a time-window over the speaker signal and the microphone signal. For each window update I save...

Hello, I have made a script which slides a time-window over the speaker signal and the microphone signal. For each window update I save the time lag corresponding to the cross correlation peak value. I had expected to see a more or less constant lag, but instead I see that it is increasing over time. See chart here: http://www.nippyzip.com/uploads/111005105627-44838.zip Wouldn't ...


Automatic gain control and acoustic echo cancellation

Started by John McDermick in comp.dsp8 years ago 4 replies

This is a general question about acoustic echo cancellation based on NLMS. If an AEC receives a speaker signal which has been processed by...

This is a general question about acoustic echo cancellation based on NLMS. If an AEC receives a speaker signal which has been processed by an automatic gain control algorithm, will that have any adverse effects on the AEC's performance? If the change in speaker gain level is too sudden or far from being smooth, doesn't that result in the AEC having to re-adapt? Thank you.


How do you define tail length for frequency domain acoustic echo cancellation algorithms?

Started by Mauritz Jameson in comp.dsp7 years ago 3 replies

For an NLMS time-domain algorithm, the tail length is defined as the number of taps of the NLMS filter, right? How is the tail-length defined...

For an NLMS time-domain algorithm, the tail length is defined as the number of taps of the NLMS filter, right? How is the tail-length defined if you are doing your NLMS in the frequency domain by adjusting the amplitudes of a 128-point FFT?


Echo cancellation to share radio channel

Started by Fender123 in comp.dsp7 years ago 19 replies

Reading up a 1988 edition of Lee & Messerschmitt's "Digital Communication", I came across this gem (Ch18 pg 643): "In principle, echo...

Reading up a 1988 edition of Lee & Messerschmitt's "Digital Communication", I came across this gem (Ch18 pg 643): "In principle, echo cancellation could be used to share any medium, such as a radio channel, for the two directions... would be of great practical interest... but unfortunately is impractical in today's technology..." And the punch-line: "However, we cannot rule it out for the fu...


NLMS and ERL above 0dB

Started by Mauritz Jameson in comp.dsp7 years ago 27 replies

Hi I'm playing around with a traditional NLMS algorithm for acoustic echo cancellation. It seems like the NLMS algorithm have a hard time...

Hi I'm playing around with a traditional NLMS algorithm for acoustic echo cancellation. It seems like the NLMS algorithm have a hard time cancelling the echo as soon as the ERL level creeps above 0dB. Is that to be expected? The speaker signal is pure speech (no noise) and I have linearly filtered the speaker signal to have a simulated microphone signal. The adaptive filter order i...


1250MHz ADC

Started by glen herrmannsfeldt in comp.dsp6 years ago 5 replies

While following the discussion about 8b10b coding, I happened to see a page on 10GbaseT. It seems that 1250MHz 7 bit ADCs (and 10 bit DACs) are...

While following the discussion about 8b10b coding, I happened to see a page on 10GbaseT. It seems that 1250MHz 7 bit ADCs (and 10 bit DACs) are required. Much filtering and echo cancellation is done to the signal, so more bits are needed than actually get sent down the line. I haven't followed ADC technology, but that sounds pretty fast. -- glen


Echo cancellation known impulse response

Started by sigmonde in comp.dsp5 years ago 15 replies

I've implemented a conventional echo cancellation solution using LMS , however my application has a known impulse response which is static. Am...

I've implemented a conventional echo cancellation solution using LMS , however my application has a known impulse response which is static. Am I missing a trick here? Any suggestions great fully received. _____________________________ Posted through www.DSPRelated.com


LMS algorithm in fixed point arithmetic

Started by pscall4ram in comp.dsp4 years ago 6 replies

I have been coding a very rudimentary LMS algorithm for Echo cancellation but I am stuck since the code is not working. I have kept the code to...

I have been coding a very rudimentary LMS algorithm for Echo cancellation but I am stuck since the code is not working. I have kept the code to be very simple and yet I am not able to identify where the code is going wrong. Please help me to identify the error in the code. FILE *ref; and FILE *des; contains the same data and ideally when the algorithm converges,there should not be any voi...


Acoustic Echo Cancellation in hostile delay environment

Started by andygough1974 in comp.dsp4 years ago 2 replies

Are there any good techniques for acoustic echo cancellation where the delay between ref and mic drifts either during a call or between...

Are there any good techniques for acoustic echo cancellation where the delay between ref and mic drifts either during a call or between calls? --------------------------------------- Posted through http://www.DSPRelated.com


detecting an echo in DTMF tone in echo canceler

Started by alpha1 in comp.dsp4 years ago 4 replies

I am facing some issue with my echo cancellation module. I am having a correlator and an adaptive filter modules. My correlator will detect...

I am facing some issue with my echo cancellation module. I am having a correlator and an adaptive filter modules. My correlator will detect presence of echo in the DTMF tones and will activate the adaptive filter. The adaptive filter will remove the echo present in the DTMF tones. Activation of adaptive filter is done only if the correlation is above a certain threshold. My issue is t...