DC offset and Audio Filtering

Posted by admin
On January 4, 2019

In this post we describe a phenomena called “DC offset” in audio signal and its impact on the quality of audio filtering like noise reduction, echo cancellation and automatic gain control. We say that a signal has a DC offset distortion when the mean amplitude of its waveform is not zero. A normal voice is […]

Acoustic Echo Cancellation Vs. Acoustic Echo Suppression

Posted by admin
On September 2, 2018

Echo is a known problem in telephony and when it appears it dramatically reduces the quality of the audio. In some cases the echo can even turn out to howling effect that generates a deafening noise. To familiarize yourself with the basic terms that relates to echo cancellation, you are invited to read our blog-series […]

PBXMate vs. SoliCall Pro

Posted by admin
On January 10, 2018

If you are a call center, conference bridge provider or any other organization looking to improve audio quality in your telephony using our innovative technology, you might ask yourself which of our products is most suitable for you. Assuming you are not developing your own telephony software our SDKs are not an option but what […]

How to evaluate an echo cancellation algorithm?

Posted by admin
On November 21, 2017

When you encounter an echo problem in your application, network or devices it is obvious you need to introduce an echo canceller. Your next step is to explore at least two possible locations for performing the echo cancellation: cancelling the echo on the client side or doing it on the server side. The decision […]

Echo Cancellation with negative echo tail

Posted by admin
On May 7, 2017

Background Echo path/tail is one of the most fundamental parameters when performing echo cancellation. In previous posts, we elaborated on the importance of echo tail and we also provided a Do It Yourself (DIY) method to calculate the echo tail. In most usage scenarios, the value of the echo tail will be a positive one […]

Time manipulation and its impact on echo cancellation

Posted by admin
On July 1, 2016

Background Time manipulation is a known technique in audio processing. It can be used to either compress the audio (resulting in speed-up) or expand the audio (resulting in slow-down). Usually this is done without altering the pitch and therefore without changing the fundamental signature of the voice.

How can echo suppression badly impact call quality ?

Posted by admin
On January 1, 2016

Background Can phones/soft-phones with built-in echo suppression badly impact the audio quality? Surprising as it may sound the answer is positive. In other words, when a call center, or any other organization, purchase phones with built-in echo suppression it is jeopardizing the overall call quality. In order to analyze the reason for this phenomena we […]

VoIP on Android – volume control

Posted by admin
On August 3, 2015

Background In our previous posts we covered few of the difficulties that Android VoIP developers are facing – for example the challenge in providing high quality echo cancellation. In addition to the echo cancellation, the variety of hardware platforms that are running Android also introduces a challenge in controlling the volume of the voice.

Posted by admin
On May 22, 2015

Background When developing a VoIP application, most implementations use AudioRecord as the foundation class for capturing audio from the microphone. Can this class be used to cancel echo as well ?

Posted by admin
On March 11, 2015

Background Following our previous post on synchronization, in this post we would like to cover a specific aspect of un-synchronized input which causes the speakers to play silence that is not monitored and therefore unknown to the AEC.

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